HK1251038A1 - Object identification system and method - Google Patents

Description

Object recognition system and method

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to a co-pending U.S. non-provisional patent application entitled "assignment and Use of Guided Surface Wave models on lossy Media" filed on 7.3.2013 and assigned application number 13/789,538 and disclosed on 11.9.2014 as publication number US2014/0252886 a1 and incorporated herein by reference in its entirety. This application is also related to a U.S. non-provisional patent application, also referred to herein as "Excitation and Use of Guided Surface wave models on Lossy Media", filed on 7.3.2013 and designated as application No. 13/789,525 and disclosed on 11.9.2014 as publication No. US2014/0252865 a1, and incorporated herein by reference in its entirety. This application is further directed to a copending U.S. non-provisional patent application entitled "Excitation and Use of guided Surface Wave Modes on Lossy Media," filed on 9/10 2014 and designated as application number 14/483,089, and incorporated herein by reference in its entirety. This application is further directed to a copending U.S. non-provisional patent application entitled "Excitation and Use of Guided Surface Waves" filed on.6/2 2015 and designated application number 14/728,507, which is incorporated herein by reference in its entirety. This application is further directed to a copending U.S. non-provisional patent application entitled "Excitation and Use of guided Surface Waves" filed on.6/2 2015 and designated application number 14/728,492, which is incorporated herein by reference in its entirety.

Background

Radio wave signals have been transmitted for a century using conventional antenna structures. In contrast to radio science, electrical power distribution systems have relied on directing electrical energy along electrical conductors, such as wires. This understanding of the distinction between Radio Frequency (RF) and power transfer has existed since the beginning of the 20th century.

However, Radio Frequency Identification (RFID) systems have used RF energy transmitted from a reader device to a power tag. The tag may affect the transmitted signal to cause a change in the transmitted signal that is detectable by the reader device, or the tag may transmit an RF signal that is detectable by the reader device. In the former case, the reader may be able to determine that the tag is within the operable range of the reader device. In the latter case, the reader may be able to extract a code that uniquely identifies the tag from the signal output by the tag. The range of RFID systems is severely limited. Furthermore, the capability of the tag is limited due to the small amount of available energy, which may be derived from the RF signal transmitted by the reader device.

Drawings

Aspects of the present disclosure may be better understood with reference to the following drawings. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

Fig. 1 is a graph depicting field strength as a function of distance for a guided electromagnetic field and a radiated electromagnetic field.

Fig. 2 is a diagram illustrating a propagation interface having two regions for transmitting guided surface waves according to various embodiments of the present disclosure.

Fig. 3 is a diagram illustrating a guided surface waveguide probe positioned relative to the propagation interface of fig. 2, in accordance with various embodiments of the present disclosure.

Fig. 4 is a graph of examples of near-asymptote and far-asymptote magnitudes of a first order hankel function according to various embodiments of the present disclosure.

Fig. 5A and 5B are diagrams illustrating a composite incident angle of an electric field synthesized by a guided surface waveguide probe according to various embodiments of the present disclosure.

FIG. 6 is a graphical representation illustrating the elevation effect of a charge terminal on the location where the electric field of FIG. 5A intersects the lossy conducting medium at a Brewster angle, according to various embodiments of the present disclosure.

Figure 7 is a graphical representation of an example of a guided surface waveguide probe according to various embodiments of the present disclosure.

Fig. 8A-8C are graphical representations illustrating examples of equivalent image plane models for the guided surface waveguide probes of fig. 3 and 7, according to various embodiments of the present disclosure.

Fig. 9A and 9B are graphical representations illustrating examples of single-line transmission line and classical transmission line models of the equivalent image plane models of fig. 8B and 8C, according to various embodiments of the present disclosure.

Fig. 10 is a flow diagram illustrating an example of adjusting the guided surface waveguide probe of fig. 3 and 7 to launch a guided surface wave along a surface of a lossy conducting medium according to various embodiments of the present disclosure.

Fig. 11 is a graph illustrating an example of a relationship between a wave-front tilt angle and a phase delay of the guided surface waveguide probe of fig. 3 and 7 according to various embodiments of the present disclosure.

Figure 12 is a drawing illustrating an example of a guided surface waveguide probe according to various embodiments of the present disclosure.

Fig. 13 is a graphical representation illustrating a resultant electric field incident at a complex Brewster angle (Brewster) to match a guided surface waveguide at a Hankel (Hankel) intersection distance according to various embodiments of the present disclosure.

Fig. 14 is a graphical representation of an example of the guided surface waveguide probe of fig. 12, according to various embodiments of the present disclosure.

FIG. 15A includes a charge terminal T of a guided surface waveguide probe according to various embodiments of the present disclosure₁Phase delay (phi)_U) Graph of an example of the imaginary and real parts of (c).

Fig. 15B is a schematic diagram of the guided surface waveguide probe of fig. 14, according to various embodiments of the present disclosure.

Figure 16 is a drawing illustrating an example of a guided surface waveguide probe according to various embodiments of the present disclosure.

Fig. 17 is a diagrammatic representation of an example of the guided surface waveguide probe of fig. 16 according to various embodiments of the present disclosure.

Fig. 18A-18C depict examples of receiving structures that may be used to receive energy transmitted in the form of a guided surface wave transmitted through a guided surface waveguide probe, in accordance with various embodiments of the present disclosure.

Fig. 18D is a flow diagram illustrating an example of adjusting a receive structure according to various embodiments of the present disclosure.

Fig. 19 depicts an example of an additional receiving structure that may be used to receive energy transmitted in the form of a guided surface wave transmitted by a guided surface waveguide probe, in accordance with various embodiments of the present disclosure.

FIG. 20A shows a symbol generally representing a guided surface waveguide probe.

Fig. 20B shows a symbol generally representing a guided surface wave receive structure.

Fig. 20C shows a symbol generally representing a guided surface wave receiving structure of the linear probe type.

Fig. 20D shows a symbol generally representing a guided surface wave receiving structure of a tuned resonator type.

Figure 20E shows a symbol generally representing a guided surface wave receiving structure of the magnetic coil type.

FIG. 21 is a schematic diagram of one embodiment of an object recognition system.

FIG. 22 is a schematic diagram of another embodiment of an object identification system.

FIG. 23 is a schematic diagram of a tag that is part of an object identification system.

Fig. 24 is a schematic diagram of first and second object identification systems deployed at adjacent sites.

FIG. 25 is a schematic diagram of an object identification system deployed to identify objects over a wide area.

FIG. 26 is a schematic diagram of a computer system and receiver as part of an object recognition system.

Detailed Description

1. Lead surface transmission line device and signal generation

To begin the discussion, some terminology should be established to provide clarity in the discussion of concepts that follows. First, as embodied herein, a formal distinction is drawn between a radiating electromagnetic field and a guiding electromagnetic field.

As contemplated herein, the radiated electromagnetic field comprises electromagnetic energy emitted from the source structure in the form of waves that are not coupled to the waveguide. For example, a radiated electromagnetic field is typically a field that exits an electrical structure, such as an antenna, and propagates through the atmosphere or other medium without bonding to any waveguide structure. Once a radiated electromagnetic wave leaves an electrical structure, such as an antenna, the radiated electromagnetic wave continues to propagate in a propagation medium (such as air) independent of its source until the radiated electromagnetic wave dissipates, regardless of whether the source continues to operate. Once an electromagnetic wave is radiated, it is not recoverable unless intercepted, and the energy inherent in the radiated electromagnetic wave is never lost if not intercepted. Electrical structures such as antennas are designed to radiate electromagnetic fields by maximizing the ratio of radiation resistance to structural loss resistance. The radiated energy is spread out in space and lost regardless of the presence of the receiver. The energy density of the radiation field is a function of distance due to geometric dispersion. Thus, all forms of the term "radiation" as used herein refer to such forms of electromagnetic propagation.

A guided electromagnetic field is a propagating electromagnetic wave with energy concentrated within or near the boundary between media having different electromagnetic properties. In this sense, a guided electromagnetic field is a field that is coupled to a waveguide and can be characterized as being carried by a current flowing in the waveguide. If there is no load to receive and/or dissipate the energy carried in the guided electromagnetic wave, there is no energy loss other than dissipation in terms of the conductivity of the guide medium. In other words, if there is no load for guiding the electromagnetic wave, there is no energy consumption. Thus, the generator or other source that generates the guided electromagnetic field does not deliver real power unless a resistive load is present. To this end, such generators or other sources are essentially idle until a load is present. This is similar to operating a generator to generate 60hz electromagnetic waves that are transmitted through a power line in the absence of an electrical load. It should be noted that the guided electromagnetic field or wave is equivalent to what is referred to as a "transmission line mode". This is in contrast to radiated electromagnetic waves, in which real power is always supplied to generate the radiated waves. Unlike radiated electromagnetic waves, guided electromagnetic energy does not continue to propagate along a limited length of the waveguide after the energy source is turned off. Thus, all forms of the term "guided" as used herein refer to electromagnetic propagation of such transmission.

Referring now to fig. 1, a graph 100 of field strength in decibels (dB) over any reference in volts/meter as a function of distance in kilometers on a log-dB plot is shown to further illustrate the difference between a radiated electromagnetic field and a guided electromagnetic field. The graph 100 of fig. 1 depicts a guiding field strength curve 103 showing the field strength of the guiding electromagnetic field as a function of distance. This guided field strength curve 103 is substantially identical to the transmission line mode. Furthermore, the graph 100 of fig. 1 depicts a radiated field strength curve 106 that shows the field strength of a radiated electromagnetic field as a function of distance.

Of interest are the shapes of curves 103 and 106 for guided wave and radiation propagation, respectively. The radiated field strength curve 106 is geometrically decreasing (1/d, where d is the distance), which is depicted as a straight line on a log-log scale. On the other hand, the guidance field strength curve 103 hasAnd exhibits a distinctive knee 109 on the log-log scale. The guiding field strength curve 103 and the radiating field strength curve 106 intersect at a point 112, which occurs at the intersection distance. At distances smaller than the crossing distance at the intersection point 112, the field strength of the guided electromagnetic field is at most locations significantly larger than the field strength of the radiated electromagnetic field. At distances greater than the crossing distance, the reality is faciesAnd the opposite is carried out. Thus, the guided field strength curve 103 and the radiated field strength curve 106 further illustrate the fundamental propagation difference between the guided electromagnetic field and the radiated electromagnetic field. For an informal discussion of the difference between a guided electromagnetic field and a radiated electromagnetic field, reference is made to Milligan, T., model Antenna Design, McGraw-Hill, first edition, 1985, pages 8-9, which is incorporated herein by reference in its entirety.

The distinction between the above-mentioned radiated electromagnetic waves and guided electromagnetic waves is easily expressed in form and placed on a strict basis. These two such completely different solutions can be derived from the same linear partial differential equation, the wave equation being analytically derived from the boundary conditions imposed on the problem. The green's function for the wave equation itself contains the difference between the nature of the radiating wave and the guided wave.

In the white space, the wave equation is a differential operator whose eigenfunction possesses a continuum of eigenvalues in the complex wavenumber plane. This Transverse Electromagnetic (TEM) field is known as the radiation field, and those propagating fields are known as "hertzian waves". However, in the presence of a conductive boundary, the wave equation plus boundary condition mathematically produces a spectral representation of wavenumbers, which consists of a sum of a continuum plus a discrete spectrum. For this purpose, reference is made to Sommerfeld, A., "Uberdie Ausbreitung der Wellen in der Drahtlosen Telegraphie," Annalen der Physik, Vol.28, 1909, p.665-736. See also Sommerfeld, A., "Proelements of radiation", published as Physics-characteristics on therapeutic Physics: chapter 6 of the partial differential equation in volume VI, academycpress, 1949, pages 236-289, pages 295-296; collin, R.E. "Hertzian Dipole radiating over a Lossy Earth ear or Sea: Some Early and Late 20th Century semiconductors", IEEE Antennas and Propagation Magazine, Vol.46, No. 2, 4 months 2004, p.64-79; and Reich, H.J., Ordnong, P.F, Krauss, H.L., and Skalik, J.G., Microwave Theory and technology, Van Nostrand,1953, pp.291-293, each of which is incorporated herein by reference in its entirety.

The terms "ground wave" and "surface wave" identify two distinctly different physical propagation phenomena. Surface waves are analytically generated from distinct poles that produce discrete components in the plane spectrum. See, for example, "The Excitation of plane Surface Waves", Cullen, A.L. (Proceedings of The IEE (British), Vol.101, part IV, 8.1954, p.225-235). In this case, the surface wave is regarded as a guided surface wave. The surface wave (in the sense of the lneck-sonofilfel guide wave) is not physically and mathematically identical to the surface wave (in the sense of the alien-norton-FCC) which is now well known with radio broadcasting. These two propagation mechanisms result from excitation of different types of signature spectra (continuum or discrete) on a complex plane. The field strength of a guided surface wave decays exponentially with distance, as illustrated by curve 103 of fig. 1 (more like propagating in a lossy waveguide) and similarly propagating in a radial transmission line, as opposed to the classical hertzian radiation of a ground wave that propagates on a spherical surface, possesses a continuum of characteristic values, falls off geometrically, as illustrated by curve 106 of fig. 1, and is generated by branch-cut (branch-cut) integration. Burrows, as demonstrated by experiments in "The Surface Wave in Radio Propagation over Plane Earth" (Proceedings of The IRE, Vol. 25, p.2, 2 months 1937, p.219-229) and "The Surface Wave in Radio Transmission" (Belllaboratories Record, Vol. 15, 6 months 1937, p.321-324), radiated ground waves but not guided Surface waves.

To summarize the above, firstly, the continuous portion of the wavenumber signature spectrum corresponding to the tangential integral generates a radiation field, and secondly, the sum of the discrete spectrum and the corresponding residual values generated from the poles enveloped by the integral profile generates a non-TEM travelling surface wave, such surface waves being exponentially damped in the direction transverse to propagation. Such a surface wave is a guided transmission line mode. For further explanation, reference is made to Friedman, B., Principles and Techniques of Applied Mathesics, Wiley,1956, pages 214, 283-286, pages 290, and pages 298-300.

In vacuum, the antenna excites a continuum of wave equations, characteristic of the radiation field, having the same phase E_ZAnd H_ΦOf the RF energy propagating outwardsNever be lost. Waveguide probes, on the other hand, excite discrete eigenvalues, thereby creating transmission line propagation. See Collin, R.E., Field Theory of Guided Waves, McGraw-Hill,1960, pp 453, 474-477. Although these theoretical analyses have adhered to the hypothetical possibility of launching an open-guided surface wave on a planar or spherical surface of a lossy homogeneous medium, for more than a century, no known structure exists in the engineering arts to achieve this hypothetical possibility with any practical efficiency. Unfortunately, because of the theoretical analysis set forth above that emerged at the beginning of the 20th century, this theoretical analysis was essentially only theoretical, and there has not been a known structure to actually achieve the emission of open-guided surface waves on planar or spherical surfaces of lossy homogeneous media.

According to various embodiments of the present disclosure, various guided surface waveguide probes are described that are configured to excite an electric field that couples to guided surface waveguide modes along a surface of a lossy conducting medium. Such a guided electromagnetic field is substantially mode-matched in magnitude and phase to the guided surface wave mode on the surface of the lossy conducting medium. Such guided surface wave modes may also be referred to as zeneck (Zenneck) waveguide modes. Due to the fact that the resulting field excited by the guided surface waveguide probe described herein is substantially mode-matched to the guided surface waveguide mode on the surface of the lossy conducting medium, a guided electromagnetic field in the form of a guided surface wave is emitted along the surface of the lossy conducting medium. According to one embodiment, the lossy conducting medium comprises a terrestrial medium, such as the earth.

Referring to FIG. 2, a Propagation interface is shown that provides a check of the boundary value solution for the Maxonw (Maxwell's) equation derived by Jonathan Zenneck in 1907 as set forth in its paper Zenneck, J., "On the Propagation of plant Electromagnetic Waves Along a Flat connection surface and the r relationship to Wireless Telegraphy", Annalen der Physik, series 4, Vol.23, 9/20/1907, pages 846-866. Fig. 2 depicts the cylindrical coordinates for propagating a wave radially along the interface between the lossy conducting medium designated as region 1 and the insulator designated as region 2. The region 1 may comprise, for example, any lossy conducting medium. In one example, such a lossy conducting medium may comprise a terrestrial medium, such as the earth or other medium. Region 2 is a second medium that shares a boundary interface with region 1 and has different composition parameters relative to region 1. Region 2 may comprise, for example, any insulator, such as atmospheric air or other medium. The reflection coefficient of such boundary interfaces becomes zero only for incidence at the composite brewster angle. See Stratton, J.A., electronic Theory, McGraw-Hill,1941, page 516.

According to various embodiments, the present disclosure sets forth various guided surface waveguide probes that generate an electromagnetic field that is substantially mode-matched to a guided surface waveguide mode on a surface of a lossy conducting medium containing region 1. According to various embodiments, such electromagnetic fields substantially synthesize a wavefront incident at a complex brewster angle of the lossy conducting medium, which may result in zero reflection.

For further explanation, in region 2, where e is assumed^jωtThe field variation, and where ρ ≠ 0 and z ≧ 0 (where z is the perpendicular coordinate normal to the surface of region 1, and ρ is the radial dimension in the cylindrical coordinate), the exact solution of the Zernike's closed form of the Makeshift equation that satisfies the boundary conditions along the interface is represented by the following electric and magnetic field components:

in region 1, where e is assumed^jωtMakeshift's square with field variation where ρ ≠ 0 and z ≦ 0, satisfying boundary conditions along the interfaceThe exact solution of the zernike closure form of the equation is represented by the following electric and magnetic field components:

in these expressions, z is a vertical coordinate normal to the surface of zone 1, and ρ is a radial coordinate,is a complex argument of the second and nth order, the hank function, u₁Is a propagation constant in the positive vertical (z) direction in region 1, u₂Is the propagation constant, σ, in the vertical (z) direction in region 2₁Omega is the conductivity of the region 1 and is equal to 2 pi f, where f is the frequency of excitation, epsilon_oPermittivity of being vacuum,. epsilon₁Is the permittivity of region 1, a is the source constant applied by the source, and γ is the surface wave radial propagation constant.

The propagation constants in the ± z-direction are determined by separating the wave equation above and below the interface between region 1 and region 2 and applying boundary conditions. This is given in region 2

And it is found in the region 1 that,

u₁＝-u₂(ε_r-jx) (8)

the radial propagation constant γ is given by

This is a compound expression where n is the compound refractive index, which is given by

In all of the above equations, the equation is,

wherein epsilon_rRelative permittivity, σ, of the region 1₁Is the conductivity of the region 1, epsilon_oIs a vacuum permittivity and_oincluding the magnetic permeability of the vacuum. Thus, the generated surface wave propagates parallel to the interface and decays exponentially perpendicular to the interface. This is called the fade.

Thus, equations (1) - (3) can be viewed as cylindrically symmetric, radially propagating waveguide modes. See Barlow, H.M. and Brown, J., Radio Surface Waves, Oxford University Press,1962, pages 10-12, pages 29-33. The present disclosure details the structure that excites this "open boundary" waveguide mode. In particular, according to various embodiments, a guided surface waveguide probe is provided with appropriately sized charge terminals that are positioned with respect to the boundary interface between region 2 and region 1 using voltage and/or current feeds. This may be better understood with reference to fig. 3, which shows an example of a guided surface waveguide probe 200a that includes a charge terminal T1 elevated above a lossy conducting medium 203 (e.g., earth) along a vertical axis z that is normal to a plane provided through the lossy conducting medium 203. Lossy conducting medium 203 constitutes region 1 and second medium 206 constitutes region 2 and shares a boundary interface with lossy conducting medium 203.

According to one embodiment, the lossy conducting medium 203 may comprise a terrestrial medium, such as a planetary earth. To this end, such land boundary media encompass all structures or formations included on such structures, whether natural or man-made. For example, such terrestrial media may contain natural elements such as rocks, soil, sand, fresh water, sea water, trees, plants, and all other natural elements that make up our planet. Additionally, such land boundary media may contain man-made elements such as concrete, asphalt, building materials, and other man-made materials. In other embodiments, the lossy conducting medium 203 may comprise some medium other than earth, whether naturally occurring or man-made. In other embodiments, the lossy conducting medium 203 may comprise other media, such as man-made surfaces and structures, such as automobiles, airplanes, man-made materials (such as plywood, plastic rolls, or other materials), or other media.

In the case where the lossy conducting medium 203 comprises a land-bound medium or the earth, the second medium 206 may comprise the atmosphere above ground. Thus, the atmosphere may be referred to as an "atmospheric medium" which contains air and other elements that make up the earth's atmosphere. In addition, the second medium 206 may possibly contain other media relative to the lossy conducting medium 203.

Guided surface waveguide probe 200a includes a feed network 209 that couples excitation source 212 to charge terminal T1 via, for example, a vertical feed line conductor. According to various embodiments, charge Q1 is applied to charge terminal T1 to synthesize an electric field based on the voltage applied to terminal T1 at any given instant. Dependent on the angle of incidence (theta) of the electric field (E)_i) It is possible to substantially mode-match the electric field to the guided surface waveguide mode on the surface of the lossy conducting medium 203 containing region 1.

The Leontovich impedance boundary condition between region 1 and region 2 can be expressed as a function of the Leontovich impedance boundary condition by considering the Zernike closed-form solutions of equations (1) - (6)

WhereinIs a unit normal vector in the positive vertical (+ z) direction, andis the magnetic field strength in region 2, which is represented by equation (1) above. Equation (13) implies: the electromagnetic fields specified in equations (1) - (3) may produce radial surface current densities along the boundary interface, where the radial surface current densities may be specified by

Wherein A is a constant. In addition, it should be noted that, close to the guide surface waveguide probe 200 (for ρ < < λ), the above equation (14) has the following behavior

The minus sign means: when the current (I) is sourced_o) When flowing vertically upward as illustrated in fig. 3, current "near" ground flows radially inward. By pairs H_ΦIs "close" to the field match, can be determined

Wherein in equations (1) - (6) and (14), q₁＝C₁V₁. Thus, the radial surface current density of equation (14) can be restated as follows

The fields represented by equations (1) - (6) and (17) have the property of transmission line mode shape coupling to the lossy interface rather than the radiated field associated with ground wave propagation. See Barlow, H.M. and Brown, J., Radio Surface Waves, Oxford university Press,1962, pages 1-5.

Here, a review of the properties of the hankel functions used in equations (1) - (6) and (17) is provided for these solutions to the wave equation. It is observed that the first and second classes and the nth order hankel function are complex combinations of standard Bessel (Bessel) functions defined as the first and second classes

The functions respectively representing radial inwardAnd radially outwardlyA propagating cylindrical wave. The definition is similar to the relation e^±jxCos x ± j sin x. See, e.g., Harrington, r.f.,Time-Harmonic FieldsMcGraw-Hill,1961, pages 460-463.

ThatFor the outgoing wave, it can be identified from the large argument asymptotic behavior of the outgoing wave, from J_n(x) And N_n(x) Is directly obtained by defining the number of stepsAnd (5) obtaining the product. Distancing of the waveguide probe from the guide surface:

when multiplied by e^jωtWhen it is an outwardly propagating cylindrical wave, the outwardly propagating cylindrical wave hasForm e of spatial variation^j(ωt-kρ). A first order (n ═ 1) solution can be determined from equation (20a) as

Near the guide surface waveguide probe (for ρ < < λ), the first and second classes of hankel functions behave as

Note that these asymptotic expressions are complex quantities. When x is a real quantity, equations (20b) and (21) are out of phaseWhich corresponds to an additional phase advance or "phase advance" of 45 deg. or equivalently to lambda/8. The near and far asymptotes of the first-order hankel functions of the second class have hankel "crossover" or transition points, where these asymptotes are at ρ ═ R_xHave equal magnitude at the distance of (a).

Thus, beyond the hankel crossing point, a "far" representation of the hankel function is more dominant than a "close" representation. The distance to the hankel intersection (or hankel intersection distance) can be determined by equating equations (20b) and (21) for j γ ρ and for R_xAnd solving to obtain the product. At x ═ σ/ω ε_oIn the case of (2), it can be seen that the distance from the Hankel functionThe asymptotes and the approximation hankel function asymptotes are frequency dependent, with the hankel crossing points moving outward as the frequency decreases. It should also be noted that the hankel function asymptote may also vary as the conductivity (σ) of the lossy conducting medium changes. For example, the conductivity of soil may change as weather conditions change.

Referring to fig. 4, shown is the region 1 conductivity and relative permittivity ∈ for σ ═ 0.010mhos/m at an operating frequency of 1850kHz_rAn example of a plot of the magnitudes of the first-order hank functions of equations (20b) and (21) as 15. Curve 115 is the magnitude of equation (20b) away from the asymptote, and curve 118 is the magnitude of equation (21) near the asymptote, where the Hankel crossing point 121 occurs at R_xAt a distance of 54 feet. Although the magnitude is the same, there is a phase offset between the two asymptotes at the hankel crossing 121. It can also be seen that: the hankel crossing distance is much smaller than the wavelength of the operating frequency.

Considering the electric field components derived from equations (2) and (3) solved by the Zernike closed form in region 2, see E_zAnd E_ρIs progressively transmitted into

Wherein n is the complex refractive index of equation (10) and θ_iIs the angle of incidence of the electric field. In addition, the vertical component of the mode-matching electric field of equation (3) is transferred asymptotically to

Which is linearly proportional to the free charge of the isolated component of the capacitance at terminal voltage of the rising charge electrons, q_{Freedom of movement}＝C_{Freedom of movement}×V_T。

For example, the elevated charge terminal T in FIG. 3₁Height H of₁Influencing the chargeTerminal T₁The amount of upper free charge. When the charge terminal T₁Most of the charge Q on the terminals when near the ground plane of region 1₁Is "" bound "". When the charge terminal T₁At the rise, bound charge decreases until charge terminal T₁To a height at which substantially all of the isolated charges are free.

Charge terminal T₁The advantage of increasing the capacitance elevation is: elevated charge terminal T₁The charge on is further removed from the ground plane resulting in an increased amount of free charge q_{Freedom of movement}Coupling energy into the guided surface waveguide mode. When the charge terminal T₁Moving away from the ground plane, the charge distribution becomes more evenly distributed about the surface of the terminal. Amount of free charge and charge terminal T₁Is concerned with the self-capacitance of.

For example, the capacitance of a ball terminal may be expressed as a function of the height of the solid above the ground plane. The capacitance of a sphere at a physical height h above the ideal ground is given by

C_{Elevated ball}＝4πε_oa(1+M+M²+M³+2M⁴+3M⁵+…)， (24)

Wherein the diameter of the sphere is 2a, and wherein M ═ a/2h, wherein h is the height of the ball terminal. As can be seen, the increase in terminal height h reduces the capacitance C of the charge terminal. It can be verified that the charge terminal T is connected₁Is at a height of about four times the diameter (4D-8 a) or more, the charge distribution is substantially uniform about the ball terminal, which may improve coupling into the guided waveguide mode.

The self-capacitance of the conductive sphere can be passed through C-4 pi epsilon with sufficiently isolated terminals_oa is approximated, where a is the radius of the sphere (in meters), and the self-capacitance of the disk can be approximated by C-8 ∈_oa, where a is the radius of the disk (in meters). Charge terminal T₁May comprise any shape such as a sphere, disc, cylinder, cone, ring, cage, one or moreRings or any other random shape or combination of shapes. The equivalent spherical diameter can be determined and used for the charge terminal T₁Positioning of (3).

This can be further understood with reference to the example of fig. 3, in which the charge terminal T₁Elevated above the lossy conducting medium 203 by h_p＝H₁At a physical height of (a). To reduce the effect of "bound" charges, the charge terminal T₁Can be positioned at the charge terminal T₁At least four times the solid height of the spherical diameter (or equivalent spherical diameter) in order to reduce the bound charge effect.

Referring next to FIG. 5A, a charge terminal T through FIG. 3 is shown₁Increased charge Q on₁Ray-optical interpretation of the electric field generated. As in optics, minimizing reflection of the incident electric field may improve and/or maximize energy coupling into the guided surface waveguide modes of the lossy conducting medium 203. For an electric field (E) polarized parallel to the plane of incidence (non-boundary interface)_||) In other words, the amount of reflection of an incident electric field can be determined using the Fresnel reflection coefficient, which can be expressed as

Wherein theta is_iIs a conventional angle of incidence measured relative to the surface normal.

In the example of FIG. 5A, the ray-optics interpretation shows the angle of incidence θ_iOf the incident plane of the polarized incident field, the angle of incidence being relative to the surface normalTo measure. When gamma is_||(θ_i) At 0, there is no reflection of the incident electric field, and so the incident electric field will be fully coupled into the guided surface waveguide mode along the surface of the lossy conducting medium 203. It can be seen that the numerator of equation (25) becomes zero at an incident angle of

Where x is σ/ω ε_o. The composite angle of incidence (theta)_i,B) Referred to as the brewster angle. Referring back to equation (22), it can be seen that the same composite brewster angle (θ) exists in equations (22) and (26)_i,B) And (4) relationship.

As illustrated in fig. 5A, the electric field vector E may be depicted as an incoming non-uniform plane wave, polarized parallel to the plane of incidence. The electric field vector E can be generated from independent horizontal and vertical components as

Geometrically, the illustration in FIG. 5A implies that the electric field vector E can be derived from

E_ρ(ρ,z)＝E(ρ,z)cosθ_iAnd (28a)

This means that the field ratio is

A generalized parameter W, referred to as "wavefront slope," is expressed herein as the ratio of the horizontal electric field component to the vertical electric field component, which is derived from

Or (30a)

It is complex and has both magnitude and phase. For an electromagnetic wave in region 2, the wavefront tilt angle (Ψ) is equal to the angle between the normal of the wavefront at the boundary interface with region 1 and the tangent of the boundary interface. This can be easily seen in fig. 5B, which fig. 5B illustrates the isophase surface of an electromagnetic wave and its normal to a radial cylindrical guided surface wave. At the boundary interface with the ideal conductor (z-0), the wavefront normal is parallel to the tangent of the boundary interface, causing W-0. However, in the case of lossy media, there is a wavefront tilt W, because at z-0, the wavefront normal is not parallel to the tangent of the boundary interface.

Applying equation (30b) to the guided surface wave yields

At an angle of incidence equal to the composite brewster angle (θ)_i,B) In the case of (2), the Fresnel reflection coefficient of equation (25) disappears as shown by

By adjusting the composite field ratio of equation (22), the incident field can be synthesized to be incident at a composite angle at which reflections are reduced or eliminated. This ratio is established asA resultant electric field is generated that is incident at the complex brewster angle, causing the reflections to disappear.

The concept of electrically effective height may provide further insight into synthesizing an electric field with a complex angle of incidence using the guided surface waveguide probe 200. For having h_pA monopole of physical height (or length), an electrically effective height (h)_eff) Has been defined as

Because the expression depends on the magnitude and phase of the source distribution along the structure, the effective height (or length) is substantially complex. The integral of the distributed current I (z) of the structure is over the physical height (h) of the structure_p) Is normalized to the ground current (I) flowing upward through the base (or input) of the structure₀). The distribution of current along the structure can be represented by

I(z)＝I_Ccos(β₀z)， (34)

wherein beta is₀Is the propagation factor of the current propagating on the structure. In the example of FIG. 3, I_CIs the current distributed along the vertical structure of the guided surface waveguide probe 200 a.

For example, consider a feed network 209 that includes a low-loss coil (e.g., a spiral coil) at the bottom of the structure and a connection between the coil and a charge terminal T₁A vertical feed line conductor in between. The phase delay due to the coil (or spiral delay line) is θ_c＝β_pl_CWherein the entity length is l_CAnd a propagation factor of

Wherein V_fIs a structural velocity factor, λ₀To supply a wavelength at a frequency, and_pis composed of a speed factor V_fThe resulting propagation wavelength. With respect to the earth (rod) current I₀The phase delay is measured.

In addition, the length l of the conductor along the vertical feed line_wMay be delayed by theta_y＝β_wl_wto give wherein β_wIs the propagation phase constant of the vertical feed line conductor. In thatIn some embodiments, the spatial phase delay may be by θ_y＝β_wh_pTo approximate, because of the physical height h of the guided surface waveguide probe 200a_pAnd length l of vertical feeding line conductor_wThe difference between them is compared with the wavelength (lambda) at the supply frequency₀) Much smaller. Thus, the total phase delay across the coil and the vertical feed line conductor is Φ ═ θ_c+θ_yAnd the current fed from the bottom of the solid structure to the top of the coil is

I_C(θ_c+θ_y)＝I₀e^jΦ， (36)

Wherein the total phase delay Φ is with respect to the ground (rod) current I₀To measure. Thus, for the height h of the body therein_p<<λ₀The electrically effective height of the guided surface waveguide probe 200 can be approximated by

Composite effective height (h) of monopole at angle (or phase shift) of phi_eff＝h_p) May be adjusted so that the source field matches the guided surface waveguide mode and so that the guided surface wave is launched onto the lossy conducting medium 203.

In the example of FIG. 5A, ray optics is used to illustrate the cross-over distance (R) in Hankel_x) With a composite brewster angle of incidence (θ) at 121_i,B) The incident electric field (E) of (2). Recall from equation (26) that for lossy conducting media, the brewster angle is complex and is specified by

Electrically, the geometric parameter being determined by the charge terminal T₁Electrical effective height (h) of_eff) Associating by

R_xtanψ_i,B＝R_x×W＝h_eff＝h_pe^jΦ， (39)

Wherein psi_i,B＝(π/2)-θ_i,BIs the brewster angle measured from the surface of the lossy conducting medium. For coupling into a guided surface waveguide mode, the slope of the electric field at the hankel crossing distance can be expressed as the ratio of the electrically effective height to the hankel crossing distance

Because of the physical height (h)_p) And the Hankel crossing distance (R)_x) All are actual quantities, so at the Hankel crossing distance (R)_x) Where the desired guide plane wave tilt angle (Ψ) is equal to the composite effective height (h)_eff) Phase (Φ). This implies that: by varying the phase at the supply point of the coil, and thus the phase shift in equation (37), the phase Φ of the composite effective height can be manipulated to match the wavefront tilt angle Ψ of the guided surface waveguide mode at the hankel intersection 121: phi psi.

In fig. 5A, a right triangle is depicted, having a length R along the surface of the lossy conducting medium_xAnd the composite brewster angle psi measured between ray 124 and surface 127 of lossy conducting medium_i,BThe ray 124 is at R_xAt the hank crossing point 121 and the charge terminal T₁And the surface of the lossy conducting medium is between the hank crossing point 121 and the charge terminal T₁In the meantime. At the charge terminal T₁Positioned at a substantial height h_pAnd excited with charges having an appropriate phase delay Φ, the resulting electric field crosses at a distance R of Hankel_xUsing a lossy conducting medium boundary and incident at a brewster angle. Under these conditions, guided surface waveguide modes can be excited with no or substantially negligible reflection.

If it is not changed to be effectiveHeight (h)_eff) In the case of a phase shift Φ, the charge terminal T₁The resulting electric field intersects the lossy conducting medium 203 at a reduced distance from the guided surface waveguide probe 200 at the brewster angle. FIG. 6 graphically illustrates reducing the charge terminal T₁The effect of the physical height of (a) on distance, wherein the electric field is incident at the brewster angle. At a height of h₃Via h₂Is reduced to h₁At the time, the point at which the electric field intersects a lossy conducting medium (e.g., the earth) at the brewster angle moves closer to the charge terminal location. However, as indicated by equation (39), the charge terminal T₁Height H of₁(FIG. 3) should be at or above the physical height (h)_p) So as to excite the far component of the hank function. By positioning at an effective height (h)_eff) A charge terminal T at or above the effective height₁The lossy conducting medium 203 may be at a Brewster angle of incidence (psi)_i,B＝(π/2)-θ_i,B) Irradiated Dahankel cross-distance (R)_x)121 or over the hankel crossing distance, as illustrated in fig. 5A. To reduce or minimize the charge terminal T₁The height of the bound charge above should be referred to as the charge terminal T as above₁Is at least four times the spherical diameter (or equivalent spherical diameter).

The guided surface waveguide probe 200 may be configured to establish an electric field with a wave plane tilt corresponding to a wave illuminating the surface of the lossy conducting medium 203 at a complex brewster angle, thereby passing through at R_xAt (or beyond) hankel crossing 121 to substantially mode-match the guided surface wave mode to excite radial surface currents.

Referring to fig. 7, there is shown a structure including a charge terminal T₁A graphical representation of an example of a guided surface waveguide probe 200 b. AC source 212 acts as a charge terminal T₁Coupled to the guided surface waveguide probe 200b via a feed network 209 (fig. 3) that contains a coil 215, such as, for example, a helical coil. In other embodiments, the AC source 212 may be inductively coupled to the coil 215 via a primary coil. In some embodiments, an impedance matching network may be included toImproving and/or maximizing the coupling of the AC source 212 to the coil 215.

As shown in FIG. 7, the guided surface waveguide probe 200b may include an upper charge terminal T₁(e.g., at height h)_pA sphere) positioned along a vertical axis z substantially perpendicular to a plane provided through the lossy conducting medium 203. A second medium 206 is over the lossy conducting medium 203. Charge terminal T₁With self-capacitance C_T. During operation, depending on the voltage applied to the terminal T at any given instant₁Voltage of (2) to charge Q₁Applied to a terminal T₁。

In the example of fig. 7, the coil 215 is coupled at a first end to a ground bar 218 and to a charge terminal T via a vertical feed line conductor 221₁. In some embodiments, and charge terminal T₁May be adjusted using a tap (tap)224 of the coil 215, as shown in fig. 7. The coil 215 may be excited at an operating frequency by the AC source 212 via a tap 227 at a lower portion of the coil 215. In other embodiments, the AC source 212 may be inductively coupled to the coil 215 via a primary coil.

The configuration and tuning of guided surface waveguide probe 200 is based on various operating conditions, such as transmission frequency, conditions of lossy conducting medium (e.g., soil conductivity σ and relative permittivity ε_r) And a charge terminal T₁The size of (2). The refractive index can be calculated from equations (10) and (11) as

Where x is σ/ω ε_oAnd ω 2 pi f. Conductivity sigma and relative permittivity epsilon_rCan be determined by experimental measurements of the lossy conducting medium 203. Composite brewster angle (theta) measured from surface normal_i,B) Can also be determined from equation (26)

Or as measured from the surface as shown in FIG. 5A

At the Hankel crossing distance (W)_Rx) The wave front tilt at (a) can also be derived using equation (40).

The hankel cross-distance may also be equalized for R by equalizing the magnitudes of equations (20b) and (21) for-j γ ρ_xSolved, as illustrated in fig. 4. The electrically effective height may then be determined using the Hankel intersection distance and the composite Brewster angle based on equation (39)

h_eff＝h_pe^jΦ＝R_xtanψ_i,B。 (44)

As can be seen from equation (44), the composite effective height (h)_eff) Includes a charge terminal T₁Height (h) of_p) Associated magnitude and cross distance (R) to Hankel_x) The phase delay (phi) associated with the wave front tilt angle (psi). Using these variables and the selected charge terminal T₁Configuration, it is possible to determine the configuration of the guided surface waveguide probe 200.

By positioning at physical height (h)_p) A charge terminal T at or above the physical height₁Feed network 209 (fig. 3) and/or connecting the feed network to charge terminal T₁Can be adjusted to connect the charge terminal T to₁Charge Q on₁Is matched to the angle (Ψ) of the wave front tilt (W). Charge terminal T₁Can be selected to provide a sufficiently large surface for the charge Q₁Is applied to the terminal. In general, the charge terminal T is intended to be₁Made as large as practical. Charge terminal T₁Should be large enough to avoid ionization of the surrounding air, which could lead to electrical discharge or ignition around the charge terminalsAnd (4) flower.

Phase delay theta of spiral wound coil_cCan be determined from the Mascara equation, as has been discussed by Corum, K.L. and J.F.Corum, "RF Coils, magnetic detectors and Voltage magnetic resonance models," Microwave Review, Vol.7, No. 2, 9/2001, pages 36-45, which is incorporated herein by reference in its entirety. For having H/D>1, the ratio of the propagation velocity (v) of the wave to the speed of light (c) along the longitudinal axis of the coil, or "velocity factor", is given by

Where H is the axial length of the solenoidal helix, D is the coil diameter, N is the number of turns of the coil, s H/N is the turn-to-turn spacing (or helical pitch) of the coil, and λ_oIs the vacuum wavelength. Based on this relationship, the electrical length or phase delay of the spiral coil is derived from

If the helix is wound in a helical manner or if the helix is short and wide, the principle is the same, but V_fAnd theta_cIs easier to be obtained by experimental measurement. Expressions for the characteristic (wave) impedance of a spiral transmission line have also been derived

Spatial phase delay of structure theta_yThe traveling wave phase delay of the vertical feed line conductor 221 can be used for determination (fig. 7). The capacitance of a cylindrical vertical conductor above an ideal ground plane can be expressed as

Farad (48)

Wherein h is_wIs the vertical length (or height) of the conductor, and a is the radius (in mk). Like the spiral coil, the traveling wave phase delay of the vertical feed line conductor can be obtained by

wherein beta is_wIs the propagation phase constant of the conductor of the vertical feed line, h_wIs the vertical length (or height), V, of the vertical feed line conductor_wIs a velocity factor, λ, on the wire₀To supply a wavelength at a frequency, and_wis composed of a speed factor V_wThe resulting propagation wavelength. For a uniform cylindrical conductor, the velocity factor is V_wA constant of 0.94, or a constant in the range of about 0.93 to about 0.98. If the antenna mast is considered as a uniform transmission line, the average characteristic impedance can be approximated by

Wherein V is for a uniform cylindrical conductor_w0.94 and a is the radius of the conductor. An alternative expression for the characteristic impedance of a single-wire feed line, which has been used in the complementary radio literature, can be derived from

Equation (51) implies Z for a single-wire feeder_wVarying with frequency. The phase delay may be determined based on the capacitance and the characteristic impedance.

Using a charge terminal T positioned on a lossy conducting medium 203 as shown in figure 3₁The feed network 209 may be adjusted to take advantage of the composite effective height (h)_eff) Excites the charge terminal T₁The phase shift is equal to the wave plane tilt angle (Ψ) or Φ at the hankel intersection distance (Ψ). When this condition is satisfied, the voltage is passed through the charge terminal T₁Charge oscillation Q on₁The resulting electric field couples into a guided surface waveguide mode traveling along the surface of lossy conducting medium 203. For example, if Brewster's angle (θ)_i,B) Phase delay (θ) associated with the vertical feed line conductor 221 (fig. 7)_y) And the configuration of coil 215 (fig. 7) is known, the position of tap 224 (fig. 7) can be determined and adjusted to oscillate charge Q with phase phi psi₁Applied to the charge terminal T₁The above. The position of the tap 224 may be adjusted to maximize the coupling of the traveling surface wave into the guided surface waveguide mode. Excess coil length beyond the location of the tap 224 may be removed to reduce capacitive effects. The vertical wire height and/or geometric parameters of the helical coil may also be varied.

Coupled with the guided surface waveguide mode on the surface of the lossy conducting medium 203, the guided surface waveguide probe 200 can be tuned for relative coupling with the charge terminal T₁Charge Q on₁The standing wave resonance of the associated composite image plane is improved and/or optimized. By doing so, the performance of the guided surface waveguide probe 200 can be adjusted for the charge terminal T₁Increased and/or maximum voltage (and thus charge Q)₁). Referring back to fig. 3, the effect of the lossy conducting medium 203 in region 1 can be examined using image theory analysis.

Physically, elevated charge Q placed on an ideal conducting plane₁Attracting free charge on the ideal conducting plane, which is then at an elevated charge Q₁The lower region is "piled up". The resulting distribution of "bound" current on the ideal conducting plane resembles a bell-shaped curve. Elevated charge Q₁The superposition of the potential of (c) plus the potential of the induced "built-up" charge under the elevated charge contributes to the zero equipotential surface of the ideal conducting plane. The classical concept of image charge can be used to obtain a boundary value problem describing the field in the region above the ideal conduction planeThe solution, in which the field from the elevated charge is superimposed with the field from the corresponding "image" charge below the ideal conducting plane.

This analysis can also be made by assuming the effective image charge Q of the guided surface waveguide probe 200₁The presence of' is used with respect to the lossy conducting medium 203. Effective image charge Q₁' AND charge terminal T₁Charge Q on₁The conductive image ground planes 130 coincide, as illustrated in fig. 3. However, the image charge Q₁' not only at a certain true depth but also with the charge terminal T₁Primary source charge Q of₁180 deg. out of phase as is the case for these charges in the case of ideal conductors. Instead, the lossy conducting medium 203 (e.g., a terrestrial medium) has a phase-shifted image. In other words, the image charge Q₁' at a compound depth below the surface (or physical boundary) of the lossy conducting medium 203. For a discussion of composite image depth, reference is made to Wait, j.r., "complex image Theory-viewed", IEEE Antennas and presentation magic, volume 33, phase 4, month 8 1991, pages 27-29, which is incorporated herein by reference in its entirety.

Instead of being at equal charge Q₁Height of (H)₁) Image charge Q at depth of₁' conductive image ground plane 130 (representing an ideal conductor) is located at a composite depth of z-d/2 and image charge Q₁' occurs at a compound depth (i.e., the "depth" has a magnitude and a phase), which is represented by-D₁＝-(d/2+d/2+H₁)≠H₁And (6) obtaining. For a vertically polarized source on the earth,

wherein

As indicated in equation (12). The recombination interval of the image charges then implies: the external field will experience additional phase shift that is not encountered when the interface is dielectric or ideal conductor. In a lossy conducting medium, the wavefront normal is parallel to the tangent of the conductive image ground plane 130 at z ═ d/2, rather than at the boundary interface between region 1 and region 2.

Consider the situation illustrated in fig. 8A, where the lossy conducting medium 203 is a finite conducting earth 133 having a solid boundary 136. The limited conductive earth 133 may be replaced by an ideal conductive image ground plane 139 (shown in fig. 8B) that is located at a composite depth z below the solid boundary 136₁To (3). This equivalent representation exhibits the same impedance when looking down to the interface at the physical boundary 136. The equivalent representation of fig. 8B can be modeled as an equivalent transmission line, as shown in fig. 8C. The cross-section of the equivalent structure is represented as a (z-oriented) end-loaded transmission line, where the impedance of the ideal conducting image plane is a short circuit (z-oriented)_s0). Depth z₁The image ground plane impedance z seen by looking down at the earth can be equated to the TEM wave impedance seen by the transmission line to figure 8C_inAnd then the judgment is made.

In the case of fig. 8A, the propagation constant and the wave intrinsic impedance in the upper region (air) 142 are

In the lossy earth 133, the propagation constant and the wave natural impedance are

For normal incidence, the equivalent representation of FIG. 8B is equivalent to a TEM transmission line whose characteristic impedance is that of air (z)₀) And propagation constant is gamma₀And has a length z₁. Thus, the image ground plane impedance z seen at the interface for the shorted transmission line of fig. 8C_inIs obtained by

Z_in＝Z_otanh(γ_oz₁) (59)

Image ground plane impedance z to be associated with the equivalent model of FIG. 8C_inEquivalent Normal incident wave impedance of FIG. 8A and for z₁Solved to obtain the distance to the short circuit (the ideal conductive image ground plane 139) as

Where only the first term of the series expansion of the inverse hyperbolic tangent is considered for this approximation. Note that in the air region 142, the propagation constant is γ_o＝jβ_oThus Z is_in＝jZ_otanβ_oz₁(it is true z)₁Pure imaginary quantity of) but if σ ≠ 0, then z_eIs a composite value. Therefore, only in z₁At a compound distance, z_in＝z_e。

Because the equivalent representation of FIG. 8B includes an ideal conductive image ground plane 139, the image depth of charge or current located at the earth's surface (solid boundary 136) is equal to the distance z on the other side of the image ground plane 139₁Or 2 xz below the earth's surface (at z 0)₁. Thus, the distance to the desired conductive image ground plane 139 can be approximated by

In addition, the "image charge" will be equal and opposite to the "true charge, thus at depth z₁The potential of the ideal conductive image ground plane 139 at-d/2 will be zero.

If charge Q₁Elevated above the surface of the earth by a distance H₁As illustrated in fig. 3, the image charge Q₁' residing below the surface D₁＝d+H₁Or d/2+ H below the image ground plane 130₁At the composite distance of (a). The guided surface waveguide probe 200B of fig. 7 can be modeled as an equivalent single line transmission line image plane model, which can be based on the ideal conductive image ground plane 139 of fig. 8B. Fig. 9A shows an example of an equivalent single-line transmission line image plane model, and fig. 9B illustrates an example of an equivalent classical transmission line model, which includes the shorted transmission lines of fig. 8C.

In the equivalent image plane model of fig. 9A and 9B, Φ is θ_y+θ_cTraveling wave phase delay, θ, of guided surface waveguide probe 200 referenced to earth 133 (or lossy conducting medium 203)_c＝β_pH is the electrical length of the coil 215 (FIG. 7) which has a physical length H (in degrees), θ_y＝β_wh_wIs the electrical length of the vertical feed line conductor 221 (fig. 7) having a physical length h_w(in degrees) and θ_d＝β₀d/2 is the phase shift between the image ground plane 139 and the physical boundary 136 of the earth 133 (or the lossy conducting medium 203). In the examples of FIGS. 9A and 9B, Z_wIs the characteristic impedance (in ohms), Z, of the elevated vertical feed line conductor 221_cIs the characteristic impedance (in ohms) of the coil 215, and Z_OIs the characteristic impedance of a vacuum.

At the base of the guided surface waveguide probe 200, the impedance seen in the "look up" configuration is Z_↑＝Z_Substrate. In the case of a load impedance of:

wherein C is_TIs a charge terminal T₁The impedance seen "looking up" into the vertical feed line conductor 221 (fig. 7) is given by:

and the impedance seen "looking up" into the coil 215 (fig. 7) is given by:

at the base of the guided surface waveguide probe 200, the impedance seen "looking down" to the lossy conducting medium 203 is Z_↓＝Z_inIt is derived from:

wherein Z_s＝0。

Ignoring losses, the equivalent image plane model may be tuned to Z at the physical boundary 136_↓+Z_↑Resonance when 0. Alternatively, in a low loss condition, X is at physical boundary 136_↓+X_↑Where X is the corresponding reactive component. Thus, the impedance at the real bulk boundary 136 when looking "up" into the guided surface waveguide probe 200 is the conjugate of the impedance at the real bulk boundary 136 when looking "down" into the lossy conducting medium 203. By adjusting the charge terminal T₁Is loaded with a load impedance Z_LWhile maintaining the traveling wave phase delay phi equal to the wave front tilt angle psi of the medium such that phi is phi, psi, fromWhile improving and/or maximizing coupling of the probe's electric field to the guided surface waveguide mode along the surface of the lossy conducting medium 203 (e.g., earth), the equivalent image plane model of fig. 9A and 9B can be tuned to resonate with respect to the image ground plane 139. In this way, the impedance of the equivalent composite image plane model is purely resistive, which maintains a superimposed standing wave on the probe structure, maximizing the voltage and the terminal T₁And the propagating surface wave is maximized by equations (1) - (3) and (16).

From the hankel solution, the guided surface wave excited by the guided surface waveguide probe 200 is an outwardly propagating traveling wave. At the charge terminal T of the guided surface waveguide probe 200 (FIGS. 3 and 7)₁The source distribution along the feed network 209 with the ground rod 218 is in fact structurally soundWave of travelAddingStanding waveAre superimposed. By positioning at a substantial height h_pAt or above the charge terminal T₁The phase delay of a traveling wave moving through the feed network 209 is matched to the wave front tilt angle associated with the lossy conducting medium 203. This mode matching allows the traveling wave to be launched along the lossy conducting medium 203. Once the phase delay has been established for the travelling wave, the charge terminal T₁Is loaded with a load impedance Z_LAdjusted to cause the probe structure to resonate in standing waves with respect to an image ground plane (130 of fig. 3 or 139 of fig. 8) at a composite depth of-d/2. In that case, the impedance seen from the image ground plane has zero reactance, and the charge terminal T₁The charge on is maximized.

the difference between the travelling wave phenomenon and the standing wave phenomenon is that (1) the travelling wave phase delay (θ ═ β d) on a transmission line segment of length d (sometimes referred to as a "delay line") is due to the propagation time delay, and (2) the position-dependent phase of the standing wave (which consists of a forward propagating wave and a backward propagating wave) depends on the line length propagation time delay at the interface between the line segments of different characteristic impedanceAndimpedance transformationBoth of them. In addition to the phase delay due to the physical length of the transmission line segment operating in a sinusoidal steady state, there is an additional reflection system that is subject to impedance discontinuitiesNumber phase, which is attributed to Z_oa/Z_obIn which Z is_oaAnd Z_obIs a characteristic impedance of two transmission line segments, such as, for example, a characteristic impedance Z_oa＝Z_cThe spiral coil section (fig. 9B) and the characteristic impedance Z_ob＝Z_wThe straight vertical feed line conductor segment (fig. 9B).

Due to this phenomenon, two relatively short transmission line segments with widely different characteristic impedances can be used to provide a large phase shift. For example, a probe structure consisting of two transmission line segments (one with low impedance and one with high impedance) that together total a physical length of 0.05 λ can be fabricated to provide a 90 ° phase shift equivalent to a 0.25 λ resonance. This is due to the large jump in characteristic impedance. In this way, a physically short probe structure may be electrically longer than the combined two physical lengths. This is illustrated in figures 9A and 9B, where the discontinuity in the impedance ratio provides a large jump in phase. The impedance discontinuity provides a substantial phase shift where the segments are joined together.

Referring to fig. 10, a flow chart 150 is shown illustrating an example of adjusting a guided surface waveguide probe 200 (fig. 3 and 7) to substantially mode-match a guided surface waveguide mode on a surface of a lossy conducting medium, the guided surface waveguide probe emitting a guided surface traveling wave along the surface of a lossy conducting medium 203 (fig. 3). Beginning with 153, the charge terminal T of the surface waveguide probe 200 is guided₁Is positioned at a defined height above the lossy conducting medium 203. Using the characteristics of the lossy conducting medium 203 and the operating frequency of the guided surface waveguide probe 200, the Hankel cross-over distance can also be determined by the magnitude of equations (20b) and (21) for-j γ ρ, and for R, as illustrated in FIG. 4_xAnd solving to obtain the product. The complex refractive index (n) can be determined using equation (41), and the complex Brewster angle (θ)_i,B) It may then be determined from equation (42). Charge terminal T₁Height (h) of_p) It may then be determined from equation (44). Charge terminal T₁Should be at physical height (h)_p) Or above the height of the entity in order to excite the far component of the hank function. Taking this height dependence into account initially when launching the surface waveIs described. To reduce or minimize the charge terminal T₁Has a height of the charge terminal T₁Is at least four times the spherical diameter (or equivalent spherical diameter).

At 156, charge terminal T is connected₁Increased charge Q on₁Is matched to the complex tilt angle psi. Phase delay (theta) of spiral coil_c) And/or phase delay (theta) of the vertical feed line conductor_y) Can be adjusted so that Φ equals the angle (Ψ) of the wave front tilt (W). Based on equation (31), the wavefront inclination angle (Ψ) may be determined from:

the electrical phase Φ may then be matched to the wavefront tilt angle. This angular (or phase) relationship is then considered when transmitting the surface wave. For example, the electrical phase delay Φ ═ θ_c+θ_yCan be adjusted by varying the geometric parameters of the coil 215 (fig. 7) and/or the length (or height) of the vertical feed line conductor 221 (fig. 7). By matching Φ ═ Ψ, the electric field can be established at the hankel crossover distance (R) at the boundary interface at a complex brewster angle_x) At or beyond the hankel crossing distance to excite the surface waveguide mode and launch a traveling wave along lossy conducting medium 203.

Next at 159, a charge terminal T₁Is tuned to resonate the equivalent image plane model of the guided surface waveguide probe 200. The depth (d/2) of the conductive image ground plane 139 (or 130 of fig. 3) of fig. 9A and 9B may be determined using equations (52), (53), and (54) and the value of the measurable lossy conductive medium 203 (e.g., earth). Using this depth, the phase shift (θ) between the ground plane 139 and the solid boundary 136 of the lossy conducting medium 203 is imaged_d) Theta may be used_d＝β_od/2. As seen "looking down" into the lossy conducting medium 203 (Z)_in) The decision may then be made using equation (65). This resonance relationship may be considered to maximize the transmitted surface wave.

Based on the adjusted parameters of the coil 215 and the length of the vertical feeding line conductor 221, the velocity factor, the phase delay, and the impedance of the coil 215 and the vertical feeding line conductor 221 may be determined using equations (45) through (51). In addition, a charge terminal T₁Self-capacitance (C)_T) the propagation factor (β) of coil 215 can be determined using, for example, equation (24)_p) the propagation phase constant (β) of the vertical feed line conductor 221 can be determined using equation (35) and is set_w) The determination may be made using equation (49). Using the self-capacitance and measurements of the coil 215 and the vertical feed line conductor 221, the impedance (Z) of the guided surface waveguide probe 200 as seen "looking up" into the coil 215_Substrate) The determination may be made using equations (62), (63), and (64).

The equivalent image plane model of the guided surface waveguide probe 200 can be tuned by adjusting the load impedance Z_LSo that Z is_SubstrateReactance component X of_SubstrateCounteracting Z_inReactance component X of_inOr X_Substrate+X_inResonate at 0. Thus, the impedance at the real bulk boundary 136 when looking "up" into the guided surface waveguide probe 200 is the conjugate of the impedance at the real bulk boundary 136 when looking "down" into the lossy conducting medium 203. Load impedance Z_LBy making the charge terminal T₁Capacitance (C)_T) Changing without changing the charge terminal T₁Electrical phase delay phi of theta_c+θ_yTo adjust. An iterative approach may be taken to tune the load impedance Z_LFor resonance of the equivalent image plane model with respect to the conductive image ground plane 139 (or 130). In this way, coupling of the electric field to the guided surface waveguide mode along the surface of the lossy conducting medium 203 (e.g., earth) may be improved and/or maximized.

This can be better understood by illustrating a scenario with numerical value examples. Consider a guided surface waveguide probe 200 that includes a physical height h_pTop-loaded vertical stubs of, and charge terminals T₁At the top, wherein the charge terminal T₁Operating frequency (f) of 1.85MHz via a helical coil and a vertical feed line conductor_o) To excite it.Using a height (H) of 16 feet₁) And has epsilon_rRelative permittivity and σ of 15₁A lossy conducting medium 203 (e.g., earth) with a conductivity of 0.010mhos/m, several plane wave propagation parameters may be for f_oCalculated at 1.850 MHz. Under these conditions, the Hankel crossing distance can be found to be R_x54.5 feet, with a solid height h_p5.5 feet, the solid height is entirely at the charge terminal T₁Below the actual height of the floor. Although H may have been used₁5.5 feet charge terminal height, but the higher probe structure reduces bound capacitance, allowing charge terminal T₁The larger percentage of free charges, thereby providing a larger field strength and excitation of the traveling wave.

The wavelength can be judged as:

where c is the speed of light. According to equation (41), the composite refractive index is:

where x is σ₁/ωε_oWhere ω is 2 π f_oAnd, according to equation (42), the composite brewster angle is:

using equation (66), the wavefront slope value can be determined as:

thus, the helical coil can be adjusted to match Φ Ψ 40.614 °

The velocity factor of a vertical feed line conductor (approximately a uniform cylindrical conductor with a diameter of 0.27 inches) can be given as V_w0.93. Because of h_p<<λ₀The propagation phase constant of the vertical feed line conductor can be approximated as:

according to equation (49), the phase delay of the vertical feed line conductor is:

θ_y＝β_wh_w≈β_wh_p＝11.640°。(72)

by adjusting the phase delay of the helical coil so that theta_c28.974 ° -40.614 ° -11.640 °, Φ would be equal to Ψ to match the guided surface waveguide mode. To illustrate the relationship between Φ and Ψ, fig. 11 shows a graph of both over a range of frequencies. Since both Φ and Ψ are frequency dependent, their respective curves can be seen to cross each other at approximately 1.85 MHz.

For a helical coil having a conductor diameter of 0.0881 inches, a coil diameter (D) of 30 inches, and a turn-to-turn spacing(s) of 4 inches, the velocity factor of the coil can be determined using equation (45):

and according to equation (35), the propagation factor is:

at theta_cIn the case of 28.974 °, the axial length (H) of the coil helix may be determined using equation (46) such that:

this height determines the position on the spiral coil where the vertical feed line conductor is connected, resulting in a coil with 8.818 turns (N ═ H/s).

The traveling wave phase delay at the coil and the vertical feeding line conductor is adjusted to match the wave plane tilt angle (phi-theta)_c+θ_yΨ), charge terminal T₁Load impedance (Z)_L) May be adjusted for guiding the standing wave resonance of the equivalent image plane model of the surface wave probe 200. Based on the measured permittivity, conductivity and permeability of the earth, the radial propagation constant can be determined using equation (57)

Furthermore, the composite depth of the conductive image ground plane can be approximated from equation (52) as:

wherein the corresponding phase shift between the conductive image ground plane and the physical boundary of the earth is derived by:

θ_d＝β_o(d/2)＝4.015-j4.73°。 (78)

using equation (65), "looking down" to the impedance seen in the lossy conducting medium 203 (i.e., earth) can be determined as:

Z_in＝Z_otanh(jθ_d)＝R_in+jX_in31.191+ j26.27 ohms. (79)

By directing a "look down" into the reactive component (X) seen in the lossy conducting medium 203_in) And "upwardsSee "the reactive component (X) seen in guided surface wave probe 200_Substrate) Matching, coupling in the guided waveguide modes can be maximized. This can be done by adjusting the charge terminal T₁Without changing the traveling wave phase delay of the coil and the vertical feed line conductor. For example, by adjusting the charge terminal capacitance (C)_T) To 61.8126pF, the load impedance is, according to equation (62):

and the reactive components at the boundary are matched.

Using equation (51), the impedance of the vertical feed line conductor (having a diameter (2a) of 0.27 inches) is given by

And the impedance seen "looking up" into the vertical feed line conductor is given by equation (63):

using equation (47), the characteristic impedance of the helical coil is given as

And the impedance seen "looking up" into the coil at the substrate is given by equation (64):

when compared to the solution of equation (79), it can be seen thatThe reactive components are opposite and approximately equal, and thus conjugate to each other. Thus, the impedance (Z) seen in the equivalent image plane model of FIGS. 9A and 9B is "seen up" from the ideal conductive image ground plane_ip) Only resistive or Z_ip＝R+j0。

When the electric field generated by the guided surface waveguide probe 200 (fig. 3) is established by matching the traveling wave phase delay of the feed network to the wave plane tilt angle and the probe structure resonates at a composite depth z-d/2 relative to the ideal conductive image ground plane, the field substantially mode-matches the guided surface waveguide mode on the surface of the lossy conducting medium along which the guided surface traveling wave is launched. As illustrated in FIG. 1, the guided field strength curve 103 of the guided electromagnetic field hasAnd exhibits a distinctive knee 109 on the log-log scale.

In summary, analytically and experimentally, the traveling wave component on the structure of the guided surface waveguide probe 200 has a phase delay (Φ) at the upper terminal of the guided surface waveguide probe that matches the wave surface tilt angle (Ψ) of the surface traveling wave (Φ ═ Ψ). In this condition, the surface waveguide may be considered to be "mode-matched". In addition, the resonant standing wave component on the structure of the guided surface waveguide probe 200 is guided at the charge terminal T₁Has a V_MAXAnd has a V below the image plane 139 (FIG. 8B)_MINWherein Z is at a composite depth of Z-d/2 and not at the junction at the solid boundary 136 (fig. 8B) of the lossy conducting medium 203_ip＝R_ip+ j 0. Finally, a charge terminal T₁With a sufficient height H of figure 3₁(h≥R_xtanψ_i,B) So that the electromagnetic wave incident on the lossy conducting medium 203 at the complex brewster angle is at a distance (≧ R)_x) Is realized as follows, whereinThe items are dominant. The receiving circuit can be connected with one or more guide surface waveguide probesTo facilitate wireless transmission and/or power delivery systems.

Referring back to fig. 3, the operation of guided surface waveguide probe 200 can be controlled to adjust for changes in operating conditions associated with guided surface waveguide probe 200. For example, the adaptive probe control system 230 may be used to control the feed network 209 and/or the charge terminal T₁To control the operation of the guided surface waveguide probe 200. The operating conditions may include, but are not limited to, the characteristics (e.g., conductivity σ and relative permittivity ε) of the lossy conducting medium 203_r) Variations in field strength, and/or variations in loading of the guided surface waveguide probe 200. As can be seen from equations (31), (41) and (42), the refractive index (n), the composite Brewster angle (θ)_i,B) And wave surface inclination (| W | e)^jΨ) May be affected by changes in the conductivity and permittivity of the soil caused by, for example, weather conditions.

Devices such as, for example, conductivity measurement probes, permittivity sensors, surface parameter meters, field strength meters, current monitors, and/or load receivers may be used to monitor changes in operating conditions and provide information regarding the current operating conditions to the adaptive probe control system 230. The probe control system 230 may then make one or more adjustments to the guided surface waveguide probe 200 to maintain the specified operating conditions for the guided surface waveguide probe 200. For example, as humidity and temperature change, the conductivity of the soil also changes. Conductivity measurement probes and/or permittivity sensors may be located at various locations around the guided surface waveguide probe 200. In general, it is intended to monitor the Hankel crossing distance R for the operating frequency_xAt or about the hank crossing distance R_xElectrical conductivity and/or permittivity. The conductivity measurement probe and/or the permittivity sensor may be located at multiple locations (e.g., in each quadrant) around the guided surface waveguide probe 200.

The conductivity measurement probe and/or the permittivity sensor may be configured to periodically assess conductivity and/or permittivity and communicate information to the probe control system 230. Information may be communicated to probe control system 230 via a network, such as, but not limited to, a LAN, WLAN, cellular network, or other suitable wired or wirelessA wire communication network. Based on the monitored conductivity and/or permittivity, the probe control system 230 can evaluate the refractive index (n), the composite brewster angle (θ)_i,B) And/or wave surface tilt (| W | e)^jΨ) And adjusting the guided surface waveguide probe 200 to maintain the phase delay (Φ) of the feed network 209 equal to the wavefront tilt angle (Ψ) and/or to maintain the resonance of the equivalent imageplane model of the guided surface waveguide probe 200. This can be done by adjusting, for example, θ_y、θ_cAnd/or C_TTo complete. For example, the probe control system 230 may adjust the charge terminal T₁And/or to the charge terminal T₁Phase delay (theta) of_y,θ_c) To maintain the electrical emission efficiency of the guided surface wave at or near its maximum. For example, a charge terminal T₁Can be varied by changing the size of the terminals. The charge distribution can also be increased by increasing the charge terminal T₁So that the self-charge terminal T can be reduced₁The chance of discharge. In other embodiments, the charge terminal T₁May include a variable impedance Z that can be adjusted to vary the load impedance_LThe variable inductance of (1). Applied to the charge terminal T₁May be adjusted by varying the tap position on the coil 215 (fig. 7) and/or by including a plurality of predefined taps along the coil 215 and switching between different predefined tap positions to maximize transmission efficiency.

A Field Strength (FS) meter may also be distributed near the guided surface waveguide probe 200 to measure the field strength of the field associated with the guided surface wave. The field or FS meter may be configured to detect field strength and/or changes in field strength (e.g., electric field strength) and communicate information to the probe control system 230. Information may be communicated to the probe control system 230 via a network, such as, but not limited to, a LAN, WLAN, cellular network, or other suitable communication network. As the load and/or environmental conditions change or change during operation, the guided surface waveguide probe 200 can be adjusted to maintain a specified field strength at the FS meter location in order to ensure proper power transfer to the receivers and the loads supplied by those receivers.

For example, toCharge terminal T₁Phase delay (phi ═ theta)_y+θ_c) May be adjusted to match the wavefront tilt angle (Ψ). By adjusting one or both phase delays, the guided surface waveguide probe 200 can be adjusted to ensure a wave surface tilt corresponding to the composite brewster angle. This can be done by adjusting the tap position on coil 215 (fig. 7) to change the supply to charge terminal T₁Is delayed. Is supplied to the charge terminal T₁May also be increased or decreased to adjust the electric field strength. This can be done by adjusting the output voltage of the excitation source 212 or by adjusting or resetting the feed network 209. For example, the position of tap 227 (fig. 7) for AC source 212 may be adjusted to increase charge terminal T₁The voltage seen. Maintaining the field strength level within the predefined range may improve coupling through the receiver, reduce ground current losses and avoid interfering with transmissions from other guided surface waveguide probes 200.

The probe control system 230 may be implemented using hardware, firmware, software executed by hardware, or a combination thereof. For example, the probe control system 230 may include processing circuitry including a processor and a memory, both of which may be coupled to a local interface, such as, for example, a data bus with accompanying control/address buses, as will be appreciated by one of ordinary skill. A probe control application may be executed by the processor to adjust the operation of the guided surface waveguide probe 200 based on the monitored conditions. The probe control system 230 may also include one or more network interfaces for communicating with various monitoring devices. Communication may be accomplished via a network such as, but not limited to, a LAN, WLAN, cellular network, or other suitable communication network. The probe control system 230 may include, for example, a computer system such as a server, desktop computer, laptop computer, or other system with similar capabilities.

Referring back to the example of FIG. 5A, compound angle trigonometry is shown for charge terminal T₁In the Hankel crossing distance (R)_x) Has a composite Brewster angle (theta)_i,B) Is used for the ray optical interpretation of the incident electric field (E). Recall that for lossy conducting media, BruThe stirling angle is complex and specified by equation (38). Electrically, the geometric parameter being determined by the charge terminal T₁Electrical effective height (h) of_eff) The correlation is given by equation (39). Because of the physical height (h)_p) And the Hankel crossing distance (R)_x) All are actual quantities, so the cross distance (W) in Hankel is_Rx) The desired angle of inclination of the guide surface wave is equal to the composite effective height (h)_eff) Phase (Φ). At the charge terminal T₁Positioned at a substantial height h_pAnd excited with charges having the appropriate phase Φ, the resulting electric field crosses at a distance R of Hankel_xUsing a lossy conducting medium boundary and incident at a brewster angle. Under these conditions, guided surface waveguide modes can be excited with no or substantially negligible reflection.

However, equation (39) means that the physical height of the guided surface waveguide probe 200 can be relatively small. Although this will excite the guided surface waveguide mode, it may result in an excessively large bound charge with little free charge. For compensation, the charge terminal T₁May be raised to an appropriate level to increase the amount of free charge. As an exemplary rule of thumb, the charge terminal T₁Can be positioned at the charge terminal T₁Is about 4-5 times (or more) the effective diameter of (a). FIG. 6 illustrates the charge terminal T₁Increasing to the physical height (h) shown in FIG. 5A_p) The effect of the above. The increased elevation causes the wavefront to tilt the lossy conducting medium a distance that is moved beyond the hankel intersection 121 (fig. 5A). To improve coupling in guided surface waveguide modes and thus provide greater launch efficiency of guided surface waves, the lower compensation terminal T₂Can be used for adjusting the charge terminal T₁Total effective height (h)_TE) So that the slope of the wave surface at the hankel crossing distance is at the brewster angle.

Referring to FIG. 12, an example of a guided surface waveguide probe 200c is shown that includes a raised charge terminal T₁And a lower compensation terminal T₂The terminals are arranged along a vertical axis z, which is normal to the plane provided by the lossy conducting medium 203. In this regardIn other words, the charge terminal T₁Is directly placed at the compensating terminal T₂Above, although it is possible to use two or more charge and/or compensation terminals T_NSome other arrangement of (2). According to an embodiment of the present disclosure, a guided surface waveguide probe 200c is disposed over a lossy conducting medium 203. The lossy conducting medium 203 constitutes region 1 and the second medium 206 constitutes region 2, which shares a boundary interface with the lossy conducting medium 203.

Guided surface waveguide probe 200c includes a feed network 209 that couples an excitation source 212 to a charge terminal T₁And a compensation terminal T₂. According to various embodiments, the charge Q₁And Q₂Can be applied to respective charge terminals T₁And a compensation terminal T₂Depending on the application to the terminal T at any given instant₁And T₂The voltage of (c). I is₁For feeding charge terminals T via terminal leads₁Charge Q on₁Is conducting current, and I₂For feeding the compensating terminal T via the terminal lead₂Charge Q on₂Is conducted.

According to the embodiment of fig. 12, the charge terminal T₁Is a physical height H positioned above the lossy conducting medium 203₁And compensate terminal T₂Is positioned directly at T along the vertical axis z₁Lower solid height H₂Of (a) H₂Is less than H₁. The height H of the transmission structure may be calculated as H ═ H₁-H₂. Charge terminal T₁With isolated (or self-) capacitance C₁And compensating terminal T₂With isolated (or self-) capacitance C₂. Mutual capacitance C_MCan also be at the terminal T₁And terminal T₂Depending on the distance between the terminals. During operation, the charge Q₁And Q₂Are respectively applied to the charge terminals T₁And a compensation terminal T₂Depending on the application to the charge terminal T at any given instant₁And a compensation terminal T₂The voltage of (c).

Referring next to FIG. 13, there is shown electricity passing through FIG. 12Load terminal T₁Increased charge Q on₁And a compensation terminal T₂Ray-optical interpretation of the resulting effect. At the charge terminal T₁The compensation terminal T is raised to a height where the rays intersect the lossy conducting medium at a brewster angle (as illustrated by line 163) at a distance greater than the hank crossing point 121₂Can be used to adjust h by compensating for increased height_TE. Compensation terminal T₂The effect of (a) is to reduce the electrically effective height of the guided surface waveguide probe (or effectively increase the lossy media interface) so that the wave plane tilt at the hankel crossing distance is at the brewster angle, as illustrated by line 166.

The total effective height can be written as the charge terminal T₁Associated upper effective height (h)_UE) And a compensation terminal T₂Associated lower effective height (h)_LE) So that to be superimposed on each other, such that

Wherein phi_UFor applying to the upper charge terminal T₁Phase delay of phi_LFor applying to the lower compensation terminal T₂phase retardation of, β ═ 2 π/λ_pIs the propagation factor, h, from equation (35)_pIs a charge terminal T₁And h is a physical height of_dFor compensating the terminal T₂The physical height of (a). If additional lead length is considered, the lead length can be passed to the charge terminal T₁Height h of the body_pIncreasing charge terminal lead length z and compensating terminal T₂Height h of the body_dThe increase in the compensation terminal lead length y is explained as follows

The lower effective height can be used to adjust the total effective height (h)_TE) To equal the composite effective height (h) of fig. 5A_eff)。

Equation (85) or (86) can be used to determine the compensation terminal T₂The physical height and phase angle of the lower puck to feed the terminals in order to obtain the desired wave front tilt at the hankel crossing distance. For example, equation (86) may be rewritten as applied to charge terminal T₁Is compensated with the terminal height (h)_d) Is varied to obtain

To determine the compensation terminal T₂The relationships discussed above may be utilized for positioning. First, the total effective height (h)_TE) To the upper charge terminal T₁Composite effective height (h)_UE) And a lower compensation terminal T₂Composite effective height (h)_LE) As represented in equation (86). The tangent to the angle of incidence can then be represented geometrically as

Which is equal to the definition of the wave front tilt W. Finally, given a desired Hankel crossing distance R_x，h_TECan be adjusted so that the wave front tilt of the incident ray matches the composite brewster angle at the hankel intersection 121. This can be done by adjusting h_p、Φ_UAnd/or h_dTo complete.

This concept may be better understood when discussed in the context of an example of a guided surface waveguide probe. Referring to FIG. 14, a diagrammatic representation of an example of a guided surface waveguide probe 200d is shown that includes an upper charge terminal T₁(e.g., height h)_TSphere of) and lower compensation terminal T₂(e.g., at height h)_dA circular disk) positioned along a vertical axis z that is substantially normal to a plane provided through the lossy conducting medium 203. During operation, the charge Q₁And Q₂Are respectively applied to the charge terminals T₁And a compensation terminal T₂Depending on the application to the terminal T at any given instant₁And T₂The voltage of (c).

AC source 212 acts as a charge terminal T₁Coupled to the guided surface waveguide probe 200d via a feed network 209 that includes a coil 215, such as, for example, a helical coil. The AC source 212 may cross the lower portion of the coil 215 via a tap 227, as shown in fig. 14, or may be inductively coupled to the coil 215 via a primary coil. The coil 215 may be coupled to the ground bar 218 at a first end and to the charge terminal T at a second end₁. In some embodiments, and charge terminal T₁May be adjusted using a tap 224 at the second end of the coil 215. Compensation terminal T₂Positioned above and substantially parallel to a lossy conducting medium 203, such as ground or earth, and excited via taps 233 coupled to coils 215. An ammeter 236 located between the coil 215 and the ground rod 218 may be used to provide current (I) at the base of the guided surface waveguide probe₀) An indication of the magnitude of (d). Alternatively, a current clamp may be used around the conductor coupled to the ground rod 218 to obtain the pair current (I)₀) An indication of the magnitude of (d).

In the example of fig. 14, the coil 215 is coupled at a first end to a ground bar 218 and at a second end to a charge terminal T via a vertical feed line conductor 221₁. In some embodiments, and charge terminal T₁May be adjusted using a tap 224 at the second end of the coil 215 as shown in fig. 14. The coil 215 may be excited at an operating frequency by the AC source 212 via a tap 227 at a lower portion of the coil 215. In other embodiments, the AC source 212 may be inductively coupled to the coil 215 via a primary coil. Compensation terminal T₂Via a tap 233 coupled to the coil 215. An ammeter 236 located between the coil 215 and the ground rod 218 can be used to provide an indication of the magnitude of the current at the base of the guided surface waveguide probe 200 d. Alternatively, can be coupled aroundThe conductors of the ground rod 218 use current clamps to obtain an indication of the magnitude of the current. Compensation terminal T₂Is positioned above and substantially parallel to a lossy conducting medium 203, such as ground.

In the example of fig. 14, with the charge terminal T located on the coil 215₁Is used for compensating the terminal T₂Above the connection point of tap 233. Such adjustment allows for increased voltage (and thus higher charge Q)₁) Is applied to the upper charge terminal T₁. In other embodiments, for the charge terminal T₁And a compensation terminal T₂May be reversed. It is possible to adjust the total effective height (h) of the guided surface waveguide probe 200d_TE) To excite at a Hankel crossing distance R_xWith an electric field that guides the slope of the surface wave. The hankel cross-distance may also be equalized for R by equalizing the magnitudes of equations (20b) and (21) for-j γ ρ_xSolved, as illustrated in fig. 4. Refractive index (n), complex Brewster angle (θ)_i,BAnd psi_i,B) Wave front tilt (| W | e)^jΨ) And a composite effective height (h)_eff＝h_pe^jΦ) The determination may be as described with respect to equations (41) - (44) above.

Using selected charge terminals T₁In this configuration, the spherical diameter (or effective spherical diameter) can be determined. For example, if the charge terminal T₁Rather than being arranged as a sphere, the terminal configuration can be modeled as a spherical capacitor having an effective spherical diameter. Charge terminal T₁Can be selected to provide a sufficiently large surface for the charge Q₁Is applied to the terminal. In general, the charge terminal T is intended to be₁Made as large as practical. Charge terminal T₁Should be large enough to avoid ionization of the surrounding air, which could lead to electrical discharge or sparking around the charge terminals. To reduce the charge terminal T₁The amount of bound charge on the charge terminal T₁The desired elevation above which free charge is provided for launching guided surface waves should be at least 4-5 times the effective spherical diameter above the lossy conducting medium (e.g., earth). Compensation terminal T₂Can be used to adjust the total effective height (h) of the guided surface waveguide probe 200d_TE) To excite at R_xWith an electric field that guides the slope of the surface wave. Compensation terminal T₂Can be positioned at the charge terminal T₁Lower h_d＝h_T-h_pWhere h is_TIs a charge terminal T₁Total physical height of (a). At the compensating terminal T₂Is installed in position and phase delayed by phi_UIs applied to the upper charge terminal T₁Is applied to the lower compensation terminal T₂Is delayed by phi_LThe relationship of equation (86) may be used to determine such that:

in an alternative embodiment, the compensation terminal T₂Can be positioned at a height h_dWhere Im { Φ }_L0. This is illustrated graphically in FIG. 15A, which shows Φ respectively_UGraphs 172 and 175 of the imaginary and real parts. Compensation terminal T₂Is positioned at a height h_dWhere Im { Φ }_U0 as graphically illustrated in graph 172. At this fixed height, the coil phase Φ_UCan be selected from Re { phi_UJudgments, as graphically illustrated in graph 175.

With the AC source 212 coupled to the coil 215 (e.g., at a 50 Ω point to maximize coupling), the position of the tap 233 may be adjusted for compensating the terminal T at the operating frequency₂Resonating in parallel with at least a portion of the coil. FIG. 15B shows a schematic view of the universal electrical wiring diagram (hookup) of FIG. 14, wherein V₁Is a voltage, V, applied from the AC source 212 to the lower portion of the coil 215 via tap 227₂Is the voltage at tap 224, which is supplied to the upper charge terminal T₁And V is₃For being applied to the lower compensation terminal T through the tap 233₂The voltage of (c). Resistance R_pAnd R_dRespectively represent charge terminals T₁And a compensation terminal T₂Ground loop resistance. Charge terminal T₁And compensationTerminal T₂May be configured as a sphere, cylinder, toroid, ring, cage, or any other combination of capacitive structures. Charge terminal T₁And a compensation terminal T₂Can be selected to provide a sufficiently large surface for the charge Q₁And Q₂Is applied to the terminal. In general, the charge terminal T is intended to be₁Made as large as practical. Charge terminal T₁Should be large enough to avoid ionization of the surrounding air, which could lead to electrical discharge or sparking around the charge terminals. Charge terminal T₁And a compensation terminal T₂Self-capacitance C_pAnd C_dThe determination can be made using, for example, equation (24), respectively.

As can be seen in FIG. 15B, the resonant circuit is compensated for terminal T through at least a portion of the inductance of coil 215₂Self-capacitance C_dAnd a compensation terminal T₂Associated ground loop resistance R_dAnd (4) forming. The parallel resonance can be adjusted and applied to the compensation terminal T₂Voltage V of₃(e.g. by adjusting the tap 233 position on coil 215) or by adjusting the compensation terminal T₂To adjust C by height and/or size_dTo be established. The position of the coil taps 233 may be adjusted for parallel resonance, generating a ground current through the ground rod 218 and through the ammeter 236 to a maximum point. At the established compensation terminal T₂After the parallel resonance, the position of the tap 227 for the AC source 212 may be adjusted to the 50 Ω point on the coil 215.

Voltage V from coil 215₂Can be applied to the charge terminal T₁And the position of the tap 224 may be adjusted such that the total effective height (h)_TE) Is approximately equal to the hankel crossing distance (R)_x) To guide the surface wave inclination (W)_Rx) The angle of (c). The position of the coil tap 224 may be adjusted until this operating point is reached, producing a ground current through the ammeter 236, increasing to a maximum value. At this point, the resulting field excited by the guided surface waveguide probe 200d is substantially mode-matched to the guided surface waveguide mode on the surface of the lossy conducting medium 203, thereby generatingGuiding the emission of surface waves along the surface of the lossy conducting medium 203. This can be verified by measuring the field strength along a radial line extending from the guided surface waveguide probe 200.

Comprising a compensation terminal T₂Can follow the resonance of the charge terminal T₁And/or applied to the charge terminal T via the tap 224₁The adjustment of the voltage of (c) is changed. Although adjusting the compensation terminal circuit for resonance assists in the subsequent adjustment of the charge terminal connections, it is necessary to adjust the cross-over distance (R) in the Hankel range_x) To establish a guided surface wave tilt (W)_Rx). The system may be further adapted to improve coupling by: the position of tap 227 for AC source 212 is iteratively adjusted to be at the 50 Ω point on coil 215 and the position of tap 233 is adjusted to maximize the ground current through ammeter 236. Comprising a compensation terminal T₂The resonance of the circuit of (a) may shift when the position of taps 227 and 233 is adjusted or when other components are attached to the coil 215.

In other embodiments, the voltage V from the coil 215₂Can be applied to the charge terminal T₁And the position of the tap 233 may be adjusted so that the total effective height (h)_TE) Is approximately equal to R_xAt the angle of inclination (Ψ) of the guided surface wave. The position of the coil taps 224 may be adjusted until an operating point is reached, producing a ground current through the ammeter 236, substantially to a maximum value. The resulting field is substantially mode-matched to the guided surface wave mode on the surface of lossy conducting medium 203 and the guided surface wave is emitted along the surface of lossy conducting medium 203. This can be verified by measuring the field strength along a radial line extending from the guided surface waveguide probe 200. The system may be further adapted to improve coupling by: the position of tap 227 for AC source 212 is iteratively adjusted to be at the 50 Ω point on coil 215 and the positions of taps 224 and/or 233 are adjusted to maximize the ground current through ammeter 236.

Referring back to fig. 12, the operation of guided surface waveguide probe 200 can be controlled to adjust for variations in operating conditions associated with guided surface waveguide probe 200. For exampleThe probe control system 230 may be used to control the feed network 209 and/or the charge terminal T₁And/or compensation terminal T₂To control the operation of the guided surface waveguide probe 200. The operating conditions may include, but are not limited to, the characteristics (e.g., conductivity σ and relative permittivity ε) of the lossy conducting medium 203_r) Variations in field strength, and/or variations in loading of the guided surface waveguide probe 200. As can be seen from equations (41) - (44), the refractive index (n), the composite Brewster angle (θ)_i,BAnd psi_i,B) Wave front tilt (| W | e)^jΨ) And a composite effective height (h)_eff＝h_pe^jΦ) May be affected by changes in the conductivity and permittivity of the soil caused by, for example, weather conditions.

Devices such as, for example, conductivity measurement probes, permittivity sensors, surface parameter meters, field strength meters, current monitors, and/or load receivers may be used to monitor changes in operating conditions and provide information regarding the current operating conditions to probe control system 230. The probe control system 230 may then make one or more adjustments to the guided surface waveguide probe 200 to maintain the specified operating conditions for the guided surface waveguide probe 200. For example, as humidity and temperature change, the conductivity of the soil also changes. Conductivity measurement probes and/or permittivity sensors may be located at various locations around the guided surface waveguide probe 200. In general, it is intended to monitor the Hankel crossing distance R for the operating frequency_xAt or about the hank crossing distance R_xElectrical conductivity and/or permittivity. The conductivity measurement probe and/or the permittivity sensor may be located at multiple locations (e.g., in each quadrant) around the guided surface waveguide probe 200.

Referring next to FIG. 16, an example of a guided surface waveguide probe 200e is shown that includes a charge terminal T₁And a charge terminal T₂The terminals being arranged along a vertical axis z. A guided surface waveguide probe 200e is disposed over lossy conducting medium 203, forming region 1. In addition, the second medium 206 shares a boundary interface with the lossy conducting medium 203 and constitutes the region 2. Charge terminal T₁And T₂Is positioned over the lossy conducting medium 203.Charge terminal T₁Is positioned at a height H₁And a charge terminal T₂Directly positioned at T along a vertical axis z₁Height H of the lower part₂Wherein H is₂Is less than H₁. The height H of the transmission structure provided by the guide surface waveguide probe 200e is H ═ H₁-H₂. Guided surface waveguide probe 200e includes a feed network 209 that couples an excitation source 212 to a charge terminal T₁And T₂。

Charge terminal T₁And/or T₂Includes a conductive substance that can hold a charge that can be sized to hold as much charge as is practically possible. Charge terminal T₁With self-capacitance C₁And a charge terminal T₂With self-capacitance C₂The self-capacitance may be determined using, for example, equation (24). Through the charge terminal T₁At the charge terminal T₂Placed directly above, at the charge terminal T₁And T₂Mutual capacitance C is generated between them_M. Note that the charge terminal T₁And T₂Need not be equal, but each may have a separate size and shape and may comprise different conductive materials. Finally, the field strength of the guided surface wave emitted by the guided surface waveguide probe 200e and the terminal T₁The amount of charge on is proportional. Electric charge Q₁Then with the self-capacitance C₁In proportion to the self-capacitance and the charge terminal T₁Is related because of Q₁＝C₁V, where V is applied to the charge terminal T₁The voltage of (c).

Guided surface waveguide probe 200e, when properly tuned for operation at a predefined operating frequency, generates a guided surface wave along the surface of lossy conducting medium 203. The excitation source 212 may generate electrical energy at a predefined frequency that is applied to the guided surface waveguide probe 200e to excite the structure. When the electromagnetic field generated by the guided surface waveguide probe 200e is substantially mode-matched to the lossy conducting medium 203, the electromagnetic field is substantially synthesized into a wave front incident at a complex brewster angle, resulting in little or no reflection. Therefore, the surface waveguide probe 200e does not generate a radiation wave, but emits a guided surface traveling wave along the surface of the lossy conducting medium 203. Energy from excitation source 212 may be transmitted as a zenith surface current to one or more receivers located within the effective transmission range of guided surface waveguide probe 200 e.

Determinable lossy conducting medium 203 surface radial anechoic surface current J_ρThe asymptote of (rho) is close to J₁(p) and distance J₂(p) wherein

Is close to (rho)<λ/8)：

Distance (p)>>λ/8)：

Wherein I₁For feeding a first charge terminal T₁Charge Q on₁Is conducting current, and I₂For feeding the second charge terminal T₂Charge Q on₂Is conducted. Upper charge terminal T₁Charge Q on₁By Q₁＝C₁V₁Is determined, wherein C₁Is a charge terminal T₁The isolated capacitance of (2). Note that there are groups as set forth aboveDerived J₁Is derived from the Leontovich boundary condition and is the first charge terminal Q₁The quasi-static field of the rising oscillating charge on the surface of the dielectric medium 203. Quantity Z_ρ＝jωμ_o/γ_eIn order to lose the radial impedance of the conductive medium, where gamma_e＝(jωμ₁σ₁-ω²μ₁ε₁)^1/2。

Representing near radial current and far radial current as set forth in equations (90) and (91)The asymptotes of the flow are complex quantities. According to various embodiments, the solid surface current J (ρ) is synthesized to match the current asymptote as closely as possible in magnitude and phase. In other words, close to, | J (ρ) | is intended to be | J₁Is a tangent of, and away from, | J (ρ) | is intended to be | J₂Tangent of l. Further, according to various embodiments, the phase of J (ρ) will be from near J₁To shift away from J₂The phase of (c).

To match guided surface wave modes at the transmission site to launch guided surface waves, far away from surface current | J₂The phase of | will be related to the near surface current | J₁The phase difference of | corresponds to e^{-jβ(ρ2-ρ1)}Plus a constant of approximately 45 degrees or 225 degrees. This is becauseThere are two roots, one near π/4 and one near 5 π/4. Properly adjusted composite radial surface current of

Note that this is consistent with equation (17). This J (p) surface current automatically generates a field by the Markesler equation, which conforms to

Thus, the off-surface current | J for the matched guided surface wave mode₂And near surface current | J₁The phases between |)The bit difference is a characteristic attributed to the hankel functions in equations (93) - (95), which are consistent with equations (1) - (3). It is important to recognize that the fields represented by equations (1) - (6) and (17) and equations (92) - (95) have the property of transmission line mode shape coupling to the lossy interface rather than the radiated field associated with ground wave propagation.

To obtain the appropriate voltage magnitude and phase for a given design of the guided surface waveguide probe 200e at a given location, an iterative approach may be used. Specifically, the terminal T may be considered to be directed to₁And T₂Feeding current, charge terminal T₁And T₂The charge on and its image in the lossy conducting medium 203 is used to perform an analysis of a given excitation and configuration of the guided surface waveguide probe 200e in order to determine the resulting radial surface current density. This process may be repeated until the optimal configuration and excitation for a given guided surface waveguide probe 200e is determined based on the desired parameters. To assist in determining whether or not the guided surface waveguide probe 200e is operating at an optimal level, the guided field strength curve 103 (FIG. 1) may be based on the conductivity (σ) of region 1 at the location of the guided surface waveguide probe 200e using equations (1) - (12)₁) And permittivity (. epsilon.) of region 1₁) Is generated. This guided field strength curve 103 may provide a reference for operation such that the measured field strength may be compared to the magnitude indicated by the guided field strength curve 103 in order to determine whether an optimal transmission has been achieved.

To achieve the optimal conditions, various parameters associated with the guided surface waveguide probe 200e may be adjusted. One parameter that may be varied to adjust the guided surface waveguide probe 200e is the charge terminal T₁And/or T₂Relative to the height of the surface of the lossy conducting medium 203. In addition, the charge terminal T can also be adjusted₁And T₂The distance or spacing therebetween. In doing so, the charge terminal T may be minimized or otherwise altered₁And T₂Mutual capacitance C with the lossy conducting medium 203_MOr any bound capacitance, as would be appreciated. The respective charge terminals T can also be adjusted₁And/or T₂The size of (2). By changing the charge terminal T₁And/orT₂Will change the respective self-capacitance C₁And/or C₂And mutual capacitance C_MAs can be appreciated.

Additionally, another parameter that may be adjusted is the feed network 209 associated with the guided surface waveguide probe 200 e. This may be accomplished by adjusting the magnitude of the inductive reactance and/or capacitive reactance that make up the feed network 209. For example, where the inductive reactance comprises a coil, the number of turns on such coil may be adjusted. Finally, adjustments to the feed network 209 may be made to change the electrical length of the feed network 209, thereby affecting the charge terminal T₁And T₂Magnitude and phase of the voltage on.

Note that the iterative transfer by making various adjustments may be carried out by using a computer model or by adjusting the physical structure (as may be appreciated). By making the above adjustments, a corresponding "near" surface current J can be generated₁And "keep away" surface current J₂These surface currents are approximately the same current J (ρ) for the guided surface wave modes specified in equations (90) and (91) set forth above. In doing so, the resulting electromagnetic field will be substantially or substantially mode-matched to the guided surface wave mode on the surface of the lossy conducting medium 203.

Although not shown in the example of fig. 16, operation of the guided surface waveguide probe 200e may be controlled to adjust for variations in operating conditions associated with the guided surface waveguide probe 200. For example, the probe control system 230 shown in FIG. 12 may be used to control the feed network 209 and/or the charge terminal T₁And/or T₂To control the operation of the guided surface waveguide probe 200 e. The operating conditions may include, but are not limited to, the characteristics (e.g., conductivity σ and relative permittivity ε) of the lossy conducting medium 203_r) Variations in field strength, and/or variations in loading of the guided surface waveguide probe 200 e.

Referring now to FIG. 17, an example of the guided surface waveguide probe 200e of FIG. 16 is shown, herein denoted as guided surface waveguide probe 200 f. Guided surface waveguide probe 200f includes a charge terminal T₁And T₂The charge terminals are positioned along a vertical axis z that is substantially normal to a plane provided through the lossy conducting medium 203 (e.g., the earth). A second medium 206 is over the lossy conducting medium 203. Charge terminal T₁With self-capacitance C₁And a charge terminal T₂With self-capacitance C₂. During operation, the charge Q₁And Q₂Are respectively applied to the charge terminals T₁And T₂Dependent on application to the charge terminal T at any given instant₁And T₂The voltage of (c). Mutual capacitance C_MMay be present at the charge terminal T₁And T₂Depending on the distance between these charge terminals. In addition, bound capacitances may be present at the respective charge terminals T₁And T₂And a lossy conducting medium 203, depending on the respective charge terminal T₁And T₂Relative to the height of the lossy conducting medium 203.

Guided surface waveguide probe 200f includes a feed network 209 that includes an inductive impedance comprising a coil L having a pair of leads_1aThe pair of leads are coupled to a charge terminal T₁And T₂Each of which is described above. In one embodiment, coil L_1aIs designated as having an electrical length that is one-half (1/2) of the wavelength at the operating frequency of the guided surface waveguide probe 200 f.

Although the coil L_1aIs designated as approximately one-half (1/2) of the wavelength at the operating frequency, but it is understood that the coil L is_1aCan be specified to have electrical lengths at other values. According to one embodiment, the coil L_1aThe fact of having an electrical length of approximately one-half of a wavelength at the operating frequency provides advantages in that: at the charge terminal T₁And T₂Which produces the maximum voltage difference. Nevertheless, the coil L_1aMay be increased or decreased when the guided surface waveguide probe 200f is adjusted to obtain optimal excitation of the guided surface wave mode. The length of the coil may be adjusted by means of a slit at one or both ends of the coilA joint is provided. In other embodiments, the possible conditions are: the inductive impedance is specified as having an electrical length that is significantly less than or greater than 1/2 of the wavelength at the operating frequency of the guided surface waveguide probe 200 f.

Excitation source 212 may be coupled to feed network 209 via magnetic coupling. Specifically, the excitation source 212 is coupled to the coil L_PThe coil is inductively coupled to the coil L_1a. This may be done by chain coupling, tapped coils, variable reactance, or other coupling methods as may be appreciated. For this purpose, the coil L_PActing as a primary coil, and a coil L_1aActing as a secondary coil, as can be appreciated. To adjust the guided surface waveguide probe 200f to achieve desired guided surface wave transmission, the respective charge terminals T₁And T₂May vary in height relative to the lossy conducting medium 203 and to each other. In addition, the charge terminal T can be changed₁And T₂The size of (2). In addition, a coil L_1aCan be made by adding or eliminating a plurality of turns or by changing the coil L_1aAnd some other dimensions. Coil L_1aOne or more taps for adjusting the electrical length may also be included, as shown in fig. 17. Can also be adjustably connected to the charge terminal T₁Or T₂The position of the tap of either.

Referring next to fig. 18A, 18B, 18C, and 19, an example of a generalized receive circuit for using guided surface waves in a wireless power delivery system is shown. Fig. 18A and 18B-18C include a linear probe 303 and a tuned resonator 306, respectively. Figure 19 is a magnetic coil 309 according to various embodiments of the present disclosure. According to various embodiments, each of the linear probe 303, the tuned resonator 306, and the magnetic coil 309 may be used to receive power transmitted in the form of a guided surface wave on the surface of the lossy conducting medium 203 according to various embodiments. As mentioned above, in one embodiment, the lossy conducting medium 203 comprises a terrestrial medium (or earth).

With specific reference to fig. 18A, the open end voltage at the output terminal 312 of the linear probe 303 depends on the effective height of the linear probe 303. For this reason, the endpoint voltage can be calculated as

Wherein E_incIs the intensity of the incident electric field (in volts/meter) induced on the linear probe 303, dl is the integral component in the direction of the linear probe 303, and h_eIs the effective height of the linear probe 303. An electrical load 315 is coupled to the output terminal 312 via an impedance matching network 318.

When the linear probe 303 is subjected to a guided surface wave as described above, a voltage is generated across the output terminal 312, which can be applied to the electrical load 315 via the conjugate impedance matching network 318, as the case may be. To facilitate power flow to the electrical load 315, the electrical load 315 should be substantially impedance matched to the linear probe 303, as will be described below.

Referring to fig. 18B, the ground current exciting coil 306a having a phase shift equal to the wave surface tilt of the guided surface wave includes a charge terminal T_RThe charge terminal is raised (or suspended) above the lossy conducting medium 203. Charge terminal T_RWith self-capacitance C_R. Alternatively, the charge terminal T may be provided_RA bound capacitance (not shown) exists between the lossy conducting medium 203 and the charge terminal T over the lossy conducting medium 203_ROf (c) is measured. The bound capacitance will preferably be minimized as much as practicable, although this may not be entirely necessary in every case.

The tuned resonator 306a also includes a receiver network including a coil L with a phase shift Φ_R. Coil L_RIs coupled to the charge terminal T_RAnd a coil L_RAnd at the other end to a lossy conducting medium 203. The receiver network may include a vertical supply line conductor that connects the coil L_RCoupled to the charge terminal T_R. For this purpose, the coil L_R(which may also be referred to as a tuning resonator L)_R-C_R) Comprises a stringCoupled resonator due to charge terminal C_RAnd a coil L_RAre positioned in series. Coil L_RCan be controlled by changing the charge terminal T_RAnd/or height of and/or adjustment of the coil L_RIs adjusted so that the phase phi of the structure is substantially equal to the wave front tilt angle psi. The phase delay of the vertical supply line can also be adjusted by, for example, changing the length of the conductor.

For example, by means of a self-capacitance C_RThe reactance provided is calculated as 1/j ω C_R. Note that the total capacitance of structure 306a may also include a charge terminal T_RAnd the lossy conducting medium 203, wherein the total capacitance of structure 306a may be based on the self-capacitance C_RAnd any bound capacitance, as can be appreciated. According to one embodiment, the charge terminal T_RMay be raised to a height such that any bound capacitance is substantially reduced or eliminated. The presence of bound capacitance may be determined by the charge terminal T_RAnd the capacitance measurement of the lossy conductive medium 203, as previously discussed.

By discrete component coils L_RThe inductive reactance provided may be calculated as j ω L, where L is the coil L_RThe lumped component inductance of (1). If the coil L_RTo distribute the components, their equivalent endpoint inductive reactances may be determined by conventional methods. To tune the structure 306a, adjustments will be made to make the phase delay equal to the wave front tilt for the purpose of matching the surface waveguide mode at the operating frequency. In this condition, the receiving structure may be considered to be "mode-matched" to the surface waveguide. A transformer surrounding structural link and/or impedance matching network 324 may be inserted between the probe and the electrical load 327 in order to couple power to the load. Inserting the impedance matching network 324 between the probe terminal 321 and the electrical load 327 may achieve a conjugate matching condition for maximum power transfer to the electrical load 327.

When placed in the presence of surface currents at the operating frequency, power is delivered from the guided surface wave to the electrical load 327. To this end, electrical load 327 may be coupled to structure 306a via magnetic coupling, capacitive coupling, or conductive (direct tap) coupling. The components of the coupling network may be centralized components or distributed components, as may be appreciated.

In the embodiment shown in fig. 18B, magnetic coupling is used, wherein the coil L is_sAs opposed to the coil L_RThe secondary coil of (2) is positioned, the coil L_RActing as a transformer primary. Coil L_SCan be chain-coupled to the coil L by geometrically winding the coil around the same core structure and adjusting the coupling flux_RAs can be appreciated. Additionally, although the receiving structure 306a includes series-tuned resonators, parallel-tuned resonators or even distributed element resonators with appropriate phase delay may be used.

Although a receiving structure immersed in an electromagnetic field can couple energy from that field, it will be appreciated that the polarisation matching structure works best by maximising coupling and should comply with the conventional rules for coupling with waveguide mode probes. For example, TE₂₀(transverse electric mode) waveguide probe can be optimally used in TE₂₀Conventional waveguides excited in a mode extract energy. Similarly, in this case, the mode-matched and phase-matched receiving structures may be optimized for coupling power from the guided surface wave. Guided surface waves excited by guided surface waveguide probe 200 on the surface of lossy conducting medium 203 can be considered to be the waveguide modes of an open waveguide. The source energy can be fully recovered, excluding waveguide losses. Useful receiving structures may be E-field coupled, H-field coupled or surface current excited.

The receiving structure may be tuned to increase or maximize coupling with the guided surface wave based on the local characteristics of the lossy conducting medium 203 in the vicinity of the receiving structure. To do this, the phase delay (Φ) of the receiving structure may be adjusted to match the wave front tilt angle (Ψ) of the surface traveling wave at the receiving structure. If configured appropriately, the receiving structure may then be tuned for resonance at a composite depth z-d/2 relative to an ideal conductive image ground plane.

For example, consider a receiving structure comprising the tuned resonator 306a of FIG. 18B, which includes a coilL_RAnd is connected to the coil L_RAnd a charge terminal T_RVertical supply lines in between. With charge terminals T positioned at a defined height above the lossy conducting medium 203_RLoop L of_RAnd the total phase shift Φ of the vertical supply line may be matched to the wavefront tilt angle (Ψ) at the location of the tuned resonator 306 a. From equation (22), it can be seen that the wave front tilt is asymptotically transferred to

Wherein epsilon_rContains relative permittivity, and σ₁For the conductivity, epsilon, of the lossy conducting medium 203 at the location of the receiving structure_oPermittivity of vacuum, and ω ═ 2 π f, where f is the excitation frequency. Thus, the wavefront inclination angle (Ψ) can be determined from equation (97).

Tuning the total phase shift (Φ ═ θ) of resonator 306a_c+θ_y) Including via a coil L_RPhase delay (theta) of_c) And phase delay (theta) of vertical supply line_y). Conductor length l along vertical supply line_wMay be delayed by theta_y＝β_wl_wto give wherein β_wIs the propagation phase constant of the vertical supply line conductor. The phase delay due to the coil (or spiral delay line) is θ_c＝β_pl_CWherein the entity length is l_CAnd a propagation factor of

Wherein V_fIs a structural velocity factor, λ_oTo supply a wavelength at a frequency, and_pis composed of a speed factor V_fThe resulting propagation wavelength. Phase delay (theta)_c+θ_y) One or both of which may be adjusted to match the phase shift Φ to the wavefront tilt angle (Ψ). For example, the tap position may be at coil L of FIG. 18B_RTo is provided withAdjusting to adjust coil phase delay (theta)_c) To match the total phase shift to the wavefront tilt angle (phi psi). For example, a portion of the coil may be bypassed by a tap connection as illustrated in the fig. 18B diagram. The vertical supply line conductor may also be connected to the coil L via a tap_RThe position of the tap on the coil can be adjusted to match the total phase shift to the wave front tilt angle.

Once the phase delay (Φ) of the tuned resonator 306a has been adjusted, the charge terminal T may be adjusted_RTo tune to resonate at a composite depth z-d/2 with respect to the ideal conductive image ground plane. This can be done by adjusting the charge terminal T₁Without changing the coil L_RAnd the traveling wave phase delay of the vertical supply line. The adjustments are similar to those described with respect to fig. 9A and 9B.

The impedance to the composite image plane as seen in the "look down" lossy conducting medium 203 is given by:

Z_in＝R_in+jX_in＝Z_otanh(jβ_o(d/2))， (99)

whereinFor a vertically polarized source on earth, the depth of the composite image plane can be derived from:

wherein mu₁Is to lose the permeability of the conductive medium 203, and is₁＝ε_rε_o。

At the base of the tuned resonator 306a, the impedance seen "looking up" into the receiving structure is Z_↑＝Z_SubstrateAs illustrated in fig. 9A. In the case of a terminal impedance of:

wherein C is_RIs a charge terminal T_RThe impedance seen in the vertical supply line conductor "looking up" to the tuned resonator 306a is given by:

and "looking up" down the coil L of the tuned resonator 306a_RThe impedance in (a) is given by:

by directing a "look down" into the reactive component (X) seen in the lossy conducting medium 203_in) And the reactive component (X) seen in the "look up" tuned resonator 306a_Substrate) Matching, coupling in the guided waveguide modes can be maximized.

Referring next to fig. 18C, an example of a tuning resonator 306b is shown that does not include a charge terminal T at the top of the receiving structure_R. In this embodiment, the tuning resonator 306b does not include coupling to the coil L_RAnd a charge terminal T_RVertical supply lines in between. Thus, tuning the total phase shift (Φ) of resonator 306b involves only passing through coil L_RPhase delay (theta) of_c). As with the tuned resonator 306a of FIG. 18B, the coil phase delay θ_cMay be adjusted to match the wavefront tilt angle (Ψ) determined from equation (97), resulting in Φ — Ψ. Although power extraction is possible with a receiving structure coupled into a surface waveguide mode, it is difficult to tune the receiving structure to maximize coupling with a guided surface wave without the need for a charge terminal T_RVariable reactive load is provided.

Referring to FIG. 18D, an exemplary tune is shownA flow chart 180 of an example of shaping a receiving structure to substantially mode match a guided surface waveguide mode on the surface of the lossy conducting medium 203. Starting with 181, if the receiving structure comprises a charge terminal T_R(e.g., the charge terminal of tuned resonator 306a of figure 18B), then at 184, the charge terminal T is connected_RPositioned at a defined height above the lossy conducting medium 203. When the guided surface wave has been established by the guided surface waveguide probe 200, the charge terminal T_RHeight (h) of_p) May be below that physical height of the effective height. The physical height may be selected to reduce or minimize the charge terminal T_RA bound charge (e.g., four times the spherical diameter of the charge terminal). If the receiving structure does not include the charge terminal T_R(e.g., the charge terminal of tuned resonator 306b of fig. 18C), then flow proceeds to 187.

At 187, the electrical phase delay Φ of the receiving structure is matched to the complex tilt angle Ψ defined by the local characteristics of the lossy conducting medium 203. Phase delay (theta) of spiral coil_c) And/or phase delay (theta) of vertical supply line_y) Can be adjusted so that Φ equals the angle (Ψ) of the wave front tilt (W). The wavefront inclination angle (Ψ) may be determined from equation (86). The electrical phase Φ wavefront tilt angles can then be matched. For example, the electrical phase delay Φ ═ θ_c+θ_yBy making the coil L_RAnd/or the length (or height) of the vertical supply line conductor.

Next at 190, the charge terminal T_RThe load impedance of (a) may be tuned to resonate the equivalent image plane model of the resonator 306 a. The depth (d/2) of the conductive image ground plane 139 (fig. 9A) below the receiving structure can be determined using equation (100) and the values of the lossy conductive medium 203 (e.g., earth) at the receiving structure, which can be measured locally. Using composite depth, the phase shift (θ) between the ground plane 139 and the solid boundary 136 (FIG. 9A) of the lossy conducting medium 203 is imaged_d) Theta may be used_d＝β_od/2. As seen "looking down" into the lossy conducting medium 203 (Z)_in) The decision can then be made using equation (99).This resonance relationship may be considered to maximize coupling with the guided surface wave.

Based on a coil L_RThe speed factor, phase delay and coil L can be determined by adjusting the parameters and the length of the vertical supply line conductor_RAnd the impedance of the vertical supply line. In addition, the charge terminal T can be determined using, for example, equation (24)_RSelf-capacitance (C)_R). Coil L can be determined using equation (98)_Rpropagation factor (. beta.) of_p) and the propagation phase constant (β) of the vertical supply line can be determined using equation (49)_w). Using coils L_RAnd the self-capacitance and measured value of the vertical supply line, looking "up" towards the coil L_RThe impedance (Z) of the tuned resonator 306a as seen in_Substrate) The determination may be made using equations (101), (102), and (103).

The equivalent image plane model of fig. 9A is also applicable to the tuned resonator 306a of fig. 18B. Tuning resonator 306a may be accomplished by adjusting charge terminal T_RIs loaded with a load impedance Z_RTuned to resonate with respect to the composite image plane to cause Z_SubstrateReactance component X of_SubstrateCounteracting Z_inX of (2)_inReactive component or X of_Substrate+X_in0. Thus, the impedance at the real volume boundary 136 (fig. 9A) when "looking up" into the coil of the tuned resonator 306a is the impedance at the real volume boundary 136 when "looking down" into the lossy conducting medium 203. Load impedance Z_RBy making the charge terminal T_RCapacitance (C)_R) Changing without changing the passing charge terminal T_RThe observed electrical phase delay phi is theta_c+θ_yTo adjust. An iterative approach may be taken to tune the load impedance Z_RFor resonance of the equivalent image plane model with respect to the conductive image ground plane 139. In this way, coupling of the electric field to the guided surface waveguide mode along the surface of the lossy conducting medium 203 (e.g., earth) may be improved and/or maximized.

Referring to figure 19, the magnetic coil 309 contains a receiving circuit coupled to an electrical load 336 via an impedance matching network 333. To facilitate reception and/or extraction of electricity from guided surface wavesPower, magnetic coil 309 may be positioned so as to direct the magnetic flux of the surface waveThrough the magnet wire coil 309, a current is thereby induced in the magnet wire coil 309 and an endpoint voltage is generated at its output terminal 330. The magnetic flux of the guided surface wave coupled to the single turn coil is represented by

WhereinFor coupling magnetic flux, mu_rIs the effective relative permeability, μ, of the core of the magnetic coil 309_oIn order to achieve a magnetic permeability in a vacuum,as a vector of the intensity of the incident magnetic field,is a unit vector normal to the cross-sectional area of the turn, and A_CSThe area enclosed by each ring. For N turns of the magnet wire coil 309 oriented for maximum coupling with an incident magnetic field that is uniform over the cross-sectional area of the magnet wire coil 309, the open circuit induced voltage appearing at the output terminal 330 of the magnet wire coil 309 is

Wherein the variables are defined above. The magnetic coil 309 may be tuned to the guided surface wave frequency as a distributed resonator or with an external capacitor across its output terminal 330 (as the case may be) and then impedance matched with a surface electrical load 336 via a conjugate impedance matching network 333.

Assuming that the resulting electrical circuit provided by the magnetic coil 309 and the electrical load 336 is properly adjusted and conjugate impedance matched via the impedance matching network 333, the current induced in the magnetic coil 309 may be used to optimally power the electrical load 336. The receiving circuit provided by the magnetic coil 309 provides the advantages of: it is not necessary for the receiving circuit to be physically connected to ground.

Referring to fig. 18A, 18B, 18C and 19, the receive circuitry provided by the linear probe 303, the mode-matching structure 306 and the magnetic coil 309 each facilitate receiving electrical power transmitted as in any of the embodiments of guided surface waveguide probe 200 described above. To this end, the received energy may be used to supply power to the electrical load 315/327/336 via a conjugate matching network, as may be appreciated. This is in contrast to signals that may be received in a receiver, which are transmitted in the form of a radiated electromagnetic field. Such signals have very low available power and the receiver of such signals does not load the transmitter.

The characteristics of the guided surface wave of the present invention generated using guided surface waveguide probe 200 as described above also provide that the receive circuitry provided by linear probe 303, mode matching structure 306 and magnetic coil 309 will load excitation source 212 (e.g., fig. 3, 12 and 16) applied to guided surface waveguide probe 200, thereby generating a guided surface wave to which the receive circuitry is subjected. This reflects the fact that: the guided surface wave generated by a given guided surface waveguide probe 200 as described above contains transmission line modes. By contrast, the power supply driving the radiation antenna generating the radiation electromagnetic wave is not loaded by the receivers, regardless of the number of receivers used.

Thus, the one or more guided surface waveguide probes 200 together with the one or more receiving circuits in the form of linear probes 303, the tuned modal matching structure 306 and/or the magnetic coil 309 may constitute a wireless distribution system. Given that the guided surface wave transmission distance using guided surface waveguide probe 200 as set forth above is frequency dependent, it is possible that wireless power distribution can be achieved across a wide area and even globally.

Conventional wireless power transfer/distribution systems that are currently under extensive research include "energy harvesting" from radiated fields as well as sensors coupled to inductive or reactive near fields. In contrast, the wireless power system of the present invention does not waste power in the form of radiation, which would never be lost if not intercepted. The disclosed wireless power system is also not limited to very short range as with conventional mutually reactively coupled near field systems. The wireless power system disclosed herein is coupled with a novel guided surface transmission line modal probe that is equivalent to delivering power to a load through a waveguide or directly wired to a load of a remote generator. Without counting the power required to maintain the transmitted field strength plus the power dissipated in the surface waveguide (this power is insignificant at very low frequencies relative to the transmission losses in a conventional high voltage power line at 60 Hz), all generator power goes only to the desired electrical load. When the electrical load demand is terminated, source power generation is relatively idle.

Referring next to fig. 20A-E, examples of various schematic symbols are shown, which are used with reference to the discussion that follows. With particular reference to fig. 20A, a representative guided surface waveguide probe 200A, 200b, 200c, 200e, 200d, or 200f is shown; or any variation thereof. In the following figures and discussion, the description of this symbol will be referred to as a guided surface waveguide probe P. For simplicity in the following discussion, any reference to a guided surface waveguide probe P is to any of guided surface waveguide probes 200a, 200b, 200c, 200e, 200d, or 200 f; or a variation or combination thereof.

Similarly, referring to fig. 20B, a symbol is shown representing a guided surface wave receiving structure that may include any of the linear probe 303 (fig. 18A), the tuned resonator 306 (fig. 18B-18C), or the magnetic coil 309 (fig. 19). In the following figures and discussion, the description of this symbol will be referred to as the guided surface wave receive structure R. For simplicity in the following discussion, any reference to a guided surface wave receiving structure R is a reference to any of the linear probe 303, the tuned resonator 306, or the magnetic coil 309; or a variation or combination thereof.

In addition, referring to fig. 20C, anSpecifically, a symbol indicating the linear probe 303 (fig. 18A) is shown. In the following figures and discussion, the description of this notation will be referred to as guided surface wave receive architecture R_P. For simplicity in the following discussion, the guided surface wave receiving structure R is described_PAny reference to (a) is a reference to the linear probe 303 or a variation thereof.

Additionally, referring to fig. 20D, symbols are shown that specifically represent the tuned resonator 306 (fig. 18B-18C). In the following figures and discussion, the description of this notation will be referred to as guided surface wave receive architecture R_R. For simplicity in the following discussion, the guided surface wave receiving structure R is described_RAny reference to (a) is a reference to the tuned resonator 306 or a variation thereof.

Further, referring to fig. 20E, a symbol specifically representing the magnetic coil 309 (fig. 19) is shown. In the following figures and discussion, the description of this notation will be referred to as guided surface wave receive architecture R_M. For simplicity in the following discussion, the guided surface wave receiving structure R is described_MAny reference to (a) is to the magnetic coil 309 or a variation thereof.

2. Object recognition

General overview of (A)

Referring additionally to fig. 21 and 22, schematically illustrated is an embodiment of an object identification system 400 that uses a guided surface wave as described in the previous section to power one or more response tags 402. It will be emphasized again that the figures are not necessarily to scale.

Each tag 402 may be associated with an object 404. The object 404 may be any type of article of manufacture. Exemplary objects 404 include, but are not limited to, consumer items, a group of goods, articles of clothing, food, packaging for articles, containers for multiple articles, vehicles, shelves with stacked goods, shipping containers, or any other item that needs to be tracked.

Object recognition system 400 includes an interrogator 406. In the embodiment of FIG. 21, interrogator 406 includes guided surface waveguide probe P and co-located receiver 408. The probe P and receiver 408 may be housed in the same structure, such as a radome, decorative envelope, or the like. In this embodiment, interrogator 406 typically has a fixed location.

In the embodiment of fig. 22, the probe P and the receiver 408 are not co-located. As will be described, the probe P and the receiver 408 may have a physical relationship (e.g., both may be deployed in a facility) or may have no or very little physical association. In this embodiment, the probes P and receivers 408 functionally form the interrogator 406, but need not be deployed by the same party, need not be co-located, and need not be considered a unit. In this embodiment, the probe P typically has a fixed position and may be housed in a suitable structure such as a radome or decorative envelope. The receiver 408 may have a fixed location or may be portable. For example, the receiver 408 may be hand-held and used by a person, such as a person moving about a vehicle or a person securable to a vehicle, such as a truck, forklift, airplane, cargo ship, or the like.

In the embodiment of fig. 21 and 22, probe P transmits guided surface waves along underlying terrestrial medium 410 as described in the previous section. The land medium 410 may be any suitable lossy conducting medium such as, but not limited to, the earth, a warehouse floor, a warehouse, a factory or other facility, or any other suitable substrate. As depicted, probe P does not generate a radiant wave, but emits a guided surface wave along the surface of medium 410. The energy emitted from the probe P is transmitted as a netke surface current to one or more tags 402 located within the effective transmission range of the guided surface waveguide probe P. The probes P may be configured as any of the probes described above or in any other suitable configuration.

Referring additionally to fig. 23, a representative label 402 is schematically illustrated. The tag 402 is configured more like an RFID tag and includes an antenna 412 and tag circuitry 414 mounted to a substrate 416, such as a sheet of paper or plastic. Substrate 416 may include an adhesive to attach label 402 to object 404. Other fastening techniques may be used or the tag 402 may form part of the object 404. In another embodiment, the tag may be located inside the object 404 or the electrical components of the tag 402 may form part of the electrical components of the object 404.

In typical embodiments, rather than drawing power from the guided surface waves, tag 402 does not have a power source, such as a battery or physical connection to an external power source. Instead, the tag 402 is responsive to a guided surface wave having one or more frequencies. For example, electromagnetic energy from the guided surface wave generated by probe P induces a current in antenna 412, and this current is coupled to and used to power tag circuitry 414. Similar to the manner in which RF energy powers a conventional RFID tag, powering the tag circuitry 414 in this manner may be referred to as illuminating the tag 402. However, in contrast to conventional RFID tags, the tag circuitry 414 may load the probes P.

Tag circuitry 414 may include any suitable electrical components and may be configured to perform any suitable function. For example, the tag circuitry 414 may include a memory that stores data such as, but not limited to, an identifier that may be used to identify the associated object 404. The identifier may represent a type of cargo, such as stock-keeping units (SKUs). SKUs are unique identifiers for each distinct product available in commerce. Alternatively, the identifier may represent a specific item, such as a unique identifier that distinguishes an object from all other objects including nominally identical objects (e.g., objects having the same SKU). The tag circuitry 414 may read the identifier from memory and transmit an RF signal containing the identifier in a data message format via the antenna 412 (or a second antenna, not shown). In another embodiment, the tag 402 may respond by emitting a guided surface wave, but an RF return signal may be more desirable to generate due to the desire to keep the tag 402 relatively small, flat, and power efficient.

In one embodiment, the tag is addressable and has a unique address, such as a Media Access Control (MAC) address or an Internet protocol version 6 (IPv 6) address, which includes hierarchical addressing. In one embodiment, the identifier of the tag is the same as the address of the tag.

The RF signal transmitted by the tag 402 may be received by a receiver 408. The receiver 408 may analyze the signal to determine the identifier. In one embodiment, the receiver 408 communicates the identifier and any other suitable information collected during reading of the tag 402 to the computer system 418 (fig. 21 and 22). For these purposes, the receiver 408 may include: an antenna and radio circuit that receives RF signals transmitted by the tag 402; processing circuitry to perform any suitable function in conjunction with reading, storing, analyzing, and processing data (e.g., location data, time of arrival, or signal strength, as described below) received from tag 402 or determined at the time of receipt; and a communications interface for establishing operative communications with computer system 418. Thus, the receiver 408 may include: a memory storing data and logic instructions; and a processor for executing the logic instructions. Alternatively, computer system 418 and receiver 408 may be combined.

After receiving the identifier, computer system 418 can perform one or more functions appropriate for the received identifier. Various exemplary functions performed by the computer system 418 will be described in greater detail below.

Receiver 408 and computer system 418 can communicate via a communication medium 420. Communication medium 420 may include one or more of the following: a direct wired connection (e.g., a USB interface), a direct wireless connection (e.g., a bluetooth interface), a wide area network connection (e.g., via internet communications), or a local area network (e.g., via corporate network or WiFi network communications), among others. In some embodiments, the computer system 418 may also communicate with the probe P, such as controlling the generation of the guided surface wave in terms of the time the guided surface wave is generated, the duration of the guided surface wave generation, the frequency of the guided surface wave, and so forth.

2(B) powering tags with guided surface waves

Powering RFID tags is limited for forward links. More specifically, conventional RFID tags are illuminated and read by a conventional RFID interrogator (also known as an RFID reader). RFID interrogators transmit RF signals using relatively small and directional antennas. The transmitted RF energy is typically limited by regulatory agencies, such as the Federal Communications Commission (FCC) in the united states. Limitations are proposed to avoid impermissible interference with other systems and to avoid the emission of potentially harmful radiation. Thus, in order to deliver sufficient energy to a conventional RFID tag using a conventional RFID frequency (e.g., near 900MHz or at an assigned frequency of 13.56 MHz) to power the tag's circuitry and elicit an RF response, close proximity between the conventional RFID interrogator and the conventional RFID tag is required. In most cases, the maximum distance between the RFID interrogator and the RFID tag for effective reading is a few meters, and may be short when the return signal from the RFID tag relies on inductive coupling with the RFID interrogator. In addition, conventional RFID technology has poor penetration in high permittivity and lossy materials, examples of which are water bottles or shelves of water-containing foods. Thus, reading an RFID tag in which high permittivity and lossy materials are inserted between the RFID interrogator and the RFID tag is often unsuccessful.

Conventional RFID technology inherently limits the functionality of RFID tags. More specifically, there are few available power to perform processing functions, memory read operations, memory write operations, data transfer operations, and the like. At the same time, merchants and others are concerned with extending RFID applications for inventory and supply chain control, thereby reducing inventory "shrinkage" caused by product theft and performing other functions.

The techniques disclosed herein overcome these disadvantages and enhance the functionality that can be performed with tagged objects by using guided surface waves to supply a greater amount of power "on target" (e.g., target one or more tags 402). Accordingly, the disclosed technology overcomes the forward link limitations found with conventional RFID tags.

The tag 402 may be considered a load on the probe P and, in most cases, may draw as much power as is needed to perform processing functions, memory read operations, memory write operations, data transfer operations, and the like. Exemplary operations will be described in greater detail below. Furthermore, the distance between the tag 402 and the probe P and the distance between the tag 402 and the receiver 408 can be greatly extended relative to the distance conventionally required between an RFID interrogator and an RFID tag. It should be noted that the forward link powering the tag 402 in the disclosed method may have a link quality that is tens of dB higher than the return link between the tag 402 and the receiver 408. However, system performance would be satisfactory for performing the functions and features described herein, as well as other similar features and functions.

To derive power from the guided surface waves, tag 402 includes an antenna 412. The antenna 412 may be a loop antenna (also referred to as a loop antenna), as schematically illustrated in figure 23, or may be implemented as a magnetic coil 309 as schematically illustrated in figure 19. In other embodiments, the antenna 412 may be configured as a dipole antenna or linear probe 303 as schematically illustrated in FIG. 18A. There may be more than one antenna 412. In this case, the antennas 412 may be of the same type (e.g., loop antenna or dipole antenna) or may be of different types (e.g., loop antenna and dipole antenna). The presence of the loop antenna and the dipole antenna substantially in the same plane or parallel planes (e.g., both in substrate 416) may facilitate powering of the tag regardless of the orientation of the tag. This is because at least one of the antennas is better aligned with the magnetic component of the guided surface wave or the electrical component of the guided surface wave (which are normal to each other). Thus, depending on the spatial orientation of the tag, a loop antenna may be the dominant provider of electrical power from the magnetic component of the guided surface wave to the tag circuitry 414, or a dipole antenna may be the dominant provider of electrical power from the electrical component of the guided surface wave to the tag circuitry 414. It is further contemplated that many conventional RFID tag antenna designs may use or be modified to convert sufficient energy from the guided surface waves into electrical energy to power the tag circuitry 414.

The tag circuitry 414 may include an impedance matching network as described above. In some embodiments, the impedance matching network will be statically arranged or may be omitted. Statically arranged or omitted impedance matching networks may not yield maximum energy conversion efficiency, but will make the tag circuitry 414 relatively simple and accommodate frequent movement of the tag 402 without having to reconfigure the impedance matching network based on its position relative to the lossy conducting medium 410. Regardless of the specific arrangement of the antenna 412, the tag 402 may be viewed as including a guided surface wave receiving structure R as described above in connection with FIGS. 1-20E.

The label 402 may be relatively small and light. Most tags 402 will be similar to RFID tags in size and weight. For example, the label 402 can be relatively flat (e.g., about 1mm thick or less), ranging from about 1cm long to about 10cm long, and ranging from about 1cm wide to about 10cm wide.

As will be described, the guided surface wave that acts as a forward link to deliver power from probe P to tag 402 may have one frequency, and tag 402 may transmit a return link signal at a second frequency to transmit data to receiver 408. To increase the performance and throughput of the plurality of tags 402 operating at low power, the second frequency may be higher (e.g., one or more orders of magnitude higher) than the first frequency. To accommodate the transmission of the return link signal at high frequencies, tag 402 may include a second antenna 422 in situations where antenna 412 is not capable of efficiently transmitting the return link signal.

The system 400 may be configured to take advantage of the properties of guided surface waves as described above. Thus, the actual use of guided surface waves at relatively low frequencies may be made in connection with object recognition. In one embodiment, the frequency of the guided surface wave emitted by the probe is about 13.56MHz or other frequency that has been authorized by the appropriate regulatory agency for use with RFID technology. Frequencies above or below 13.56MHz may be used depending on the object recognition application and the desired characteristics of the guided surface wave. The architecture of the tag 402, including the antenna configuration and/or impedance matching, may be coordinated with the frequency of the guided surface wave to achieve energy transfer.

As described above, the field strength of the guided surface wave remains relatively high for distances from knee 109 (fig. 1) of probe P that are less than guided field degree curve 103. Thus, a single probe P can be used to power many tags 200 within the active area surrounding the probe P while maintaining an acceptable energy density at the location of the probe P. For example, Effective Isotropic Radiated Power (EIRP) at an energy source used in connection with an object identification application may be imposed by regulatory agencies. Typical limits for conventional RFID applications are about one or two watts. It is reasonable to assume that this type of EIRP limitation will be maintained for some types of object recognition applications that use guided surface waves. Even under these constraints, a single probe P may be able to power hundreds, thousands, or millions of tags 402 located within a radial distance from the probe P that is less than the distance of the knee 109 of the corresponding guide field profile 103 from the probe P. For an omnidirectional probe P, the active area of the illuminatable label is a circular area having a radius of about the distance of the knee 109 of the corresponding guide field profile 103 from the probe P. The distance of knee 109 from probe P depends on the frequency of the guided wave. As an example, knee 109 for a guided surface wave at about 13MHz is approximately one kilometer from probe P, depending on ground properties. In a relatively ideal situation, conventional RFID technology operating at 900MHz has an effective operating range of about 30 meters. Thus, it will be appreciated that the tag 402 may be powered from a greater distance and at a much lower frequency than previously possible.

The tag 402 may be configured to respond (e.g., become powered and/or transmit a return signal) when illuminated with a guided surface wave of a predetermined frequency, frequencies, or frequency range. In one embodiment, the tags 402 are configured to respond to a first frequency but not a second frequency, and different tags 402 are configured to respond to a second frequency but not a first frequency. In one embodiment, a minimum separation between the first frequency and the second frequency may be established, such as about a 10kHz separation or a 100kHz separation.

As will be appreciated, many tags 402 may be efficiently powered with guided surface waves, and the tags 402 may be configured to implement relatively power intensive functions. Many of these functions will be described below. Furthermore, the use of inductive readers with limited operating distances can be avoided. This allows the tag 402 to be interrogated at significant distances and/or with a relatively low frequency. The nature of the guided surface wave also allows interrogation of the tag 402 in situations where high permittivity material and/or lossy material is interposed between the probe P and the tag 402. As an example, a tag 402 located within a shelf of goods or a shipping container of goods having water content (e.g., aqueous foods such as water bottles, beer, soup, sauces such as ketchup or satay sauce, etc.) may be interrogated. In one embodiment, the tag 402 may be powered to operate when one to five meters of water is inserted between the probe P and the tag 402.

2(C) tag interrogation

One or more tags 402 may be interrogated (also referred to as read) by illuminating the tag 402 with a guided surface wave having a frequency compatible with the tag 402 and receiving a return signal from the tag 402 with a receiver 408. As part of this process, the tag 402 draws power from the guided surface wave to power the electronic components (tag circuitry 414) in the tag 402. The drawing of power may be passive operation. In particular, the guided surface waves induce a current in the antenna 412 that is applied to the tag circuitry 414. Application of power to the tag circuitry 414 enables the tag circuitry 414 to implement one or more predetermined functions. An exemplary predetermined function is to read a tag identifier associated with the tag 414 from the memory component of the tag circuitry 414 and transmit a return signal containing the tag identifier. The return signal may be in the form of a data transmission that follows a predetermined protocol in terms of transmission time (e.g., a predetermined time slot under time division multiplexing with return signals of other tags), electrical characteristics, message format or content, encryption, and the like. The signal may be received and interpreted by a receiver 408.

In one embodiment, the return signal may be an RF signal. The propagation capability of the return signal will depend on the characteristics of the RF signal, such as energy level, data encoding and frequency. The distance at which the return signal can be effectively detected by the receiver 408 will depend on the ability of the return signal to propagate in the surrounding environment and the sensitivity of the receiver 408. To allow reading at relatively large distances, such as greater than 30 meters, the return signal may be transmitted with a relatively large EIRP. Drawing power from the guided surface wave will allow the transmitter in the tag circuit 414 to radiate at a relatively high power because the energy density of the power available in the source (guided surface wave) is high. Additionally, the return signal may have a frequency that is relatively high to enhance the flow rate. In one embodiment, the return signal may have a frequency that is higher than the frequency of the illuminating guided surface wave, such as about one to three orders of magnitude higher than the frequency of the guided surface wave. For example, if the guided surface wave is in the range of about 10MHz to about 250MHz, the return signal may be in the range of about 100MHz to about 5.4GHz or higher.

Thus, the guided surface wave may be at one frequency (e.g., a first frequency), and the tag 402 may respond at a second frequency different from the first frequency. In other embodiments, the response frequency may be nominally the same as the guided surface wave frequency. In one embodiment, a first set of tags 402 responsive to a guided surface wave at a first frequency may respond at a second frequency, and a second set of tags 402 responsive to a guided surface wave at the first frequency may respond at a third frequency different from the second frequency. Using the difference in response frequencies, the tags in the first set are distinguishable from the tags in the second set.

As indicated, one or more predetermined functions may be implemented by the tag 402 when the tag circuitry 414 becomes enabled. One exemplary predetermined function is to transmit a return signal. The return signal may contain information such as one or more of the following: an indication that no identifying information exists for the tag 402, an indication of the type of tag 402 or the type of object 404 associated with the tag 402, a SKU or other identifier for the object 404 associated with the tag 402, a unique identifier or address of the tag 402 that distinguishes the tag 402 from other groups of tags 402 or all other tags 402, or any other data stored by the tag 402.

In one embodiment, the transmission of the return signal is automatic. In other embodiments, a response or other action by tag 402 may be implemented under certain conditions. In an exemplary embodiment, the tag 402 is addressable and responsive to messages or data addressed to the tag 402. The tags 402 may be individually addressable depending on the addressing scheme. For this purpose, the tag 402 may have any address that is unique to the address of all other tags 402, such as an IPv6 address or some other address in an appropriate format. In one embodiment, the address may have a length of about 40 bits to about 64 bits. It is contemplated that an address 64 bits long or longer may be used to uniquely address each object on the planet. In other embodiments, a message or command may be addressed to multiple tags 402. For this purpose, the tags 402 may share a common address (e.g., all tags 402 associated with a SKU may have the same address) or hierarchical addressing may be used to utilize other unique addresses. Other exemplary data distribution techniques include multicast addressing or geo-multicasting.

The use of addressable tags 402 allows various predetermined functions to be implemented by the tags 402. As an example, a data link or communication interface (e.g., a bluetooth interface) between the receiver 408 and the tag 402 may be established for bidirectional exchange of data. Communication between the receiver 408 and the tag 402 may allow the receiver 408 (or the computer system 418 via the receiver 408) to poll the tag 402 for information stored by the tag 402 or send a command to the tag, or may allow the tag 402 to receive and store additional information.

In another embodiment, the predetermined function implemented by tag 402 includes storing data encoded in the guided surface wave or implementing commands encoded in the guided surface wave. Data or commands in the guided surface wave to which the tag 402 responds may be broadcast to the tag 402 without addressing or may be addressable to one or more specific tags 402. For this purpose, the probe P may include a coded carrier message in the guided surface wave.

The predetermined functions that may be implemented by one or more tags 402 when transmitting data and/or commands through the receiver 408 or that may be part of a guided surface wave may include, but are not limited to, writing data of the tags 402 to memory, executing commands, responding to requested information, and responding by transmitting a return signal only if addressed or otherwise polled.

Another predetermined function may be to cease transmitting return signals in response to a message or appropriate command acknowledging receipt of return signals. This function can be used in various situations. For example, during inventory control operations, a guided surface wave may be used to illuminate many tags 402, all of which may begin response operations by transmitting respective return signals. When a response from a respective tag 402 is received and processed, the computer system 418 may issue a command (via the receiver 408 or guided surface wave) to the tag 402 from which the return signal was received and processed to cease transmitting the return signal. In this way, return signals from other tags 402 may be received and processed with less contention.

In one embodiment, it is possible that tag 402 may be permanently "turned off" or disabled by executing commands in tag 402. For example, after the object 404 is purchased by a consumer, its associated tag 402 may be deactivated so that the tag will no longer perform the predetermined function when illuminated by the appropriately directed surface wave.

2(D) regionalized label illumination

Reference is additionally made to fig. 24. Fig. 24 shows two adjacent sites 424a and 424 b. Sites 424 in the illustrated embodiment are buildings that each house a retail store (retail inventory). This exemplary embodiment is shown for descriptive purposes. It will be appreciated that the illustrated embodiments represent aspects of the disclosed concept. The nature and configuration of the sites to which the principles of the disclosed concepts are applicable may vary. Types of sites include, but are not limited to, retail stores, warehouses, office facilities, schools, ports, distribution centers, shipping and sorting centers, sports venues, parking lots, factories or manufacturing facilities, farms, military bases, and the like. The site may not include any building structure or may include one or more building structures. Each location is characterized by a known geographic region in which illumination and reading of the tag 402 is desired. Due to the relative sizes of the tags 402 and the sites, the individual tags 402 and associated objects 404 are shown in FIG. 24 for simplicity of illustration. It should be understood that tags 402 and associated objects 404 are present within each site 424. The number of tags 402 and associated objects 404 in the site 424 may vary, and may range from as few as one tag 402/associated object 404 to millions of tags 402/associated objects 404.

In the illustrated embodiment, sites 424a and 424b are spaced apart. Adjacent sites 424 need not be spaced apart. The sites 424 corresponding to buildings may touch or nearly touch each other, or may share walls that distinguish one site 424 from another.

In one embodiment, a probe P is associated with each site 424. Typically, probe P is located within a geographic region defining site 424. One or more receivers 408 are also associated with the site 424 and located at the site 424. Typically, the receivers 408 associated with the site 424 are located within a geographic region that defines the site 424, but one or more of the receivers 408 associated with the site 424 may be located outside of this geographic region, such as near the entrance of the site 424.

Each probe P is configured to illuminate a tag 402 located within the geographic region of the site 424 associated with probe P. In one embodiment, a probe P associated with one site 424 is configured to not illuminate a tag 402 located within an adjacent site 424. It will be appreciated that it may not always be possible or practical to not illuminate the tags 402 in adjacent sites, and/or that, at times, the tags 402 in adjacent sites may be inadvertently illuminated even if care is taken to limit the operable range of the probe P.

For the purpose of configuring the probe P not to illuminate the label 402 in an adjacent site, a natural "energy bubble" due to the generation of a guided surface wave by the probe P may be used. As described above, the energy density of the guided surface wave whose roll-off is at a distance less than the distance of knee 109 from probe P is extremely low. At a distance outward of knee 109, the energy density drops significantly. Assuming that probe P is omnidirectional and the electrical properties of the land boundary medium 410 are uniform along the operative interface between probe P and land boundary medium 410, the energy density behaves in this manner in all radial directions from probe P. The distance of the knee 109 varies with the frequency of the guide wave. Further, for purposes of this specification, to be considered illuminated, the tag 402 must be in the presence of a threshold energy density to draw sufficient power from the guided surface wave to power and be able to respond. The threshold energy density may depend on the energy consumption characteristics of the tag 402 and may therefore vary.

For a tag 402 that is operably compatible with the frequency of the guided surface wave generated by the probe P, the area surrounding the probe P where the tag 402 will be exposed to the threshold energy density to become irradiated will be referred to as the irradiated area 426. As illustrated in the exemplary embodiment of fig. 24, one irradiation field 426a is associated with site 424a and probe Pa, and another irradiation field 426b is associated with site 424b and probe Pb. In embodiments where the frequency of the guided surface waves generated by the probes Pa and Pb for adjacent sites 424a, 424b are operably compatible with the tags 402 for the other of the adjacent sites 424a, 424b, the creation of non-overlapping illumination zones 426 will allow each site 424 to perform object identification by reading the tags 402 independently of each other.

Specifically, the guided surface wave generated by the probe Pa for site 424a will not tend to illuminate the label in the adjacent site 424b and vice versa. Additional precautions may be made to avoid having the receiver 408 for one site 424a detect a response signal from a tag 402 located in an adjacent site 424b when the tag 402 is illuminated by the probe Pb for the adjacent site 424b, and vice versa. These precautions may include controlling the timing of the irradiation so that probes Pa, Pb from respective sites 424a, 424b do not actively generate guided surface waves simultaneously. Another precaution is to limit the output power of the tag 402 to a level low enough to avoid detection by the receiver 408 in other sites, and/or to limit the receive sensitivity of the receiver 408 to avoid detection of signals from tags 402 in adjacent sites 424. Another precaution is to maintain a database of tag identifiers in computer system 418 that processes information from reader 408 at site 424 for all tags 402 that should be present at site 424. If the tag 402 is read and the associated tag identifier is not in the database, the following assumptions may be made: tag 402 is not associated with site 424 and should be ignored. An exception may be made in the entry mode when an object arrives at the site 424 and is interrogated to add a corresponding tag identifier to the database.

It should be noted in view of the foregoing that there are several factors that control the effective size of the illumination area 426, including the power and frequency of the guided surface wave and the power requirements of the tag 402. Thus, each of the power and frequency of the guided surface waves, the characteristics for the tags 402 within the site 424, and the characteristics for the tags 402 in neighboring sites may be selected to coordinate with each other to establish an appropriate size for each illumination area 426. It will be appreciated, however, that frequency is the most important contributor to the size of the illumination zone 426. The frequency in the range of about 100MHz to about 200MHz should be sufficient to control the size of the illumination zone 426 to closely match the size of the locus 424 when the locus 424 is a typical warehouse or retail store.

It may also be desirable to control the shape of the irradiation zone 426. The shape of the illuminated area 426 can be controlled by using a probe assembly having an output that varies as a function of direction. This can be accomplished using multiple probes P to create a convex in the guided surface wave distribution or to create a guided surface wave that is an aggregate of multiple directionally-launched guided surface waves (e.g., multi-beam approach). For example, over-positioning of a single probe P can be used to make a phased array probe with a directional output that is controlled by the presence of multiple simultaneously generated guided surface waves.

By selecting the characteristics of the probes P (or probe assembly) and the tag 402 to control the size and shape of the irradiation region 426, the irradiation region 426 can be made to approximate the geographic region of the associated site 424. Furthermore, as described above, it is possible that one probe P in a site 424 can be used to illuminate all tags 402 in the site 424 (e.g., by achieving a high energy density across the site 424) while maintaining an acceptable energy density at the source (e.g., an EIRP of about 1 watt to about 2 watts at the probe P).

Additional considerations may be used to select the frequency of the guided wave. For example, access to certain frequencies may or may not be utilized for object identification purposes by a regulatory agency supervising the jurisdiction in which the location 424 is located.

Another consideration is the effective height of the guided surface wave. The energy density of the guided surface wave falls at a height of about the wavelength of the guided surface wave. Thus, the height of the illuminated area 426 will be about the wavelength of the guided surface wave. For a guided surface wave of about 13MHz, probe P would be about three feet tall and illumination area 426 would be about 72 feet tall (about 22 meters). This height may be sufficient to illuminate labels 402 associated with objects 404 placed on upper shelves in many bins. For a guided surface wave of about 100MHz, the illumination area 426 will be about 3 meters high, and for a guided surface wave of about 300MHz, the illumination area 426 will be about 1 meter high. These heights are compatible with many retail environments.

2(E) data collection from tags at a site

Various functions may be implemented by reading a tag 402 present at a site. Exemplary functions include inventory control, finding misplaced objects 404, reducing theft, and consumer transaction operations. For these tasks, it is assumed that each object 404 to be tracked is associated with a tag 402, and computer system 418 maintains a database of objects 404 and each associated tag identifier. This information may be generated and/or collected when the tag 402 is first associated with the object 404, which may occur at a location remote from the site 424, such as a factory that manufactured the object. In other cases, this information may be generated and/or collected when the tag 402 arrives at the site.

To perform a read of the tag 402 at the site 424, there are one or more probes P and one or more receivers 408. Because tag 402 may be illuminated by a guided surface wave generated by probe P located outside site 424, probe P need not be located within the geographic region of 424. It is contemplated that each receiver 408 receiving a return signal from a tag 402 located at the site 424 will be located in the geographic region of the site 424 or in proximity to the site 424 (e.g., within a distance capable of receiving a return signal transmitted by a tag 402 in the site 424).

Each receiver 408 for a site 424 may be strategically placed, such as through a door, dock, cash register, etc. For example, in the illustrated embodiment of location 424a, where location 424a is a retail location, receiver 408 is located adjacent a primary entrance 428 through which customers enter and exit, receiver 408 is located adjacent a door 430 separating a primary shopping area 432 from an inventory storage area 434, and receiver 408 is located adjacent a secondary exit door 436 at storage area 434. Another receiver 408 may be positioned adjacent to the discharge station 438 and another receiver 408 may be positioned at the payment area 440. The objects 404 and associated tags 402 may be present on shelves 442 or displays located in the shopping area 432. Additional objects 404 and associated tags 402 may be present on shelves 442 in the storage area 434 or in other locations. There may also be receivers 408 at additional or alternative locations.

With additional reference to the illustration of exemplary site 424b in fig. 24, another arrangement of receiver 408 will be described. In this embodiment, the receiver 408 is placed at a strategic location but is not associated with a specific location within the locus 424b, such as a door, an unloading dock, a payment area, and the like. Instead, the receiver 408 is positioned to detect the return signal emitted by the tag 402 within the site 424. Although two receivers 408 are illustrated in the accompanying figures, other numbers of receivers 408 are possible. For example, there may be only one receiver 408 or there may be three or more receivers 408. The return signal may be used and analyzed in the same manner as described above. The number and positioning of the receivers 408 in either embodiment of the sites 424a or 424b may depend on the operating range between the tag 402 and the receivers 408, the size of the sites 424, the programming of the computer system 418, and any other relevant factors. Further, the receiver arrangement of the embodiment of site 424a may be combined with the receiver arrangement of the embodiment of site 424b, such that some receivers are positioned in connection with certain structural components of the site, and others are positioned at more general strategic locations.

It should be appreciated that the location of the receiver 408 in fig. 24 is exemplary and for descriptive purposes. The number and location of the receivers 408 may be modified depending on the characteristics of the sites 424 and the tag reading function to be performed.

The probe P may be located in a strategic location but may be hidden from view. For example, in an embodiment of site 424a, probe Pa is hidden in end cap 444 of one of shelves 442. The probe P may be configured to continuously generate the guided surface wave so that each tag 402 in the respective illumination region 426 responds continuously, such as by repeatedly transmitting a return signal without a delay between repeated transmissions or periodically repeating the transmission of a return signal (e.g., once a second). In other embodiments, the probe P is controlled to generate a guided surface wave at a desired time and for a desired duration. The time required may be pre-scheduled or may be the result of activation of the trigger probe (e.g., an operator may trigger the probe to conduct an inventory check to find misplaced objects or settle objects for purchase, as described in the exemplary functions below).

The return signal may be detected by one or more receivers 408. Data derived from the return signal (e.g., the tag identifier) along with the known location and/or identity of the receiver 408 that detected the return signal may be used in conjunction with various functions. One exemplary function is to participate in identifying the object 404 that the customer intends to purchase. For example, a customer may bring the object 404 for purchase to the payment area 440. In the embodiment of site 424a, objects 404 may move past receiver 408 at payment region 440, and those objects 404 may be registered by computer system 418. It should be noted that items for purchase need not be read one at a time, similar to the way printed SKUs are continuously scanned with a bar code reader. Instead, multiple objects 404 may be passed through the receiver 408 at the same time. Once the object 404 is identified, the customer may then pay for the item in a conventional manner.

In another embodiment, information about inventory at the site 424 may be tracked. For example, in an embodiment of site 424a, when the object 404 enters or leaves the site 424, the associated tag 402 may pass one of the receivers 408 located at gate 428, gate 436, or gate 438. By keeping track of the objects 404 passing through these receivers 408, the number of objects 404 can be accurately accounted for by object type and detected as moving from an authorized zone to an unauthorized zone. This detection may also be made by detecting movement past a predetermined point or across a boundary between an authorized area and an unauthorized area. In another embodiment, detection that the object remains in the authorization zone may be obtained by failing to receive a return signal from the associated tag within a predetermined amount of time since the last repetition of receiving the return signal. Furthermore, this information may be cross-referenced for valid object purchases and other legitimate reasons why the object may be removed from the site 424 (e.g., shipment to a downstream location in the supply chain or return to the supplier). If the deviation of the object 404 is not associated with a legitimate reason, additional security-related actions may be implemented, such as alerting a governing body (e.g., a manager or police at site 424), opening a security camera and recording video of the area surrounding the exit gate or station through which the object passes, initiating a survey, and so forth.

Other information may be determined based on the manner in which the object 404 entered or exited the site 424, the time of receipt of the return signal, and/or additional information such as when a particular vehicle or worker is also present. For example, in a facility having multiple discharge stations, a discharge station that tracks the movement of objects through may be used to establish which personnel are handling the objects, which truck the objects are loaded onto, or which truck brings the objects to the facility. As another example, tracking an object 404 located in a storage area 434 relative to a shopping area 432 may receive a return signal through a receiver 408 at a door 430. Other data collection can be performed regarding the movement of objects within the locus 424, such as tracking movement from one user-defined zone to another, collecting data regarding the behavior of customers, and so forth.

In another embodiment, an inventory of all objects 404 or certain categories of objects in the site 424 may be made by analyzing the return signal from the tag 402. In one embodiment, the computer system 418 may analyze the tag identifiers associated with each distinct return signal to perform inventory analysis. In one embodiment, de-interleaving (de-interleaving) techniques may be applied to ignore or turn off return signals from tags 402 having associated tag identifiers that have been registered in the inventory analysis. To limit the number of tags 402 that respond during inventory analysis, an addressing command that transmits a return signal may be sent to the particular tag 402 of interest. Responsive or non-responsive de-interleaving and/or addressing tags may be used in conjunction with other functions described herein.

In one embodiment, the geographic locations of all objects 404, certain categories of objects 404, or a single specific object 404 may be identified using a return signal from the tag 402 associated with the object 404. The location of the tag 402 and its associated object 404 may be determined by illuminating the tag 402 and receiving return signals at two or more receivers 408 each having a known location. For two or more return signals from the same tag 402, the difference in arrival time or received power (e.g., voltage standing wave ratio or VSWR) may be used to triangulate the location of the tag 402. This analysis may be repeated for return signals received from multiple tags 402. In addition, de-interleaving techniques may be applied to ignore or turn off the return signal from the tag 402 at the determined location. Further, to limit the number of tags 402 that respond during location analysis, addressing may be used to control the one or more tags 402 that transmit return signals.

Location determination techniques, such as the triangulation techniques described above, may be used in conjunction with various functions. For example, with reference to the exemplary depiction of location 424b, an overall identification of object 404 in a particular region can be made. For example, there may be a read zone 446 that serves as a designated interrogation zone through which items for purchase pass before exiting the locus 424 b. All objects 404 in the dedicated read zone 446 can be detected by analyzing return signals from tags 402 located in the read zone 446. Thus, a group of objects can move through the read band 446, being collectively identified and registered by the computer system 418. Subsequently, a transaction may be completed to purchase the item. This method of global object identification may be applied in other situations, such as identifying all items moving through a discharge dock, identifying all items on a truck or railcar as it moves through a predefined area, and the like.

As another example, the geographic location may be used to detect unauthorized movement of the object 404 (e.g., theft of the object 404). In one embodiment, this detection may be made if it is determined that the object 404 is in a location where it should not be present (e.g., the location of the object 404 is detected outside the geographic region of the location 424). In another embodiment, this detection may be made if the object moves more than a threshold distance and is in an unauthorized direction from a predetermined point. Such techniques may detect objects moving away from a door and toward, for example, a parking lot. Once the detection of possible unauthorized movement is made, the detection can be cross-referenced against any legitimate reasons for movement, such as the purchase of the subject, the scheduled shipment of the subject to another location, and so forth. If there is no legitimate reason for the detection that has been made, security measures may be triggered. Security measures may include, but are not limited to, issuing a warning to a governing body (e.g., a manager or police at site 424), opening a security camera and recording video of the area surrounding the exit gate or station through which the subject passes, initiating a survey, and so forth.

In another embodiment of determining the geographic location of the object 404, the geographic location of the receiver 408 may be used as a proxy for the location of the object 404 that receives the associated tag return signal. For example, if the receiver 408 at the payment region 440 detects a return signal of the tag 402, the associated object 404 will be assumed to be at or near the payment region 440. In the event that more than one receiver 408 detects a return signal of the tag 402, then the location of the receiver 408 that detects the highest signal strength of the return signal may be used as a proxy for the location of the associated object. In some embodiments, the receiver 408 may be mobile, such as a receiver 408 mounted on a truck, boat, train, or other vehicle. In this case, the geographic location of the receiver 408, which acts as a proxy for the geographic location of the tag 402/object 404, may be determined using, for example, Global Positioning System (GPS) technology.

Any of the foregoing methods for determining the geographic location of the tag 402 may include determining the elevation of the tag 402 in addition to the geographic location (e.g., as expressed by the bi-directional coordinates). Furthermore, in some embodiments, it may be possible to refine the positioning of the tag 402 by diverting the guided surface wave so that the guided surface wave only illuminates the tag 402 in certain regions of the site 424 at a time (e.g., by outputting a guided surface wave that changes direction over time using a multi-beam guided surface wave generation method).

Storing objects in a facility (e.g., a warehouse, a distribution center, a store of a retail store, etc.) typically involves planning in detail where the objects will be placed so that they can be easily found when needed. Using the disclosed techniques for illuminating and geo-locating the tag 402, less planning may be used. Alternatively, the object 404 may be placed in any location that will accommodate the object 404. This location may be determined at the time of placement using one of the aforementioned methods for determining the geographic location of the tag 402 associated with the object 404. This location may be stored in a database by computer system 418 and used to facilitate retrieval of object 404 at a later time. Alternatively, the object 404 may be placed in a suitable location without determining or storing information about the location. When it is desired to find an object, one of the aforementioned methods for determining the geographic location of the tag 402 associated with the object 404 may be used to determine the location of the object 404.

In one embodiment, the movement of the object 404 may be tracked by periodically or continuously making a location determination of the geographic location of the tag 402 associated with the object 404. Movement tracking in this manner may be used for inventory planning, for monitoring theft or product shrinkage, and for various other purposes. In one embodiment, the tracking of multiple tags 402 may provide additional information. For example, if a person is associated with a first tag 402 and an object 404 is associated with a second tag 402 and the tags are found to move together, the following determination may be made: the person is moving the object or is associated with movement of the object (e.g., both moving together in a vehicle). The same analysis may be performed for tags associated with the vehicle 402 and tags associated with the object 404.

The tag 402 may be associated with a person in many ways and used for various purposes. In one embodiment, the tag 402 associated with a person may take the form of or be included in an object normally carried by the person, such as a tag 402 that is similar in form factor to a credit card or a tag 402 that is part of an electronic device (e.g., a mobile phone or a housing for a mobile phone). Once the tag 402 is associated with a person, identifying the tag and thus the person may be used for various purposes. For example, tags 402 associated with a person may be detected at payment area 440 in conjunction with detection of tags 402 associated with objects that the person intends to purchase. If a bank account, credit card, or other payment means is further associated with the purchaser's associated tag 402, payment for the object 404 may be made through the computer system 418 that staged the transaction using the payment means associated with the purchaser's associated tag 402.

In another embodiment, an employee at location 424 may be required to carry tag 402. Various functions may be implemented by the computer system 418 using location tracking of the object 404 and/or association of the object 404 with a person. Exemplary functions may include tracking task completion, tracking work performance, tracking man-hours, and monitoring objects stolen by employees 404.

2(F) macroscopic illumination of the label

The previous section describes the use of guided surface waves to illuminate tags 402 in a well-defined geographic area corresponding to a known location typically controlled by a party.

Another embodiment will be described in conjunction with fig. 25. In this embodiment, the guided surface waves may be used to illuminate the tags 402 on areas where multiple sites 424 may be present, on areas where multiple receivers 408 controlled by parties are present, and/or on areas where the tags 402 may travel by a vehicle (e.g., truck, car, airplane, train, ship, etc.). These regions may include any region, path along which the cargo is intended to travel, zip code, city, county, state or province, country, continent, or region that may or may not correspond to regulatory, governmental, or geographic boundaries as determined by the operator of the probe P. In one embodiment, guided surface waves may be generated to illuminate the tag 402 on the earth (i.e., the world). Due to the size of the tags 402 and receivers 408 relative to the size of some of the coverage areas, a single tag 402 and receiver 408 are not shown in FIG. 25 for simplicity of illustration.

Note that the probe P is not drawn to scale and can be positioned at almost any location on the planet, and the representative embodiment illustrated in fig. 25 encompasses a guided surface wave capable of illuminating the tag 402 on earth. However, the aspects described below will apply to smaller illumination areas.

The guided surface wave preferably has a known fixed frequency (e.g., a first frequency). One or more further probes P may be used to generate a guided surface wave illuminating the label in at least a region overlapping the region in which the label 402 is illuminated by the guided surface wave of the first frequency. The other guided surface waves may have a frequency different from the first frequency, and the function performed in connection with illuminating the tag 402 with the other guided surface waves may be the same as or similar to the function performed in connection with illuminating the tag 402 with the guided surface waves of the first frequency. Thus, illuminating the tag 402 over a relatively wide expanse will be described in the context of a single guided surface wave of a first frequency and further described in the context of a tag 402 that is operably compatible with (e.g., powered by and capable of transmitting a return signal upon power up) the first frequency. The operation of the other frequencies of the guided surface wave and the other frequency compatible tags may be performed in the same manner and in parallel with the operation of the first frequency of the guided surface wave and the first frequency compatible tags.

Generally, as the area over which the tag 402 can be powered by the guided surface wave at the first frequency increases, the first frequency will decrease.

An entity interested in guided surface waves using a first frequency and generated by the probe P to power the tag 402 may deploy a tag 402 compatible with the first frequency. Deploying the tag 402 may include, for example, physically associating a compatible tag 402 with each object 404 that the entity wishes to track, and registering the identity of the object 404 and associated tag identifier in an appropriate database at the computer system 418 (not shown to scale). Physically associating the tag 402 and the object 404 may include adhering or securing the tag 402 directly to the object 404, packaging for the object 404, or some other item held with (e.g., manually held by) the object 404. In other embodiments, tag 402 may be internal to object 404 or an integral part of object 404.

The entity may also deploy the receiver 408 in a strategic location in the region where the guided surface wave will illuminate the tag 402. In addition to or instead of deploying its own receiver, the entity may coordinate with another party that deploys the receiver. The other party may provide information (e.g., a tag identifier) present in the return signal detected by the receiver to the entity. The provision of information may be implemented via computer system 418 and may include processing data to make various determinations, such as route tracking. It will be further appreciated that there may be multiple computer systems 418 that process information from the return signals. For example, a computer system 418 or multiple computer systems 418 can be deployed to process information for multiple sites for each entity that uses guided surface waves of a first frequency to identify objects of interest.

It is expected that the wide area illumination of the tag 402 will yield many object recognition and tracking functions not currently possible with conventional RFID technology. Additionally, any operations performed when using a local probe P (e.g., as described in connection with the embodiment of fig. 24) may also be performed using a remote probe P as described in connection with fig. 25.

Similar to the operation described above, the tag 402 illuminated with the guided surface wave will respond to the identifier. The identifier may be a unique identifier that distinguishes the tag 402 from all other tags 402, such as an IPv6 address or identifier in another format. The guided surface wave of the first frequency has sufficient energy density over the covered area (which may be at most the entire planet) to illuminate all tags 402 within the covered area. Thus, the tag 402 may continuously repeat the radiation by transmitting its return signal, typically at a second frequency higher than the first frequency. Continuously repeating radiating the return signal may include repeating the return signal without or with a slight delay (e.g., up to five seconds in one embodiment, up to two seconds in another embodiment, up to one second in another embodiment, or up to 0.5 seconds in another embodiment) between the return signal transmissions. In some cases, the tag 402 may be programmed to respond at certain times, with a certain periodicity, or in response to a response command. In other cases, the tag 402 may be commanded to not respond for at least a specific period of time (e.g., during a read operation of a plurality of tags, the read operation uses a de-interleaving method to accurately identify a large number of tags).

In one embodiment, as long as the tag 402 is in the region illuminated by the guided surface wave of the first frequency, the tag 402 will "always" radiate its identifier (e.g., repeatedly radiating the identifier over and over again with little or no delay between each radiation cycle) and during the lifetime of the tag 402. Thus, the tag 402 may be tracked anywhere in the region illuminated by the guided surface wave of the first frequency, so long as the tag 402 is within the operating range of the receiver 408, which is configured to detect a return signal at the transmit frequency (e.g., the second frequency) of the tag 402. As previously described, the location (e.g., longitude and latitude) and elevation of the tag 402 may be determined, for example, using triangulation or by using the location of the receiver as a proxy for the location of the tag.

In an exemplary embodiment where the coverage area is the entire world, each compatible tag 402 can be tracked at any time anywhere on the planet until the tag 402 stops transmitting. The tag 402 may stop transmitting by disabling in response to a disable command, by the tag circuitry 414 failing, by becoming physically corrupted, etc. In a global embodiment, the guided surface wave is operable to illuminate the label 402 at a relatively high altitude (such as up to about 35,000 feet). Thus, a tag 402 carried by an aircraft may be tracked, provided that the receiver can detect a reply signal from the tag 402.

Receiver 408 may be located at any location where tag 402 identification is desired. A non-exhaustive list of possible locations for the receiver 408 includes manufacturing facilities, farms, warehouses, distribution centers that process internet orders or post orders, retail locations, restaurants, grocery stores, national ports of entry, harbors, airports, along roads, along railroad tracks, and in moving vehicles (e.g., cars, trucks, airplanes, boats, trains, forklifts, etc.).

The widespread deployment of the receiver 408 may allow for life tracking of the object 404 associated with the tag 402. The amount of tracking information collected may depend on, for example, the nature of the object 404 associated with the tag 402, the supply chain of interest, or the degree of interest of a person or entity having a relationship with the object. As an example, the object 404 may be associated with the label 402 at the time of manufacture or packaging in a factory in beijing, china, and then tracked while loaded on a truck and traveling to a seaport, track, china. The object 404 is then tracked as it is loaded onto the cargo container and as it is loaded onto the ship. The object 404 may be further tracked in a route by ship to a harbor in los angeles, california, usa. The unloading of cargo containers from ships and subsequent loading of objects 404 on trains can be tracked at seaports by receiving return signals from tags 402. The object 404 may be tracked during travel by a train that may carry the object to montreal, tennessee, usa, where the object is removed from the train and transported to a shelf at a distribution center for montreal. Orders for objects may be received by an operator of a distribution center from customers of boston, ma. At that point, the object 404 may be removed from the rack, placed in a shipping box, transported to a monte fiies sorting and distribution center of the package delivery shipper, where the box containing the object is ultimately loaded onto the aircraft. All of those events can also be tracked. The object may be tracked as the aircraft travels to boston. Subsequently tracked are events such as: the unloading of objects from an aircraft, the transportation of objects to a boston classification and distribution center of a package delivery shipper, the loading of objects on delivery trucks, and the final delivery to a customer workplace or residence. Later, the customer may take the item 404 to travel on a vacation trip in paris, france. Assuming that the associated tag 402 is not detached or discarded from the object, the object may again be detected prior to or during travel to paris.

It should be appreciated that the foregoing object lifecycle tracking examples describe representative supply chain scenarios. Objects tracked using tags 402 responsive to guided surface waves may enter and go through commerce in many other ways, but may still be tracked for various purposes. Those purposes include, for example, supply chain management, inventory management, detecting theft, estimating time of arrival at a location, and the like.

Detailed information about where an object has gone and/or the person or entity with which the object has interacted can be used in a variety of scenarios. As an example, the identity of the purchaser of the object may be determined along with the supplier of the object, the retail location (if available), and the payment method (e.g., including a specific credit card, if available). This information may be combined with other information about the buyer and analyzed in order to generate sales opportunities, automatically buffer the product for warranty, for tracking service/product update purposes, or for other reasons.

In one embodiment, the disclosed identification and tracking techniques may be used to track the origin of outbreaks of food infections. In this embodiment, a sick person may be polled to determine what the person consumes, when the person consumes those items, and the person's food source (e.g., a restaurant that consumes food or a grocery store that purchases food). Information for each infected person may be populated into the database and cross-referenced to determine which food items are most likely to cause the disease. Sometimes cross-referencing this information alone may not be sufficient to determine food containing pathogens, especially if the food is distributed across a wide area of a country or region. Using information gathered from tags 402 associated with objects in the food supply chain can be used to discover what food is ill, where these come from and where other potentially contaminated food is currently located in the distribution chain.

For this purpose, the tag 402 may be associated with the food item as early as possible in the food chain. For example, the tag 402 can be associated with a can of peanut butter or a box of multiple cans of peanut butter at a processing plant that manufactures the peanut butter and/or fills the cans. Products (e.g., fruits and vegetables) may be associated with the label 402 at the packaging facility of the grower or packaged product (e.g., typically by placing the product in a container or crate for dispensing, and in some embodiments, selling the product to a consumer). The location of the tag 402 may be tracked as described above. Subsequently, during an outbreak of a food infection, the information of the sick person may be cross-referenced against location tracking information in an attempt to identify correspondence between the sick person and food products from a group or category of suspected food products, food products having a final dispensing pattern at a location proximate to the sick person, or food products classified in some other manner. In this way, the identification of a suspected food product may be quickly identified. It is expected that suspect product identification can be performed faster than if conventional analysis were performed.

Once a suspected food product is identified, the food product may be recalled. The tracking information may use both downstream and upstream to facilitate product recalls and other remedial actions. For example, the site of introduction of the pathogen can be identified and the pathogen can be eradicated. In addition, the last detected location of food individuals that may be contaminated and/or subject to recall may be identified. If those items are still in the grocery store or restaurant, the grocery store or restaurant may be alerted and the food may be kept from sale or use. Further, for products purchased by consumers, records establishing associations between purchasers and tag objects may be used to identify specific purchasers of some items. In some embodiments, the return signals may be analyzed to identify the present location at which individuals were recalled, and action may be taken to recall those individuals from a restaurant, home, grocery store, or other location.

Another exemplary application is tracking items for service or product upgrades or recalls. An exemplary embodiment of a product recall in the case of an automobile will be described, but modifications to the method for the case of routine services involving product upgrades will be apparent without further explanation. In this embodiment, the probe P emits a guided surface wave that illuminates a tag P associated with the car. The receiver 408 is located along a road, parking area, lane of travel, or other location through which a car may pass. As the car passes one of the receivers 408, a return signal from the associated tag 402 will be received by the receiver 408. The tag identifier or vehicle data (e.g., Vehicle Identification Number (VIN)) associated with the tag identifier may be cross-referenced against a database that stores, by manufacturer and model, what automobiles have completed the necessary work to address product safety recalls. Data on completion of the recalled work may be obtained from the auto dealers and other service providers as the work progresses. If it is determined that the vehicle has completed the job, no further action may be taken. If it is determined that the vehicle has not completed the job, additional action may be taken. For example, data may be transmitted to the tag 402 via an encoded carrier message in a guided surface wave. The data may cause the tag 402 to interface with the electronic components of the vehicle to display a message to the driver that the product recall should be resolved. Other actions may include attempting to contact the owner of the vehicle or an executive authority by telephone, email, text or data message, regular mail, etc.

Another application may be to charge the driver or vehicle owner for toll road use. In this example, the receiver 408 may be located from the entrance and exit of the toll road or along the toll road. Upon receiving a return signal from the tag 402 associated with the vehicle or driver passing the receiver 408, appropriate charges may be made for an account or credit card previously associated with the driver or vehicle in the computer system 418.

In another embodiment, the return signal or lack thereof from the tag 402 may be used to identify counterfeit goods or to verify legitimate goods. In one exemplary method, each legitimate object is associated with a tag 402 having a unique identifier. At various times, the tag identifier may be checked against a database of tag identifiers known to be associated with legitimate goods. Exemplary times for inspecting the goods may include times for controlling the checkpoint through customs and times for transferring the property or deed (title) in the goods between parties (e.g., from manufacturer to importer, from importer to distributor, from distributor to merchant, from merchant to consumer). If there is a match between the received tag identifier and a known legitimate tag identifier, the goods may be passed through customs authorities or accepted by the receiving party. If no match exists or no tag 402 exists, the customs authority may confiscate the shipment and conduct a survey or the recipient may reject the shipment.

It is apparent from the foregoing example that the amount of data collected with respect to various objects 404 tracked will depend on the degree of interest in the objects 404 and the reason for tracking the objects 404. Beyond the extent of the tracking object 404, the associated tag 402 may be used for additional purposes. An example will be provided. In this example, data may be transferred to the tag 402 or a query or command may be transmitted to the tag 402. In these cases, the data, query, or command may be transmitted via a communication link between the tag 402 and the receiver 404, or may be encoded in a message that is addressed to the tag 402 and forms part of the guided surface wave (e.g., as an encoded carrier wave message).

In one embodiment, data other than the tag identifier may be stored by the tag 402. The stored data or selected components of the stored data may be transmitted as part of an automated return signal. In other cases, the stored data or selected components of the stored data may be transmitted in a signal in response to a query or command. The information stored by the tag 402 may change over time as appropriate to support the operational functionality. The stored data component may include, but is not limited to, a previously determined location (e.g., location history) where the tag 402 is present; an identifier of the receiver 408 receiving the return signal from the tag 402; the identity or location of the manufacturer, importer, distributor or owner of the object 404 associated with the tag 402; the time and date of manufacture, packaging, or other processing; association of one or more additional objects 404 with tag 402; customs clearance data; location, time and date and/or other details regarding certain events, such as crossing ports of entry, manufacturing, purchasing, purchase amount, etc.; a product expiration date; a version number or value; product functions; a website or other data store from which more product data, warranty information, statutory terms, or intellectual property coverage information is available; information about obtaining product support or ordering accessories or replacement parts; and the like.

In various embodiments, the guided surface wave will exist for a long period of time to illuminate the tag 402 over a large geographic area. At some point, the value of the return signal for certain products may no longer be of interest to one or more parties. For example, a purchaser of the object 404 may not wish to have the tag 402 of the object send a return signal due to privacy concerns. As another example, after consumption of the food, the label 402 associated with the packaging of the food is of little value. In such cases, it is possible to recycle the tag, destroy the tag, turn off the return signal feature of the tag, contact the tracking data system (e.g., computer system 418) and opt out of further tracking of the tag, or other actions that alter the operation of the tag, receiver, or computer system.

In one embodiment, the tag 402 may be responsive to guided surface waves of more than one frequency. For example, tag 402 may emit a first return signal in the presence of a guided surface wave of a first frequency generated by a first probe and cover a broad area as described in connection with fig. 25, and may emit a second return signal in the presence of a guided surface wave of a second frequency generated by a second probe and cover a localized area (e.g., an area corresponding to a particular site) as described in connection with fig. 24. The return signal of the broad-area guided surface wave in response to the first frequency may be at a frequency different from the frequency of the return signal of the local-area guided surface wave at the second frequency. In this manner, return signals may be distinguished and/or received by different receivers 408.

2(G) computer system

The computer system in various embodiments may be any suitable system, such as a personal computer, a server, or a distributed system (e.g., a "cloud" computing environment). With additional reference to FIG. 26, an exemplary computer system 418 is illustrated communicatively coupled to the receiver 408. If appropriate, the computer system 418 may communicate with multiple receivers 408. If applicable, the computer system 418 may be in operable communication with the one or more probes P to guide characteristics of the guided surface wave as the probe 300 generates the guided surface wave, and to control the probe 300 to include data or commands for transmission to the one or more tags 402 with the guided surface wave.

The computer system 418, along with the receiver 408, the probe P, and the tag 402, may implement the techniques described in this disclosure. As indicated, the computer system 418 communicates with the receiver 408 via any suitable communication medium 420. In addition to performing the operations described herein, the computer system 418 may be a central staging system or some other form of management platform for managing the logical association of the tags 402 with the objects 404.

The computer system 418 can be implemented as a computer-based system capable of executing computer applications (e.g., software programs) including label management functions 448 that, when executed, implement the functions of the computer system 418 described herein. The tag management function 448 and database 450 can be stored on a non-transitory computer readable medium, such as memory 452. Database 450 may be used to store various sets of information for implementing the functions described in this disclosure. The memory 452 may be a magnetic, optical, or electronic storage device (e.g., hard disk, optical disk, flash memory, etc.) and may include a number of devices, including volatile and nonvolatile memory elements. Thus, memory 452 can comprise, for example, Random Access Memory (RAM) for acting as a system memory, read-only memory (ROM), solid state drive, hard disk, optical disk (e.g., CD and DVD), magnetic tape, flash device, and/or other memory component in addition to the associated drive, player and/or reader for the memory component.

To perform logical operations, the computer system 418 may include one or more processors 454 for executing instructions that implement logical routines. Processor 454 and memory 452 may be coupled using a local interface 456. The local interface 456 may be, for example, a data bus, a network, or other subsystem with an accompanying control bus.

The computer system 418 may have various input/output (I/O) interfaces for operatively connecting to various peripheral devices. Computer system 418 also may have one or more communication interfaces 458. Communication interface 458 may include, for example, a modem and/or a network adapter. Communication interface 458 may allow computer system 418 to send and receive data signals to and from other computing devices, receiver 408 and probe P via communication medium 420. In particular, communication interface 458 may operatively connect computer system 418 to communication media 420.

The receiver 408 includes communication circuitry, such as radio circuitry 460 that receives return signals from the tag 402 and a communication interface 462 that establishes operative communication with other devices via the communication medium 420. The radio circuitry 460 may include one or more antennas and a radio receiver (or transceiver in the case where the receiver 408 transmits data or commands to the tag 402).

The overall functionality of the receiver 408 may be controlled by a control circuit 464 comprising, for example, a processing device for executing logical instructions. The receiver 408 may also include a memory 466 for storing data and logic instructions in the form of executable code. Memory 466 may be a non-transitory computer-readable medium, such as one or more of: buffers, flash memory, hard drives, removable media, volatile memory, non-volatile memory, Random Access Memory (RAM), or other suitable devices. In a typical arrangement, the memory 466 includes non-volatile memory for long-term data storage and volatile memory, which functions as system memory for the control circuit 464. Receiver 408 may include any other suitable components, such as, but not limited to, a display, a speaker, a microphone, a user interface (e.g., a keypad and/or touch-sensitive input), a motion sensor, a location determination component (e.g., a GPS receiver), and so forth.

3. Conclusion

Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments. Thus, any of the disclosed features may be combined or interchanged with any of the other features.

Further, while certain embodiments have been shown and described, it is understood that equivalents and modifications which fall within the scope of the appended claims will occur to others skilled in the art upon the reading and understanding of this specification.

Claims (20)

1. An object recognition system (400), comprising:

a guided surface waveguide probe (P) that generates a guided surface wave having a frequency-dependent illumination area (426) in which one or more object identification tags (402) are powered by the guided surface wave and outside of which other object identification tags are not powered by the guided surface wave; and

a receiver (408) at the illumination zone that receives return signals from the one or more object identification tags located in the illumination zone, the return signals being transmitted by the object identification tags as an automatic reply to be powered by the guided surface wave.

2. The system of claim 1, wherein the guided surface waveguide probe comprises a charge terminal elevated above a land boundary medium (203, 410) configured to generate at least one resulting field that synthesizes a composite brewster angle of incidence (Θ) with the land boundary medium_i,B) The incident wavefront.

3. The system of claim 1 or 2, wherein the shape of the illuminated area is controlled by generating the guided surface wave to vary as a function of direction.

4. The system of any of claims 1-3, wherein the guided surface waveguide probe is a first probe (Pa), the guided surface wave is a first guided surface wave and the illumination zone is a first illumination zone (426a), the first illumination zone being sized to not overlap an adjacent second illumination zone (426b), the second illumination zone being defined by a second guided surface wave generated by a second guided surface waveguide probe (Pb).

5. The system of claim 4, wherein the first guided surface wave and the second guided surface wave have the same nominal frequency.

6. The system of claim 4, wherein the first and second guided surface waves have different nominal frequencies.

7. The system of any of claims 4 to 6, wherein the illumination zones correspond to a first location (424a) and a second location (424b), respectively, each location having a respective known geographic region and a single entity that coordinates or controls movement of objects associated with the object identification tags within the location.

8. The system of any of claims 1 to 3, wherein the illumination zone corresponds to a site (424) having a known geographic region and a single entity that coordinates or controls movement of an object associated with the object identification tag within the site.

9. The system of any of claims 1-8, wherein the system further comprises a computer system (418) configured to manage an inventory of objects (404) for a site (424), each object associated with one tag and with the inventory managed according to a tag identifier in return signals respectively received from the tags.

10. The system of any of claims 1-9, wherein the system further comprises a computer system (418) configured to identify locations of objects (404), each object associated with one tag and with a location determined from return signals respectively received from the tags.

11. A method of identifying an object (404), comprising:

generating a guided surface wave with a guided surface waveguide probe (P), the guided surface wave having a frequency-dependent illumination area (426) in which one or more object identification tags (402) are powered by the guided surface wave and outside of which other object identification tags are not powered by the guided surface wave; and

receiving, with a receiver located at the irradiation zone, a return signal from the one or more object identification tags located in the irradiation zone, the return signal being transmitted by the object identification tags as an automated reply to be powered by the guided surface wave.

12. The method of claim 11, wherein the guided surface waveguide probe comprises a charge terminal elevated above a land boundary medium (203, 410) configured to generate at least one resulting field that synthesizes a composite brewster angle of incidence (Θ) with the land boundary medium_i,B) The incident wavefront.

13. The method of claim 11 or 12, wherein the shape of the illuminated area is controlled by generating the guided surface wave as a function of direction.

14. The method according to any of claims 11-13, wherein the guided surface waveguide probe is a first probe (Pa), the guided surface wave is a first guided surface wave and the illumination area is a first illumination area (426a), the size of the first illumination area being controlled not to overlap with an adjacent second illumination area (426b), the second illumination area being defined by a second guided surface wave generated by a second guided surface waveguide probe (Pb).

15. The method of claim 14, wherein the first and second guided surface waves have the same nominal frequency.

16. The method of claim 14, wherein the first and second guided surface waves have different nominal frequencies.

17. The method of any of claims 14 to 16, wherein the illumination zones correspond to a first location (424a) and a second location (424b), respectively, the locations each having a respective known geographic region and a single entity that coordinates or controls movement of objects associated with the object identification tags within the locations.

18. The method of any of claims 11 to 13, wherein the illumination zone corresponds to a site (424) having a known geographic region and a single entity that coordinates or controls movement of an object associated with the object identification tag within the site.

19. The method of any of claims 11 to 18, further comprising: managing, with a computer system (418), an inventory of objects (404) for a site (424), each object associated with the tag and one of the inventory managed according to a tag identifier in a return signal received from the tag.

20. The method of any of claims 11 to 19, further comprising: locations of objects (404) are identified with a computer system (418), each object being associated with the tag and one of the locations determined from return signals received from the tag.