HK1240405B - Multi-layered planar multi-band antenna - Google Patents

Description

Multi-layer planar multi-band antenna

This application is a divisional application of the invention patent application with the application date of August 30, 2012, the invention name of which is “Single-Sided Multi-Band Antenna” and the application number of which is 201280048627.3.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/530,902, filed September 2, 2011, U.S. Application No. 13/402,777, filed February 22, 2012, U.S. Application No. 13/402,806, filed February 22, 2012, and U.S. Application No. 13/402,817, filed February 22, 2012, the entire contents of which are incorporated herein by reference.

Technical Field

An embodiment provides a multi-band composite loop antenna (multi-band antenna). An embodiment of the multi-band antenna generates signals in two or more frequency bands, and the two or more frequency bands can be adjusted and tuned independently of each other. An embodiment of the multi-band antenna includes at least one electric field radiator and at least one monopole/dipole formed according to a magnetic ring. At a specific frequency, the at least one electric field radiator combined with the various parts of the magnetic ring resonates at a first frequency band and radiates an electric field. At another specific frequency, the at least one monopole combined with the various parts of the magnetic ring resonates at a second frequency band and radiates an electric field. The shape of the magnetic ring can be tuned to improve the radiation efficiency at a specific frequency band and enable multi-band operation of the antenna embodiment.

Background Art

The continuous reduction in size of modern telecommunication equipment has created a need for improved antenna designs. Known antennas in devices such as mobile/cellular phones offer one of the main limitations on performance and are almost always compromised in one way or another.

Specifically, the efficiency of an antenna can have a significant impact on the performance of a device. A more efficient antenna will radiate a greater proportion of the energy provided to it from a transmitter. Similarly, due to the inherent reciprocity of antennas, a more efficient antenna will convert more of the received signal into electrical energy for processing by the receiver.

To ensure maximum energy transfer between a transceiver (a device operating as both a transmitter and a receiver) and an antenna (in both receive and transmit modes), the impedances of the two should be matched in magnitude. Any mismatch between the two will result in suboptimal performance, where energy is reflected from the antenna back toward the transmitter during transmission. When operating as a receiver, suboptimal antenna performance results in lower received power than would otherwise be possible.

Well-known simple loop antennas are typically current-fed devices that primarily generate a magnetic (H) field. Because of this, they are generally unsuitable for use as transmitters. This is particularly true for small loop antennas (i.e., loop antennas smaller than a wavelength or having a diameter smaller than a wavelength). In contrast, voltage-fed antennas (such as dipoles) generate both an electric (E) field and an H field and can be used in both transmit and receive modes.

The amount of energy received by or transmitted from a loop antenna is determined in part by its area. Typically, every time the area of the loop is halved, the amount of energy that can be received/transmitted decreases by about 3dB, depending on the application parameters (e.g., initial size, frequency, etc.). This physical constraint often means that very small loop antennas cannot be used in practice.

Composite antennas are those in which both transverse magnetic (TM) and transverse electric (TE) modes are excited to achieve higher performance benefits such as higher bandwidth (lower Q), greater radiation intensity/power/gain, and higher efficiency.

In the late 1940s, Wheeler and Chu first examined the properties of electrically small (ELS) antennas. Through their work, numerous numerical formulas were developed to describe the limitations of antennas as their physical size decreases. One particularly important limitation of ELS antennas noted by Wheeler and Chu is their large radiation quality factor (Q), meaning that, over an average time period, they store more energy than they radiate. According to Wheeler and Chu, ELS antennas have a high radiation Q, which results in minimal resistive losses in the antenna or matching network and very low radiation efficiency, typically between 1% and 50%. As a result, since the late 1940s, it has been widely accepted in the scientific community that ELS antennas have narrow bandwidth and poor radiation efficiency. Many of the modern achievements in wireless communication systems using ELS antennas have resulted from rigorous experimentation and optimization of modulation schemes and over-the-air protocols, but today's commercially available ELS antennas still exhibit the narrow bandwidth and low efficiency properties first identified by Wheeler and Chu.

In the early 1990s, Dale M. Grimes and Craig A. Grimes claimed to have mathematically established certain combinations of TM and TE modes operating together in ELS antennas that exceeded the low-radiation Q limit determined by Wheeler and Chu's theory. Grimes and Grimes described their work in a May 1995 paper titled "Bandwidth and Q of Antennas Radiating TE and TM Modes" published in the IEEE Transactions on Electromagnetic Compatibility. These claims sparked much debate and led to the term "composite field antenna," in which both TM and TE modes are activated, as opposed to "simple field antennas," in which either TM or TE modes are activated individually. The benefits of composite field antennas have been mathematically demonstrated by several well-respected RF experts, including those employed by the U.S. Naval Air Warfare Center Weapons Distribution, where they provided evidence of radiated Q below the Wheeler-Chu limit, improved radiation intensity, directivity (gain), radiated power, and radiation efficiency (P.L. Overfelft, D.R. Bowling, D.J. White, "Colocated Magnetic Loop, Electric Dipole Array Antenna (Preliminary Results)," Interim rept., September 1994).

Composite field antennas have proven to be complex and difficult to physically realize due to the adverse effects of element coupling and the associated difficulties in designing low-loss passive networks to combine electric and magnetic radiators.

There are many examples of two-dimensional, non-composite antennas, typically consisting of printed metal strips on a circuit board. However, these antennas are voltage-fed. One example of such an antenna is the Planar Inverted F Antenna (PIFA). Most similar antenna designs also primarily consist of quarter-wavelength (or multiples of a quarter-wavelength), voltage-fed, dipole antennas.

Planar antennas are also well known in the art. For example, U.S. Patent No. 5,061,938, issued to Zahn et al., requires an expensive polytetrafluoroethylene substrate or similar material for antenna operation. U.S. Patent No. 5,376,942, issued to Shiga, teaches a planar antenna that can receive but not transmit microwave signals. The Shiga antenna also requires an expensive semiconductor substrate. U.S. Patent No. 6,677,901, issued to Nalbandian, relates to a planar antenna that requires a substrate with a dielectric constant of 1:1 to 1:3 in a permeability ratio and can only operate within the HF and VHF frequency ranges (3 to 30 MHz and 30 to 300 MHz). Although it is known to print some lower frequency devices on inexpensive glass fiber reinforced epoxy resin laminates (e.g., FR-4) commonly used in ordinary printed circuit boards, the dielectric loss in FR-4 is considered too high, and the dielectric constant is not tightly controlled enough for such substrates used at microwave frequencies. For these reasons, alumina substrates are more commonly used. In addition, none of these planar antennas is a composite loop antenna.

The basis for the improved performance of composite field antennas in terms of bandwidth, frequency, gain, and radiation intensity stems from the effect of energy stored in the antenna's near field. In RF antenna design, it is desirable to convert as much energy as possible supplied to the antenna into radiated power. The energy stored in the antenna's near field has historically been referred to as reactive power and is used to limit the amount of power that can be radiated. When discussing complex power, there is a real part and an imaginary (often referred to as "reactive") part. Real power leaves the source and does not return, whereas imaginary power, or reactive power, tends to oscillate around a fixed position (within half a wavelength) of the source and interact with the source, affecting the operation of the antenna. Real power appearing from multiple sources is directly additive, while multiple sources of imaginary power can be additive or subtractive (cancelling). The benefit of composite antennas is that they are driven by both TM (electric dipole) and TE (magnetic dipole) sources, which enables engineers to create designs that use reactive cancellation previously unavailable in simple field antennas, thereby improving the antenna's real power transfer characteristics.

In order to be able to eliminate reactive power in a composite antenna, it is necessary that the electric field and the magnetic field operate orthogonally to each other. Although many arrangements of the electric field radiators necessary for emitting the electric field and the magnetic rings necessary for generating the magnetic field have been proposed, all such designs have always been based on three-dimensional antenna solutions. For example, U.S. Patent 7,215,292 granted to McLean requires a pair of magnetic rings in parallel planes, wherein an electric dipole on a third parallel plane is located between the paired magnetic rings. U.S. Patent 6,437,750 granted to Grimes et al. requires two pairs of magnetic rings and electric dipoles to be physically arranged to be orthogonal to each other. U.S. Patent Application US2007/0080878 filed by McLean teaches an arrangement in which the magnetic dipoles and electric dipoles are also in orthogonal planes.

Commonly owned U.S. patent application Ser. No. 12/878,016 teaches a linearly polarized, multi-layer planar composite loop antenna. Commonly owned U.S. patent application Ser. No. 12/878,018 teaches a linearly polarized, single-sided composite loop antenna. Finally, commonly owned U.S. patent application Ser. No. 12/878,020 teaches a linearly polarized, self-contained composite loop antenna. These commonly owned patent applications differ from existing antennas in that they are composite loop antennas having one or more magnetic loops and one or more electric field radiators physically arranged in two dimensions, rather than requiring a three-dimensional arrangement of magnetic loops and electric field radiators as in the antenna designs of McLean and Grimes et al.

Summary of the Invention

According to the present disclosure, a multi-layer planar multi-band antenna is provided, comprising: a magnetic ring located on a first plane and configured to generate a magnetic field, the magnetic ring forming two or more horizontal segments and two or more vertical segments, the two or more horizontal segments and the two or more vertical segments forming a substantially 90-degree angle therebetween, a first horizontal segment of the two or more horizontal segments emitting a first electric field in a low frequency band, and a second horizontal segment of the two or more horizontal segments emitting a second electric field in a high frequency band, wherein the magnetic ring has a first inductive reactance that adds to the total inductive reactance of the multi-band antenna; and a parasitic electric field radiator located below the first plane. on a second plane of the multi-band antenna, at least half of the parasitic electric field radiator is located at the following position on the second plane: if the position is on the first plane, the position will cause the parasitic electric field radiator to be placed within the magnetic ring, the parasitic electric field radiator is not coupled to the magnetic ring, the parasitic electric field radiator is configured to emit a third electric field in the low frequency band, the third electric field strengthens the first electric field and is orthogonal to the magnetic field, wherein the parasitic electric field radiator has a first capacitive reactance that adds to the total capacitive reactance of the multi-band antenna, wherein the physical arrangement between the parasitic electric field radiator and the magnetic ring results in a second capacitive reactance that adds to the total capacitive reactance, and wherein the total inductive reactance is substantially matched to the total capacitive reactance.

BRIEF DESCRIPTION OF THE DRAWINGS

1A is a plan view of a single-sided 2.4 GHz (gigahertz) self-contained, circularly polarized, composite loop antenna according to an embodiment;

FIG1B shows the 2.4 GHz antenna of FIG1A , wherein right-handed circularly polarized signals propagate along the positive z-direction and left-handed circularly polarized signals propagate along the negative z-direction;

2A is a plan view of a single-sided 402 MHz self-contained, circularly polarized, composite loop antenna having two electric field radiators positioned along two points of minimum reflected current, according to an embodiment;

FIG2B is a graph showing the return loss of the single-sided 402 MHz antenna of FIG2A ;

FIG3 is a plan view of an embodiment of a single-sided 402 MHz self-contained, circularly polarized, composite loop antenna using dual delay loops;

FIG4 is a plan view of one side of an embodiment of a dual-sided 402 MHz self-contained, circularly polarized, composite loop antenna that utilizes one electric field radiator and a patch on the back side of the antenna that serves as a second electric field radiator;

FIG5 is a plan view of one side of an embodiment of a dual-sided 402 MHz self-contained, circularly polarized, composite loop antenna using one E-field radiator, a patch on the back side of the antenna that serves as a second E-field radiator, and a combination of delay loops and stubs;

FIG6 is a plan view of one side of an embodiment of a dual-sided 402 MHz self-contained, circularly polarized, composite loop antenna that uses three stubs to adjust the delay between an E-field radiator and a backside patch on the backside of the antenna that serves as a second E-field radiator;

FIG7 is a plan view of one side of an embodiment of a dual-sided 402 MHz self-contained, circularly polarized, composite loop antenna having an E-field radiator with orthogonal traces for electrically extending the E-field radiator, a backside patch on the backside of the antenna serving as a second E-field radiator, a substantially arcuate delay ring, and a stub;

8A is a plan view of an embodiment of a double-sided 700 MHz to 2100 MHz multi-band antenna showing a parasitic radiator and a capacitive patch on the back plane of the antenna;

8B is a plan view of the multi-band antenna shown in FIG. 8A , further illustrating a magnetic loop formed in the multi-band antenna;

9A is a plan view of an embodiment of a 2.4 GHz/5.8 GHz multi-band antenna having an electric field radiator and a monopole formed from a magnetic loop to generate two frequency bands;

FIG9B shows the return loss of the 2.4 GHz/5.8 GHz multi-band antenna of FIG9A ;

10 is a plan view of an embodiment of a 2.4 GHz/5.8 GHz multi-band antenna having an electric field radiator and a dipole formed from a magnetic loop to generate two frequency bands;

11A and 11B are plan views of the top and bottom planes of an embodiment of a primary LTE antenna;

FIG12 illustrates an embodiment of a 2.4 GHz/5.8 GHz single-sided, multi-band CPL antenna having a substantially curvilinear trace extending downward from the left side of the radiator and a rectangular brick extending downward from the first arm of the magnetic loop; and

13 shows an alternative embodiment of a 2.4 GHz/5.8 GHz single-sided, multi-band CPL antenna having a substantially curvilinear trace extending downward from the left side of the radiator and a rectangular brick extending upward from the first arm of the magnetic loop.

DETAILED DESCRIPTION

Embodiments provide a single-sided, multi-layer circularly polarized, self-contained, composite loop antenna (circularly polarized CPL antenna). Embodiments of the circularly polarized CPL antenna generate a circularly polarized signal by using two electric field radiators that are physically oriented orthogonally to each other, and by ensuring that the two electric field radiators are positioned such that the electrical delay between the two electric field radiators causes the two electric field radiators to emit their respective electric fields out of phase. Ensuring appropriate electrical delay between the two electric field radiators also maintains high antenna efficiency and improves the antenna's axial ratio.

Single-sided composite loop antennas, multi-layer composite loop antennas, and self-contained composite loop antennas are discussed in U.S. Patent Application Nos. 12/878,016, 12/878,018, and 12/878,020, the entire contents of which are incorporated herein by reference.

Circular polarization refers to a phenomenon in which the electric and magnetic fields of an electromagnetic wave generated by an antenna rotate while maintaining their orthogonality as it propagates through space. Circular polarization can penetrate moisture and obstacles better than linear polarization. This makes it suitable for humid environments, urban areas with many buildings and trees, and satellite applications.

For linearly polarized antennas, the transmitter and receiver of a separate device must have similar orientations to enable the receiver to receive the strongest signal from the transmitter. For example, if the transmitter is oriented vertically, the receiver should also be oriented vertically to receive the strongest signal. On the other hand, if the transmitter is oriented vertically, but the receiver is slightly tilted or tilted at an angle rather than vertical, a weaker signal will be received. Similarly, if the transmitter is tilted at an angle and the receiver is vertical, the receiver will receive a weaker signal. This is a significant problem for certain types of mobile devices, such as cellular phones, where the receiver in the phone may have a constantly changing orientation, or where the orientation of the phone with the best signal strength is also the least comfortable for the user. Therefore, when designing antennas for portable electronic devices or satellite receivers, the orientation of the receiving device cannot be predicted, which leads to reduced receiver performance. In the case of portable electronic devices, the orientation of the receiver inevitably changes unpredictably depending on what the user is doing while using the portable electronic device.

A possible solution to this problem is to use multiple receivers or multiple transmitters arranged in different orientations, thereby improving the quality of the signal received by the receivers. For example, the first receiver could be vertical, the second receiver could be oriented at a 45-degree angle, and the third receiver could be horizontal. This would enable the receiver to receive linear vertically polarized signals, linear horizontally polarized signals, and linearly polarized signals at certain angles. In this case, when the signal transmitted from the transmitter matches the orientation of one of the receivers, the receiver will receive the strongest signal. However, using multiple receivers/transmitters requires larger receiving/transmitting equipment to accommodate the multiple receivers/transmitters. In addition, the power consumption required to operate the additional receivers/transmitters offsets the benefits of multiple receivers/transmitters.

In circular polarization, the transmitter and receiver do not need to be similarly oriented as the propagated signal continuously rotates on its own. Therefore, the receiver will receive the same signal strength regardless of its orientation. As noted, in circular polarization, the electric and magnetic fields continuously rotate while maintaining their respective orthogonality as they propagate through space.

FIG1A shows an embodiment of a single-sided, 2.4 GHz, circularly polarized CPL antenna 100 having a length of approximately 2.92 cm and a height of approximately 2.92 cm. Although specific dimensions are indicated for this antenna design and other embodiments disclosed herein, it should be understood that the present invention is not limited to a specific size or operating frequency, and antennas using different sizes, frequencies, components, and operating characteristics may be developed without departing from the teachings of the present invention.

Antenna 100 includes a magnetic loop 102, a first electric field radiator 104 directly coupled to the magnetic loop 102, and a second electric field radiator 106 orthogonal to the first electric field radiator 104. Both electric field radiators 104 and 106 are physically located inside the magnetic loop 102. Although electric field radiators 104 and 106 can also be located outside the magnetic loop, it is preferred that electric field radiators 104 and 106 be located inside the magnetic loop to maximize antenna performance. Both first electric field radiator 104 and second electric field radiator 106 are quarter-wavelength monopoles, but alternative embodiments may use monopoles that are some multiple of a quarter wavelength.

Composite loop antennas can operate in both transmit and receive modes, achieving higher performance than conventional loop antennas. The two main components of a CPL antenna are a magnetic loop that generates a magnetic field (H field) and an E-field radiator that emits an electric field (E field). The H and E fields must be orthogonal to each other for the electromagnetic waves emitted by the antenna to propagate efficiently through space. To achieve this, the E-field radiator is positioned at approximately 90 electrical degrees or approximately 270 electrical degrees along the magnetic loop. Orthogonality between the H and E fields can also be achieved by positioning the E-field radiator at a point along the magnetic loop where the current flowing through the loop is at its lowest reflection. The point along the CPL antenna's magnetic loop where the current is at its lowest reflection depends on the loop's geometry. For example, the point where the current is at its lowest reflection can be initially determined as the first region of the magnetic loop. By adding or removing metal from the magnetic loop to achieve impedance matching, the point where the current is at its lowest reflection can be shifted from the first region to the second region.

Returning to FIG. 1A , electric field radiators 104 and 106 can be coupled to magnetic ring 102 at the same 90-degree or 270-degree connection point, or at the same connection point where the current flowing through magnetic ring 102 is at a minimum reflection. Alternatively, the first electric field radiator can be positioned at a first point along the magnetic ring where the current is at a minimum reflection, and the second electric field radiator can be positioned at a different point along the magnetic ring where the current is also at a minimum reflection. The electric field radiators do not need to be directly coupled to the magnetic ring. Alternatively, each of the electric field radiators can be connected to magnetic ring 102 using a narrow electrical trace to increase inductive delay. In particular, when the electric field radiators are located within the magnetic ring, care must be taken to ensure that the radiators do not electrically couple with other parts of the antenna (e.g., transition portion 108 or counterpoise 110, described further below), which could disrupt the performance or operability of the antenna unless some form of coupling (as described further below) is desired.

As indicated, antenna 100 includes a transition portion 108 and a counterpoise 110 for first and second electric field radiators 104 and 106. Transition portion 108 comprises a portion of magnetic ring 102 having a width greater than the width of magnetic ring 102. The function of transition portion 108 will be described further below. The built-in counterpoise 110 enables antenna 100 to be completely independent of any ground plane or chassis of the product in which the antenna is used. Embodiments of antenna 100, and similar alternative embodiments of circularly polarized CPL antennas, do not necessarily include a transition portion and/or a counterpoise.

The transition section partially delays the voltage distribution around the magnetic ring and sets the impedance of the counterpoise so that the voltage appearing in the magnetic ring and the transition section does not cancel the voltage being emitted by the electric field radiator. When the counterpoise and the electric field radiator are positioned 180 degrees out of phase with each other in the antenna, the antenna gain can be improved regardless of any nearby ground plane. It should also be understood that the length and width of the transition section can be adjusted to match the voltage appearing in the counterpoise.

Antenna 100 may also include a balun 112. A balun is an electrical transformer that converts an electrical signal balanced about ground (differential) into an unbalanced (single-ended) signal, or vice versa. Specifically, a balun presents a high impedance to common-mode signals and a low impedance to differential-mode signals. Balun 112 is used to eliminate common-mode currents. Additionally, balun 112 tunes antenna 100 to a desired input impedance and adjusts the impedance of the entire magnetic ring 102. Balun 112 is substantially triangular in shape and includes two sections separated by a central gap 114. Alternative embodiments of antenna 100, and similarly, alternative embodiments of self-contained CPL antennas and circularly polarized CPL antennas, do not necessarily include a balun.

The length of transition section 108 can be set based on the operating frequency of the antenna. For higher frequency antennas, where the wavelength is shorter, a shorter transition section can be used. On the other hand, for lower frequency antennas, where the wavelength is longer, a longer transition section 108 can be used. Transition section 108 can be adjusted independently of counterpoise 110.

The counterpoise 110 is said to be internal because it is formed by the magnetic ring 102. Therefore, the self-contained counterpoise antenna does not require the device using the antenna to provide a ground plane. The length of the counterpoise 110 can be adjusted as needed to obtain the desired antenna performance.

In the case of a simple, quarter-wavelength monopole, the ground plane and the countersunk are one and the same. However, the ground plane and the countersunk do not necessarily need to be the same. The ground plane is where the reference phase point is located, while the countersunk is what sets the far-field polarization. In the case of a self-contained CPL antenna, the transition is used to create a 180-degree phase delay relative to the countersunk. It also moves the reference phase point relative to ground into the countersunk, making the antenna independent of the device to which it is connected. When a balun is included at the end of the magnetic loop, both ends of the magnetic loop serve as the ground for the antenna. If the antenna does not include a balun, the portion of the magnetic loop approximately 180 degrees from the electric field radiator will still act as the ground plane.

Embodiments of antenna 100 are not limited to including transition portion 108 and/or counterpoise 110. Thus, antenna 100 may not include transition portion 108 but still include counterpoise 110. Alternatively, antenna 100 may not include transition portion 108 or counterpoise 110. If antenna 100 does not include counterpoise 110, the gain and efficiency of antenna 100 will be slightly reduced. If antenna 100 does not include a counterpoise, the electric field radiator will still seek a counterpoise, such as a metal sheet, approximately 180 degrees from the electric field radiator (e.g., to the left of magnetic ring 102 in FIG. 1A ). While the left side of magnetic ring 102 (without a counterpoise) can function in a similar manner, it will not be as effective as including a counterpoise 110 having a width greater than that of magnetic ring 102 (due to its reduced width). In other words, any component connected to the point of minimum reflected current along the magnetic ring will seek a counterpoise 180 degrees from that point of minimum reflected current. In antenna 100, counterpoise 110 is positioned approximately 180 degrees from the point of minimum reflected current for electric field radiators 104 and 106. However, as noted above, despite the benefits of counterpoise 110, removing it has only a marginal effect on the gain and performance of antenna 100.

Although Figure 1A shows a plan view of the antenna 100 having a horizontally oriented first electric field radiator and a vertically oriented second electric field radiator, in some embodiments, the electric field radiators can be oriented at different angles along the same plane. Although the precise position of the two electric field radiators can be changed, it is important that the two electric field radiators are positioned orthogonal to each other so that the antenna 100 operates as a circularly polarized CPL antenna. For example, the first electric field radiator can be tilted at a 45-degree angle, where the electrical trace couples the tilted first electric field radiator to the magnetic ring. The second electric field radiator only needs to be orthogonal to the first electric field radiator to enable the antenna to produce a circularly polarized signal. In such an embodiment, the substantially cross shape formed by the two intersecting electric field radiators will be tilted 45 degrees.

Circularly polarized CPL antenna 100 is planar. Thus, right-hand circular polarization (RHCP) is transmitted in a first direction, perpendicular to the plane formed by antenna 100 and along the positive z-direction. Left-hand circular polarization (LHCP) is transmitted in a second direction, opposite to the first direction and along the negative z-direction. FIG. 1B shows RHCP 120 radiating from the front face of antenna 100 and LHCP 122 radiating from the back face of antenna 100.

At lower frequencies, if there's insufficient delay between the first and second electric field radiators, the second electric field radiator, arranged orthogonally to the second electric field, may be ineffective. Without sufficient delay between the two electric field radiators, they may emit their respective electric fields simultaneously or may emit electric fields that are insufficiently out of phase, resulting in cancellation of their electric fields. This electric field cancellation results in lower antenna efficiency and gain because less of the electric field is emitted into space. It may also result in a cross-polarized antenna rather than a circularly polarized antenna.

As a solution, referring back to FIG. 1A , the two electric field radiators can be positioned at different points along the magnetic loop. Thus, the second electric field radiator 106 does not have to be positioned on top of the first electric field radiator 104. For example, one of the electric field radiators can be positioned at a 90-degree phase point, while the second electric field radiator can be positioned at a 270-degree phase point. As noted above, the magnetic loop in a CPL antenna can have multiple points along the loop where the current is at a minimum reflection. One of the electric field radiators can then be positioned at a first point where the current is at a minimum reflection, while the second electric field radiator can be positioned at a second point where the current is also at a minimum reflection.

In the antenna 100 of FIG1A , both the electric field radiators 104 and 106 are connected at the same point of reflection minimum. However, as shown in FIG2A , in an alternative embodiment of the antenna 100, the first electric field radiator 104 can be connected to a first point along the magnetic loop 102, while the second electric field radiator 106 can be connected to a second point along the magnetic loop 102. However, as also shown in FIG2A , as noted, the two electric field radiators, even if not physically in contact with each other, still need to be positioned orthogonally relative to each other for the antenna to have circular polarization.

1A , the distance 105 between the first electric field radiator 104 and the second electric field radiator 106 is long enough to ensure that the first electric field radiator 104 is out of phase with the second electric field radiator 106. In the antenna 100 , the center point 107 is the feed point of the second electric field radiator.

In antenna 100 , current flows into antenna 100 along magnetic ring 102 via the right half of balun 112 , flows into first electric field radiator 104 , flows into first electric field radiator 106 , flows through transition portion 108 , flows through counterpoise 110 , and flows out through the left half of balun 112 .

FIG2A illustrates an embodiment of a single-sided, 402 MHz, self-contained, circularly polarized CPL antenna 200. Antenna 200 includes two electric field radiators 204 and 206 positioned along two different reflection minima. 402 MHz antenna 200 has a length of approximately 15 cm and a height of approximately 15 cm. Antenna 200 does not include a transition portion, but does include a counterpoise 208. Counterpoise 208 spans the length of the left side of magnetic ring 202 and has a width that is twice the width of magnetic ring 202. However, these dimensions are not fixed, and the counterpoise length and width can be tuned to maximize antenna gain and performance. Antenna 200 also includes a balun 210, although alternative embodiments of antenna 200 do not necessarily include it. In antenna 200, balun 210 is physically located inside magnetic ring 202. However, balun 210 can also be physically located outside magnetic ring 202.

In antenna 200, current flows into antenna 200 at feed point 216 via the right half of balun 210. The current then flows to the right along magnetic ring 202. First electric field radiator 204 is positioned along the bottom half of magnetic ring 202, to the right of balun 210. Current flows into first electric field radiator 204 and flows along the entire length of first electric field radiator 204, continues along magnetic ring 202, and flows through delay ring 212. Current then flows through the entire length of second electric field radiator 206 and continues through the top side of magnetic ring 202, flows through counterpoise 208, and flows into delay stub 214, and so on.

As shown, antenna 200 includes a first delay ring 212 protruding into magnetic ring 202. Delay ring 212 is used to adjust the delay between first electric field radiator 204 and second electric field radiator 206. First electric field radiator 204 is positioned at a 90-degree phase point, while second electric field radiator 206 is positioned at a 180-degree phase point. The widths of both electric field radiators 204 and 206 are identical. The widths and lengths of both electric field radiators 204 and 206 can be varied to tune the antenna's operating frequency and adjust the antenna's axial ratio.

The axial ratio is the ratio of the orthogonal components of the electric field. A circularly polarized field consists of two orthogonal electric field components of equal amplitude. For example, if the amplitudes of the electric field components are unequal or nearly equal, the result is an elliptically polarized field. The axial ratio is calculated by taking the logarithm of a first electric field along a first direction divided by a second electric field orthogonal to the first. In circularly polarized antennas, it is desirable to minimize the axial ratio.

The length and width of the delay loop 212 and the thickness of the traces comprising the delay loop 212 can be tuned as needed to achieve the necessary delay between the two electric field radiators. The delay loop 212 is made to protrude into the magnetic ring 202 (i.e., positioned inside the magnetic ring 202) to optimize the axial ratio of the antenna 200. However, the delay loop 212 can also protrude outside the magnetic ring 202. In other words, the delay loop 212 increases the electrical length between the first electric field radiator 204 and the second electric field radiator 206. The delay loop 212 does not need to be substantially rectangular in shape. The delay loop 212 can be implemented as a curved, sawtooth, or any other shape that will significantly slow the flow of electrons along the delay loop 212, thereby ensuring that the electric field radiators are out of phase with each other.

One or more delay loops may be added to the antenna to achieve the appropriate delay between the two electric field radiators. For example, FIG2A shows an antenna 200 having a single delay loop 212. However, in addition to having a single delay loop 212, alternative embodiments of the antenna 200 may have two or more delay loops.

Antenna 200 also includes a stub 214 on the left side of magnetic ring 202. Stub 214 is directly coupled to magnetic ring 202. Stub 214 capacitively couples to second electric field radiator 206, thereby electrically extending electric field radiator 206 to tune the impedance matching to a certain wavelength band. In antenna 200, second electric field radiator 206 cannot be physically made longer because extending electric field radiator 206 in this manner would capacitively couple electric field radiator 206 to counterpoise 208, thereby degrading antenna performance.

As noted above, as shown in FIG2A , the second electric field radiator 206 normally needs to be longer than its length shown in FIG2A . Specifically, the second electric field radiator 206 would have to be lengthened by approximately the length of the stub 214 . However, by making the electric field radiator 206 longer, it would capacitively couple to the left side of the magnetic ring 202 . The use of the stub enables the second electric field radiator to appear electrically longer. The electrical length of the electric field radiator 206 can be tuned by moving the stub 214 up and down along the left side of the magnetic ring 202 . Moving the stub 214 higher along the left side of the magnetic ring 202 results in the electric field radiator 206 being electrically longer. On the other hand, moving the stub 214 lower along the left side of the magnetic ring 202 results in the electric field radiator 206 being electrically shorter. The electrical length of the electric field radiator 206 can also be tuned by changing the physical size of the stub 214 .

Figure 2B is a graph showing the return loss of antenna 200 without stub 214. Figure 2B illustrates the return loss of antenna 200, which includes two electric field radiators with different electrical lengths. When the two electric field radiators have different electrical lengths, the return loss exhibits two dips at different frequencies. A first dip 220 and a second dip 222 correspond to the frequencies at which the antenna's impedance matches. Each electric field radiator generates its own resonance. In terms of return loss, each resonance generates multiple dips. In antenna 200, because first electric field radiator 204 is closer to feed point 216 along magnetic ring 202, it generates a slightly higher resonance than second electric field radiator 206. This slightly higher resonance corresponds to the second dip. On the other hand, due to the longer length between feed point 216 and second electric field radiator 206, second electric field radiator 206 generates a lower resonance. This lower resonance corresponds to first dip 220. As mentioned above, the stub 214 electrically extends the second electric field radiator 206. This thereby moves the first dip 220 and aligns the first dip 220 with the second dip 222.

FIG3 is a plan view of a single-sided, 402 MHz, self-contained, circularly polarized antenna 300 with two delay loops. Antenna 300 has a length of approximately 15 cm and a height of approximately 15 cm. Antenna 300 includes a magnetic loop 302, a first electric field radiator 304 positioned along a first point where current reflection is minimized, and a second electric field radiator 306 positioned along a second point where current reflection is minimized. Antenna 300 also includes a counterpoise 308 and a balun 310. Compared to antenna 200 from FIG2A , antenna 300 does not include stub 214, but does include two delay loops: a first delay loop 312 along the right side of magnetic loop 302 and a second delay loop 314 along the left side of magnetic loop 302. Second delay loop 314 is used to adjust the electrical delay between the two electric field radiators 304 and 406. In antenna 300 , top portion 316 of second delay ring 314 is capacitively coupled to second electric field radiator 306 , which performs a similar function as stub 214 of antenna 200 by electrically extending second electric field radiator 306 .

When an antenna includes two or more delay loops, the two or more delay loops do not need to be the same size. For example, in antenna 300, first delay loop 312 is almost half the size of second delay loop 314. Alternatively, second delay loop 314 can be replaced by two smaller delay loops. Delay loops can be added to either side of the magnetic loop, and a single antenna can have delay loops on one or more sides of the magnetic loop.

Without the use of delay rings, an appropriate delay between the two electric field radiators can be achieved by increasing the overall length of the magnetic ring. Therefore, the magnetic ring 302 would need to be larger if it did not include delay rings 312 and 314 to ensure an appropriate delay between the first electric field radiator 304 and the second electric field radiator 306. Therefore, during antenna design, the use of delay rings can be used as a space-saving technique, that is, the overall size of the antenna can be reduced by moving various components to physical locations on the interior of the magnetic ring 302.

Figures 2A and 3 show examples of antennas with magnetic loops whose corners are cut at approximately 45-degree angles. Cutting the corners of the magnetic loop at an angle improves the efficiency of the antenna. Having corners of the magnetic loop that form an approximately 90-degree angle affects the flow of current through the loop. When the current flowing through the loop hits a 90-degree corner, it causes the current to rebound, with the reflected current either flowing against the main current or forming an eddy current pool. The energy loss caused by the 90-degree corners can negatively impact the performance of the antenna, particularly in smaller antenna embodiments. Cutting the corners of the magnetic loop at an approximately 45-degree angle improves the flow of current around the corners of the loop. Therefore, the angled corners reduce the obstruction of electrons in the current as they flow through the loop. Although cutting the corners at a 45-degree angle is preferred, alternative embodiments that cut at angles other than 45 degrees are also possible. Any CPL antenna can include a magnetic loop with angled corners, but cutting the corners is not always necessary.

Instead of using a loop to adjust the delay between two E-field radiators in an antenna, one or more substantially rectangular metal stubs can be used to adjust the delay between the two E-field radiators. FIG4 shows an embodiment of a double-sided (multi-layer), 402 MHz, self-contained, circularly polarized antenna 400. Antenna 400 includes a magnetic loop 402, a first E-field radiator 404 (vertical), a second E-field radiator 406 (horizontal), a transition portion 408, a counterpoise 410, and a balun 412.

The first electric field radiator 406 is attached to a square patch 414 that electrically extends the first electric field radiator 406. The square patch 414 is directly coupled to the magnetic loop 402. The size of the square patch 414 can be adjusted accordingly based on how the electric field radiator 406 is to be tuned. Antenna 400 also includes a backside patch 416 located on the back side of the substrate to which the antenna is applied. Specifically, backside patch 416 spans the entire length of the left side of the magnetic loop 402. Backside patch 416 radiates perpendicularly along with the first electric field radiator 404 and out of phase with the second electric field radiator 406. Backside patch 416 is not electrically connected to the magnetic loop and, as such, is a parasitic electric field radiator. Therefore, antenna 400 is an example of a circularly polarized CPL antenna having two vertical elements acting as electric field radiators and only one horizontal element acting as a first electric field radiator. Other embodiments may include many different combinations of vertical elements operating together and many different combinations of horizontal elements operating together, and as long as the vertical elements are out of phase with the horizontal elements as described herein, the antenna will be circularly polarized.

Antenna 400 also includes a first delay stub 418 and a second delay stub 420. The two delay stubs 418 and 420 are substantially rectangular in shape. Delay stubs 418 and 420 are used to adjust the delay between the first electric field radiator 404 and the second electric field radiator 406. Although FIG4 shows the two delay stubs 418 and 420 protruding into the magnetic ring 402, alternatively, the two delay stubs 418 and 420 can be arranged so that the two delay stubs 418 and 420 protrude outside the magnetic ring 402.

FIG5 illustrates another embodiment of a dual-sided, 402 MHz, self-contained, circularly polarized, CPL antenna 500. In contrast to other embodiments presented to date, antenna 500 includes a magnetic loop 502 and only one electric field radiator 504. Rather than using a secondary electric field radiator, antenna 500 utilizes a large metallic backside patch 506 on the back side of antenna 500 as a parasitic, perpendicular electric field radiator. Backside patch 506 has a substantially rectangular cutout 508 cut away from backside patch 506 to reduce capacitive coupling between electric field radiator 504 and backside patch 506. Cutout 508 does not affect the radiation pattern emitted by backside patch 506. Antenna 500 also includes a transition 510, a counterpoise 512, and a balun 514.

Specifically, antenna 500 shows the use of a combination of delay rings, delay stubs, and metal patches to adjust the delay between electric field radiator 504 and backside patch 506. Delay ring 516 does not radiate and is used to adjust the delay between electric field radiator 504 and backside patch 506. Delay ring 516 also has its corners cut at a certain angle. As mentioned above, cutting the corners at a certain angle can improve the flow of current around the corners.

Antenna 500 also includes a metal patch 518 directly coupled to magnetic loop 502 and a smaller delay stub 520 also coupled to magnetic loop 502. Both metal patch 518 and delay stub 520 help tune the delay between back patch 506, which acts as a vertical radiator, and electric field radiator 504. Metal patch 518 has its bottom left corner cut off to reduce capacitive coupling between metal patch 518 and delay loop 516.

The backside patch 506 (even though it is parasitic) is positioned in a direction orthogonal to the electric field radiator 504. For example, if the electric field radiator 504 is oriented at an angle and coupled to the magnetic ring 502 via electrical traces, the backside patch 506 would have to be oriented so that the direction difference between the electric field radiator 504 and the backside patch 506 is 90 degrees.

FIG6 illustrates another example of a dual-sided, 402 MHz, self-contained, circularly polarized CPL antenna 600. Antenna 600 includes a magnetic loop 602, an electric field radiator 604, a backside patch 606 serving as a second parasitic radiator orthogonal to electric field radiator 604, a transition 608, a counterpoise 610, and a balun 612. FIG6 illustrates an example of antenna 600 that uses only delay stubs to adjust the delay between electric field radiator 604 and backside patch 606. Backside patch 606 is located on the backside of antenna 600. Backside patch 606 spans the entire length of the left side of magnetic loop 602. As with backside patch 506 in FIG5 , backside patch 606 does not have a cutout portion because it is narrow.

Antenna 600 uses three delay stubs to adjust the delay between the E-field radiator 604 and the backside patch 606. FIG6 includes a large delay stub 614 positioned to the right of the balun 612, an intermediate delay stub 616 positioned along the right side of the magnetic ring 602 and before the E-field radiator 604, and a small delay stub 618 also positioned along the right side of the magnetic ring 602 but after the E-field radiator 604.

As noted above, a self-contained, circularly polarized CPL antenna can use only delay loops, only delay stubs, or a combination of delay loops and delay stubs to adjust the delay between two electric field radiators, or the delay between an electric field radiator and another element serving as a secondary electric field radiator. The antenna can use one or more delay loops of various sizes. Furthermore, some of the delay loops can have their corners cut off at an angle to improve current flow along the corners of the delay loops. Similarly, the antenna can use one or more delay stubs of various sizes. The delay stubs can also be shaped or cut accordingly to reduce capacitive coupling with other elements in the antenna. Finally, both the delay loops and delay stubs can be physically located inside the magnetic ring so that they protrude into the ring. Alternatively, the delay loops and delay stubs can be physically located outside the magnetic ring so that they protrude outside the ring. A single antenna can also combine one or more delay loops/stubs protruding into the magnetic ring with one or more delay loops/stubs protruding outside the ring. The delay ring may have a variety of shapes ranging from substantially rectangular to substantially smoothly curved shapes.

FIG7 shows another example of a dual-sided, 402 MHz, self-contained, circularly polarized CPL antenna 700. Antenna 700 includes a magnetic loop 702, an E-field radiator 704 having a small trace 706 located in the middle of the E-field radiator 704, a backside patch 708 serving as a parasitic E-field radiator orthogonal to the E-field radiator 704, a transition 710, a counterpoise 712, and a balun 714. Small trace 706 is positioned orthogonal to the E-field radiator 704 and serves to electrically extend the E-field radiator 704 for impedance tuning purposes. Thus, instead of making the E-field radiator 704 longer and having to cut away a portion of the backside patch 708 to prevent capacitive coupling between the two elements, the small trace 706, orthogonal to the E-field radiator 704, extends the E-field radiator 704 without physically extending the E-field radiator.

Antenna 700 is an example of an antenna using delay loops having a substantially smooth curved shape. Delay loop 716 is substantially arcuate. However, it should be noted that using rectangular delay loops improves antenna performance compared to using the arcuate loops shown in FIG. 7 .

Antenna 700 also includes a substantially rectangular delay stub 718. Both delay loop 716 and delay stub 718 are used to adjust the delay between horizontal E-field radiator 704 and vertical backside patch 708, which serves as a second E-field radiator.

In each embodiment of the antenna shown above, the magnetic loop as a whole has a first inductive reactance, and the first inductive reactance must be matched with the combined capacitive reactance of the other components of the antenna (e.g., the first capacitive reactance of the first electric field radiator, the second capacitive reactance of the physical arrangement between the first electric field radiator and the magnetic loop, the third capacitive reactance of the second electric field radiator, and the fourth capacitive reactance of the physical arrangement between the second electric field radiator and the magnetic loop). It should also be understood that for proper performance, other elements may contribute inductive and capacitive reactances that must be matched or balanced throughout the antenna.

FIG8A illustrates an embodiment of a double-sided (multi-layer) multi-band CPL antenna with a parasitic radiator. Antenna 800 has a length of approximately 5.08 cm and a height of approximately 2.54 cm. Antenna 800 includes a magnetic loop trace 802 on the top plane and a parasitic electric field radiator 804 (parasitic radiator) on the bottom plane. The magnetic loop of trace 802 is full wavelength, however, alternative embodiments of trace 802 may have different wavelengths. As described more fully below, trace 802 also operates as an electric field radiator at two more different frequencies. As with the other CPL antennas described above, each of the electric fields is orthogonal to each of the magnetic fields of magnetic loop 802.

Electric field radiator 804 is called a parasitic radiator because it is not physically connected to magnetic ring 802 and is resonant relative to the component it is energizing. A resonant element is one that absorbs energy and radiates energy 180 degrees out of phase with the absorbed energy. As long as the element is continuously excited by energy, the energy in the element accumulates to twice the absorbed energy. In order to radiate twice the energy the element is absorbing, the total energy must not exceed the total excited energy by more than 3dB.

Parasitic radiator 804 emits an electric field. It is important for this embodiment of the antenna to have the electric field generated by the magnetic loop 802, due to the presence of the parasitic radiator 804, located at a position along the magnetic loop parallel to the parasitic radiator 804. In addition, the electric field generated by the magnetic loop trace 802 also needs to be in phase with the electric field emitted by the parasitic radiator 804.

Even though a straight electric field radiator 804 results in the highest efficiency and gain, the parasitic radiator 804 also includes a bend or zigzag 806. Whenever a bend (such as bend 806) is introduced, it results in some cancellation of the electric field emitted by the electric field radiator. In the embodiment shown in FIG8 , a straight electric field radiator without a bend will result in capacitive coupling between the feed point or driving point 801 of the magnetic ring and the electric field radiator. Since the magnetic ring 802 is an inductor in parallel with a capacitor, this capacitive coupling will in turn cause the magnetic ring 802 to become a resonant circuit. It is desirable to make the parasitic radiator 804 the resonant element rather than the magnetic ring 802 so that the parasitic radiator 804 can be used to set the desired frequency.

The parasitic radiator 804 depicted in FIG8 is positioned inside the magnetic ring 802. In an alternative embodiment, the parasitic radiator 804 can be positioned so that more than half of the parasitic radiator 804 is inside the magnetic ring 802. Moving the parasitic radiator 804 closer to the center of the magnetic ring 802 along the back plane or bottom layer reduces the electrical length of the parasitic radiator 804. Conversely, moving the parasitic radiator 804 closer to the edge of the magnetic ring 802 increases the electrical length of the parasitic radiator 804.

The magnetic loop 802 trace is bent into one or more horizontal segments and one or more vertical segments. The magnetic loop trace 802 shown in FIG8 is symmetrical, wherein the right half of the trace is identical to the left half of the trace. However, trace 802 is only one specific embodiment of a variety of ways in which the magnetic loop trace 802 can be arranged and bent to form various horizontal and vertical segments that radiate electric fields at different frequencies. In alternative embodiments, the antenna can use an asymmetrical magnetic loop trace, wherein the right half of the trace is bent into a pattern different from the pattern of the left half of the trace.

For ease of understanding, magnetic loop trace 802 will be further described with reference to the right half of the magnetic loop trace, starting from driving point 801. Magnetic loop trace 802 includes a first horizontal segment 808 that radiates a first electric field. First horizontal segment 808 bends at a substantially 90-degree angle toward a first vertical segment 810 that reinforces first horizontal segment 808. First vertical segment 810 bends at a substantially 90-degree angle toward a second horizontal segment 814 that radiates a second electric field. Second horizontal segment 814 bends at a substantially 90-degree angle toward a second vertical segment 816 that capacitively cancels a corresponding second vertical segment on the left half of magnetic loop 802. Second vertical segment 816 bends at a substantially 90-degree angle toward a third horizontal segment 818 that radiates a third electric field. Finally, top trace 820 of magnetic loop trace 802 radiates in phase with first horizontal segment 808, and both top trace 820 and first horizontal segment 808 are reinforced by parasitic radiator 804.

The various horizontal segments of the magnetic loop traces that radiate the electric field can be moved back and forth as needed to make the electric fields more or less additive. Antenna 800 also includes a capacitive patch 812 on the back of antenna 800 that adds capacitance to first vertical segment 810. Specifically, capacitive patch 812 enables one or more electric fields generated by antenna 800 to be more in phase with each other and, therefore, add rather than subtract. Thus, capacitive patch 812 is an example of a way to tune an antenna, and specifically, an example of a way to tune the electric field generated by the antenna.

It should be understood that the capacitive patch 812 is not necessary for the antenna 800 to be properly tuned. Although one embodiment may use the capacitive patch 812 to tune the performance of the antenna, the benefits of adding the capacitive patch 812 may also be achieved by adjusting the magnetic loop trace. The magnetic loop trace may be adjusted by increasing or decreasing the size of the top trace 820; increasing or decreasing the overall width of the magnetic loop trace, making one or more sections of the magnetic loop trace 802 wider or narrower than the entire magnetic loop trace 802; adjusting the position of the bend in the magnetic loop trace 802, etc. Similarly, embodiments of the antenna 800 may use two or more capacitive patches positioned at different locations relative to sections of the magnetic loop trace 802 to tune the antenna performance.

The first horizontal segment 808 of the magnetic loop trace 802 is a quarter wavelength, although in alternative embodiments, the first horizontal segment 808 can have a different length that is a multiple of the wavelength. The first vertical segment 810 of the magnetic loop trace 802 is used for reinforcement and acts as a capacitor at the end of the quarter-wavelength monopole. As noted above, the capacitive tuning patch 812 adjusts the capacitance of the first vertical segment 810 of the magnetic loop trace 802, thereby shortening the wavelength set by the first horizontal segment 808. In addition to radiating the second frequency band, the second horizontal segment 814 of the magnetic loop 802 also offsets the capacitance added by the first vertical segment 810.

In antenna 800, capacitive patch 812 does not function as an electric field radiator because it is orthogonal to the electric field generated by the horizontal section of magnetic loop trace 802. Parasitic radiator 804 is aligned along the same plane as the horizontal section of magnetic loop trace 802 and therefore functions as a parasitic element rather than a capacitive patch. The energy radiated by parasitic radiator 804 is parallel to the electric field generated by the horizontal section of magnetic loop trace 802.

The length of parasitic radiator 804 is set based on the resonant frequency desired to be radiated by parasitic radiator 804. It should also be understood that frequency is logarithmic. Therefore, when the frequency is doubled, there is a 6dB loss in path attenuation and performance. In order for antenna 800 to operate efficiently, the length of parasitic radiator 804 is set to the lowest frequency to be generated by antenna 800, adding 3dB to the efficiency of antenna 800 at the lowest frequency. In an alternative embodiment, based on tuning for desired antenna performance, the length of parasitic radiator 804 can be set to a specific frequency among the multiple frequencies generated by antenna 800.

Antenna 800 operates at 700 MHz, 1200 MHz, and 1700 MHz to 2100 MHz. The first horizontal segment 808 of magnetic loop trace 802 (which is a YAGI element), combined with its top trace 820 and reinforced by parasitic radiator 804, generates the 700 MHz frequency band. The third horizontal segment 818 generates the 1200 MHz frequency band. The second horizontal segment 814 generates the 1700 MHz to 2100 MHz frequency band. Due to the load capacitor 812 on the back of antenna 800, the second horizontal segment 814 is capable of generating a frequency range between 1700 MHz and 2100 MHz. The entire outer rectangular outline of magnetic loop 802 is the magnetic component for the 700 MHz frequency band. As can be understood from antenna radiator 800, the segments generating the various frequency bands do not need to be in a specific order within magnetic loop 802.

As noted above, in antenna 800, certain portions of magnetic loop trace 802 are offset so that the total length of magnetic loop trace 802 is a full wavelength. The shape of magnetic loop trace 802 enables the antenna to generate a variety of frequencies, but to create the various bends that result in the horizontal and vertical segments of magnetic loop trace 802, a magnetic loop having a length greater than one wavelength is used. For example, the second vertical segments 816 cancel each other out. This allows magnetic loop trace 802 to behave as if its electrical length is one wavelength, even if the physical length of magnetic loop trace 802 is longer or shorter than one wavelength.

The curvature of magnetic loop trace 802, along with the use of cancellation and reinforcement at various points along magnetic loop trace 802, enables a single magnetic loop trace 802 to function as multiple magnetic loops of various sizes. As shown in FIG8B , a first magnetic loop 830 is formed by a first horizontal segment 808, a first vertical segment 810, and a second horizontal segment 814. A second magnetic loop is formed by the entire magnetic loop trace 802. Finally, a third magnetic loop 832 and a fourth magnetic loop 834 are formed by a second horizontal segment 814, a second vertical segment 816, and a third horizontal segment 818. However, the third and fourth magnetic loops 832 and 834 do not generate any gain or efficiency because the spacing and arrangement of these loops cause them to cancel each other. It should be further understood that magnetic loop trace 802 is curved in such a way that the various nodes with high voltages and the various nodes with high currents flowing through the magnetic loops add together at the specific frequencies desired to create a multi-band antenna.

Alternative embodiments include CPL antennas that can generate multiple frequency bands without parasitic radiators. This is achieved by positioning at least one electric field radiator within a magnetic loop to generate a first frequency band, and having various portions of the magnetic loop radiate at various frequencies, either in combination with the electric field radiator or independently, to generate additional frequency bands. FIG9A illustrates an embodiment of a 2.4/5.8 GHz multi-band CPL antenna 900. Antenna 900 is an example of an antenna having a width of approximately 1 cm and a length of approximately 1.7 cm. Antenna 900 includes a magnetic loop 902 and an electric field radiator 904 positioned within magnetic loop 902. Electric field radiator 904 is used to generate the first frequency band (2.4 GHz) of antenna 900. Electric field radiator 904 is coupled to magnetic loop 902 via a zigzag trace 906. Trace 906 couples to electric field radiator 904 at a 90-degree phase point, but it may alternatively be coupled at a 180-degree or 270-degree phase point, or at a point along magnetic ring 902 where the current flowing through magnetic ring 902 is minimally reflected. Depending on the antenna design or the desired size of the antenna, electric field radiator 904 may also be coupled directly to magnetic ring 902. For example, in antenna 900, since the electric field radiator is coupled to the top of magnetic ring 902, it is difficult to couple electric field radiator 904 directly to magnetic ring 902; thus, the need for trace 906 arises, while a different design may allow the electric field radiator to be coupled to one side of magnetic ring 902.

In antenna 900, a portion of the magnetic loop is bent in a substantially trapezoidal manner at bend 910 to produce monopole 914. Specifically, portion 916 of the magnetic loop after bend 910 is capacitively loaded to bring monopole 914 into resonance. Monopole 914 generates the higher frequency band (5.8 GHz) of antenna 900.

The electric field radiator 904 is substantially rectangular. The bottom right corner 908 of the electric field radiator 904 is cut at a certain angle to reduce the capacitive coupling between the bottom right corner 908 of the electric field radiator 904 and the bend 910 (particularly the corner 912 of the bend 910 closest to the electric field radiator 904). Depending on the desired antenna performance and other antenna requirements, cutting the corners of the electric field radiator 904 is optional and can be used in various embodiments. In an alternative embodiment, one or more corners of the electric field radiator 904 can be cut at a certain angle to reduce capacitive coupling with one or more portions of the magnetic ring (including the portion of the magnetic ring where the bend 910 or the monopole 914 is not present).

Cutting the corners of electric field radiator 904 at an angle changes the pattern and resonant frequency of electric field radiator 904. In the embodiment shown in FIG9A , it is desirable to maximize efficiency at higher frequency bands. Therefore, even though cutting the corners of the electric field radiator at an angle affects its performance, it is preferable to capacitively couple the corners of the electric field radiator to the bends of the higher frequency band.

The electrical trace 906 can be shaped in other ways, such as being straight rather than curved. As shown in FIG. 9A , the electrical trace 906 can also be shaped to have a soft and graceful curve, or to minimize the number of bends in the electrical trace 906. Furthermore, the electrical trace 906 can be modified by increasing or decreasing its thickness so that its inductance matches the total capacitive reactance of the various elements and portions of the antenna with the total inductive reactance generated by the various elements and portions of the antenna. The electrical trace 906 also increases the electrical length of the electric field radiator 204.

FIG9B shows a return loss graph for antenna 900. The return loss graph shows a first dip 920 associated with the lower frequency band and a second dip 922 associated with the higher frequency band of the antenna. The return loss graph shows the energy transmitted by antenna 900 that does not return from the antenna to the transmitter. Thus, at the two frequency bands of the antenna (2.4 GHz and 5.8 GHz), there are two corresponding return loss dips 920 and 922.

Additionally, the two dips in return loss can be moved independently of each other. Thus, the two frequency bands can be adjusted independently because they resonate independently. Embodiments of multi-band antennas can generate frequencies that are non-resonantly related without parasitic effects hindering antenna performance. It should also be understood that antenna 900 has a single feed point but is capable of generating two or more frequency bands that are non-harmonically related.

As noted, the frequency bands can be adjusted independently. For example, the electric field radiator 904 can be adjusted by changing the width or height of the electric field radiator 904, and these changes will not affect the frequency band associated with the bend 910. The monopole 914 from the bend 910 can be adjusted in frequency by adjusting the right angle of the adjacent monopole left or right. Shifting the right angle of the adjacent monopole to the right will result in a longer monopole, resulting in a lower frequency being emitted by the monopole 914. Additionally, shifting the right angle of the adjacent monopole to the left will result in a shorter monopole, resulting in a higher frequency being emitted by the monopole 914. As previously noted, having a shorter monopole will result in a smaller wavelength with a higher frequency. Conversely, having a longer monopole will result in a longer wavelength with a lower frequency.

Monopole 914 and electric field radiator 904 in bend 910 are monopoles because the dipole half is missing (the opposite is shown in FIG10 ). If the other half were a counterpoise for the monopole, it would be a dipole. In antenna 900, monopole 914 in bend 910 depends on the counterpoise, where the counterpoise is the opposite side of the magnetic loop.

FIG10 illustrates another embodiment of a 2.4/5.8 GHz antenna 1000 that uses a dipole to generate the antenna's 5.8 GHz band. Antenna 1000 includes a magnetic loop 1002 and an electric field radiator 1004 coupled to magnetic loop 1002 via a meandering trace 1006. Electric field radiator 1004 is substantially rectangular, but does not have a bottom right corner or any other corners cut off at an angle. This is intended to illustrate that antenna embodiments may or may not include an electric field radiator with a corner cut off at an angle to reduce capacitive coupling with another element of the antenna.

Generally, if the antenna elements are arranged in a specific pattern, the antenna can be tuned by cutting off the corners of one or more elements to reduce capacitive coupling between closely spaced elements. However, the total surface area of the electric field radiator affects its efficiency. Therefore, cutting off the corners of the electric field radiator reduces the antenna's efficiency. Secondly, the right angle affects the size of the magnetic loop, and the point at which reflected current is minimized also shifts as a result.

Antenna 1000 includes a first bend 1008 and a portion bent to have a second trapezoidal bend 1010, wherein first trapezoidal bend 1008 is substantially symmetrical to second bend 1010. A first quarter wavelength dimension 1012 and a second quarter wavelength dimension 1014 together form a dipole. The use of a dipole on a monopole is based on the desired radiation angle and the required impedance bandwidth.

FIG11A illustrates an embodiment of a primary Long Term Evolution (LTE) antenna 1100. LTE antenna 1100 covers a first frequency range of 698 MHz to 798 MHz, a second frequency range of 824 MHz to 894 MHz, a third frequency range of 880 MHz to 960 MHz, a fourth frequency range of 1710 MHz to 1880 MHz, a fifth frequency range of 1850 MHz to 1990 MHz, and a sixth frequency range of 1920 MHz to 2170 MHz. Antenna 1100 has a length of approximately 7.44 centimeters and a height of approximately 1 centimeter. Antenna 1100 includes a top planar surface shown in FIG11A and a back planar surface shown in FIG11B.

Antenna 1100 includes a single feed point 1102. A magnetic loop 1104 is bent to form a monopole 1106, which serves as an electric field radiator. Monopole 1106 is a radiator for frequencies up to 1800 MHz. However, other elements of antenna 1100 that radiate an electric field parallel to the electric field generated by monopole 1106 increase the gain and efficiency of the electric field radiated by monopole 1106. Thus, the electric field with the highest amplitude is radiated by monopole 1106, while other elements of antenna 1100 radiate electric fields with lower amplitudes than monopole 1106.

Central radiator 1110 is a monopole that emits an electric field with the maximum amplitude at the 915 MHz frequency band. Central radiator 1110 is coupled to magnetic ring 1104 at the 90/270 degree position via meandering trace 1112. Alternatively, central radiator 1110 can be coupled to magnetic ring 1104 at the point of minimum reflected current. At the 915 MHz frequency band, an element of the antenna (e.g., the lower left portion of the magnetic ring) can be coupled to the ground plane and thereby radiate a parallel electric field, which increases the gain and efficiency of the electric field with the highest amplitude.

The antenna's broadband characteristics enable center radiator 1110 to radiate the 850 MHz frequency band. L-shaped portion 1114 (indicated by a dashed line) of magnetic ring 1104 enables broadband characteristics that contribute to the 850 MHz frequency band. L-shaped portion 1114 comprises the right side of the right wing of magnetic ring 1104, combined with lower center radiator 1116. Specifically, when L-shaped portion 1114 of magnetic ring 1104 is capacitively coupled to center radiator 1110, the 850 MHz frequency band is radiated. Therefore, L-shaped portion 1114 increases the capacitance of center radiator 1110.

Other parts of antenna 1100 also help maximize antenna 1100's efficiency for various frequency bands. For example, the lower left side 1118 of magnetic loop 1104 also radiates in the 1800 MHz band. Furthermore, the upper left corner of the curved portion that forms monopole 1106 and the right portion of lower center radiator 1116 also radiate in the 1800 MHz band. The upper left corner of center radiator 1110 and lower left side 1118 of magnetic loop 1104 also radiate in the 1800 MHz band, thereby improving gain efficiency at this specific frequency. When one or more elements of an antenna radiate in parallel and in phase, their respective gains increase, thereby improving the antenna's overall radiation efficiency. It should be understood that embodiments are not limited to elements radiating in the specific manner described herein. As noted above, variations in antenna design may result in different antenna elements radiating at various intensities. For example, reducing the width of center radiator 1110 may result in the center radiator not radiating in the 1800 MHz band, or alternatively, radiating at a lower intensity.

The lower left side 1118 of the magnetic ring 1104 and the first monopole 1106 are the primary radiating elements in the 1900 MHz band. As noted above, the arrangement of antenna 1100 enables the various elements of antenna 1100 to radiate in various frequency bands, thereby improving the overall radiation efficiency in each frequency band. In this particular embodiment, the upper left corner of the center radiator, the right side of the lower radiator, and the area between the center radiator and the top of the magnetic ring also radiate in the 1900 MHz band.

At lower frequencies, the antenna can operate in an unbalanced mode, utilizing the applied ground plane for radiation and improving efficiency and gain. Monopole 1106 is the primary radiating element in the 1800 MHz band. In the 2100 MHz band, the primary radiating elements are the lower left side 1118 of the magnetic ring 1104, the lower half of the first monopole 1106, the right side of the lower electric field radiator 1116, the left side of the center radiator 1110, and the space between the center radiator 1110 and the top of the magnetic ring 1104. In the 750 MHz band, the primary radiating elements are the lower electric field radiator 1116 and the lower half of the center radiator. The lowermost electric field radiator 1116 radiates at a higher intensity than the lower half of the center radiator 1110. In the 850 MHz band, the primary radiating elements are the lower electric field radiator 1116 and the center radiator 1110. In the 915 MHz frequency band, the main radiating elements are the lower electric field radiator 1116 and the central radiator 1110 .

FIG11B shows the second layer of antenna 1100. Antenna 1100 includes load capacitor 1150. Load capacitor 1150 increases capacitance to account for the narrow traces of the magnetic loop on the lower left portion 1114 of magnetic loop 1104. The size of load capacitor 1150 can be increased or decreased as needed to tune the overall capacitance of antenna 1100.

It should be understood that embodiments of the multi-band antenna can be implemented on a semi-rigid or non-rigid substrate material (such as a flexible circuit board), where the left portion of the left side of the magnetic ring and the right portion of the right side of the magnetic ring are wrapped around a plastic component or some other component.

Embodiments are directed to a single-sided multi-band antenna comprising: a magnetic loop located on a plane and configured to generate a magnetic field, the magnetic loop comprising at least a first segment and a second segment, wherein the magnetic loop has a first inductive reactance that adds to a total inductive reactance of the multi-band antenna; a monopole formed by a substantially trapezoidal bend of the magnetic loop, the monopole configured to emit a first electric field in a first frequency band orthogonal to the magnetic field; and an electric field radiator located on the plane and within the magnetic loop, the electric field radiator coupled to the magnetic loop and configured to emit a second electric field in a second frequency band orthogonal to the magnetic field, wherein the electric field radiator has a first capacitive reactance that adds to a total capacitive reactance of the multi-band antenna, wherein a physical arrangement between the electric field radiator and the magnetic loop results in a second capacitive reactance that adds to the total capacitive reactance, and wherein the total inductive reactance substantially matches the total capacitive reactance.

Yet another embodiment is directed to a multi-layer planar multi-band antenna comprising: a magnetic loop located on a first plane and configured to generate a magnetic field, the magnetic loop comprising a first segment and a second segment, wherein the magnetic loop has a first inductive reactance that adds to a total inductive reactance of the multi-band antenna; a monopole formed by a substantially trapezoidal portion of the magnetic loop, the monopole configured to emit a first electric field at a first frequency band, orthogonal to the magnetic field, and wherein one or more other portions of the magnetic loop resonate in-phase with the monopole in the first frequency band; and an electric field radiator located on the first plane and within the magnetic loop, the first electric field radiator coupled to the magnetic loop and configured to emit a second electric field at a second frequency band, the emitted second electric field being orthogonal to the magnetic field, wherein the electric field radiator has a first capacitive reactance that adds to a total capacitive reactance of the multi-band antenna, wherein a physical arrangement between the electric field radiator and the magnetic loop results in a second capacitive reactance that adds to the total capacitive reactance, wherein one or more second segments of the magnetic loop resonate in-phase with the electric field radiator in the second frequency band, and wherein the total inductive reactance is substantially matched to the total capacitive reactance.

Yet another embodiment is directed to a multi-layer planar multi-band antenna, comprising: a magnetic ring located on a first plane and configured to generate a magnetic field, the magnetic ring forming two or more horizontal segments and two or more vertical segments, the two or more horizontal segments forming a substantially 90-degree angle with the two or more vertical segments, a first horizontal segment of the two or more horizontal segments emitting a first electric field in a low frequency band, and a second horizontal segment of the two or more horizontal segments emitting a second electric field in a high frequency band, wherein the magnetic ring has a first inductive reactance that adds to the total inductive reactance of the multi-band antenna; and a magnetic ring located below the first plane. A parasitic electric field radiator on a second plane, at least half of the parasitic electric field radiator being positioned on the second plane at a position that would place the electric field radiator within the magnetic ring if the position were on the first plane, the parasitic electric field radiator not being coupled to the magnetic ring, the parasitic electric field radiator being configured to emit a third electric field in a low frequency band and orthogonal to the magnetic field, the third electric field reinforcing the first electric field, wherein the parasitic electric field radiator has a first capacitive reactance that adds to a total capacitive reactance of the multi-band antenna, wherein a physical arrangement between the electric field radiator and the magnetic ring results in a second capacitive reactance that adds to the total capacitive reactance, and wherein the total inductive reactance is substantially matched to the total capacitive reactance.

In the embodiments of the antenna described herein, the total inductive reactance is matched to the total capacitive reactance, where each element of the antenna contributes to the total inductive reactance of the antenna, while other elements contribute to the total capacitive reactance of the antenna. For example, the antenna's magnetic loop has an inductive reactance that adds to the total inductive reactance, the antenna's electric field radiator has a capacitive reactance that adds to the total capacitive reactance of the antenna, and so on. When the inductive reactance of the magnetic loop matches the capacitive reactance of the electric field radiator, it means that the electric field radiator and the magnetic loop generate at the same resonant frequency and reinforce each other.

The embodiments described herein also use a discontinuous loop structure to achieve greater magnetic energy and enable the electric field radiator to increase the overall efficiency of the antenna at the desired resonant frequency. In a specific embodiment, when the antenna has two or more electric field radiators, at least one electric field radiator operates at the same frequency as the main magnetic loop. This is called the composite mode of the antenna. In the case of a multi-band antenna (with and without parasitic radiators), when the various parts of the magnetic loop operate at different frequencies, there is also at least one electric field radiator operating at the same frequency as the main magnetic loop.

FIG12 illustrates an embodiment of a 2.4/5.8 GHz single-sided, multi-band CPL antenna 1200. Antenna 1200 includes a substantially rectangular magnetic loop 1202 and an electric field radiator 1204. Magnetic loop 1202 is discontinuous, as indicated by a gap 1203 between the two endpoints of magnetic loop 1202. A trace 1206 couples electric field radiator 1204 to magnetic loop 1202. The inductive capacitance of trace 1206 can be tuned by increasing its length or width, or by changing its physical shape from a rectangular to a curved shape. While the trace can have a desired shape (having a gently curved shape), this minimizes the number of bends in trace 1206, thereby maximizing antenna performance. Electric field radiator 1204 can also be coupled directly to magnetic loop 1202 without trace 1206.

Electric field radiator 1204 resonates in the 2.4 GHz frequency band. A substantially curved trace 1208 extends downward from the left side of radiator 1204 and serves as a method for increasing the electrical length of electric field radiator 1204 and tuning its operation. Specifically, varying the shape of trace 1208 shifts the resonant frequency lower or higher, depending on the desired operating frequency. Trace 1208 can be tuned by increasing or decreasing its length, increasing or decreasing its width, or varying its shape. The electrical length of electric field radiator 1204 can also be tuned by increasing or decreasing its length, increasing or decreasing its width, or varying its shape. In one embodiment, substantially curved trace 1208 extends from the side of radiator 1204 opposite the side of radiator 1204 coupled to magnetic ring 1202. In antenna 1200, because the right side of radiator 1204 is coupled to magnetic ring 1202, trace 1208 extends from the left side of radiator 1204. If the left side of radiator 1204 were coupled to the left side of magnetic ring 1202, trace 1208 would extend from the right side of radiator 1204. If radiator 1204 were coupled to the top side of magnetic ring 1202, trace 1208 would extend from the bottom side of radiator 1204, where the bottom side of radiator 1204 is the side facing gap 1203. In the embodiments described herein, curved traces are used to minimize field cancellation.

The first arm of the magnetic loop (loop portion 1210), represented by the dashed line in FIG12 , is configured to generate a resonant mode in the 5.8 GHz frequency band. The lower right portion 1210 of the magnetic loop 1202 includes a substantially rectangular brick-shaped portion 1212 extending downward from the magnetic loop 1202. The brick-shaped portion 1212 serves as a method for tuning the capacitance and inductance of the first arm of the magnetic loop. The first arm of the magnetic loop can be tuned by varying the width and length of the brick-shaped portion 1212, varying the shape of the brick-shaped portion 1212, or varying the position of the brick-shaped portion 1212 along the first arm of the magnetic loop 1202.

FIG13 illustrates an alternative embodiment of a 2.4/5.8 GHz single-sided, multi-band CPL antenna 1300. Antenna 1300 includes a substantially rectangular magnetic loop 1302 and an electric field radiator 1304. As evident from the gap 1303 between the two endpoints of magnetic loop 1302, magnetic loop 1302 is also discontinuous. Trace 1206 couples electric field radiator 1304 to magnetic loop 1302. As described above, the inductive capacitance of trace 1306 can be tuned by varying its length, width, and shape.

Electric field radiator 1304 resonates in the 2.4 GHz frequency band. Electric field radiator 1304 includes a trace 1308 extending downward from the left side of radiator 1304. Trace 1308 is substantially curved, with the portion of trace 1308 adjacent to radiator 1304 having a greater width than the distal end of trace 1308. Trace 1308 serves as a method for tuning the electrical length of electric field radiator 1304 to shift the resonant frequency higher or lower. Trace 1308 can be tuned by varying the length, width, and shape of the portion adjacent to radiator 1304. Trace 1308 can also be tuned by varying the length, width, and shape of the distal end of trace 1308. Trace 1308 also includes various sections, wherein a first section has a greater width than a second section, and wherein a third section has a different width than the distal end of trace 1308. Trace 1308 can also taper linearly from the portion adjacent to radiator 1304 to the distal end of trace 1308. In general, the actual shape of trace 1308 may be different from the shapes shown in Figures 12 and 13. The specific shape of trace 1308 may be used as a method for impedance matching.

The first arm 1310 of the magnetic loop 1302 is configured to generate a resonant mode in the 5.8 GHz frequency band. The lower right portion 1310 of the magnetic loop 1302 includes an upwardly extending brick-shaped portion 1312 as a method for tuning the frequency and bandwidth of the antenna 1300. The antenna 1300 can be tuned by varying the length, width, and shape of the brick-shaped portion 1312. The antenna 1300 can also be tuned by varying the position of the brick-shaped portion 1312 along the first arm 1310 of the magnetic loop, or by varying how the brick-shaped portion 1312 extends from the magnetic loop (upward or downward). The brick-shaped portion 1312 is used for impedance matching. In the embodiments described herein, one or more brick-shaped portions positioned along various portions of the magnetic loop can be used as a method for tuning impedance matching. It should be understood that embodiments without brick-shaped portions, or with or without other impedance matching components, are within the scope and spirit of the present invention. For example, the geometry of one or more components of the antenna can also be varied to achieve the same impedance matching as achieved using brick-shaped portions or other shaped components. Likewise, the width of one or more sections of the magnetic loop may be varied to tune the impedance.

Although the present disclosure shows and describes a preferred embodiment and several alternative embodiments, it should be understood that the technology described herein can have many other uses and applications. Therefore, the present invention should not be limited to the specific description and various drawings contained in the specification which merely illustrate various embodiments and the application of the principles of such embodiments.

According to the embodiments of the present disclosure, the following technical solutions are also disclosed:

1. A single-sided multi-band antenna, comprising:

a magnetic ring located on a plane and configured to generate a magnetic field, the magnetic ring comprising at least a first segment and a second segment;

a monopole, the monopole being composed of a substantially trapezoidal bent portion of the magnetic ring, the monopole being configured to generate a resonant mode in a first frequency band; and

An electric field radiator is located on the plane and within the magnetic ring, the electric field radiator being coupled to the magnetic ring and configured to emit an electric field in a second frequency band orthogonal to the magnetic field.

2. The antenna according to claim 1 further includes a second monopole positioned substantially opposite to the monopole, the second monopole being formed by a second substantially trapezoidal bend of the magnetic ring, wherein the monopole and the second monopole form a dipole, and wherein the second monopole is a counterpoise of the monopole.

3. The antenna according to 1 further includes a second electric field radiator located on the plane and within the magnetic ring, the second electric field radiator being coupled to the magnetic ring and configured to emit a third electric field in a third frequency band that is orthogonal to the magnetic field.

4. The antenna according to 1, wherein the electric field radiator is substantially rectangular in shape, and wherein corners of the electric field radiator are cut at an angle to reduce capacitive coupling between the electric field radiator and the magnetic loop.

5. The antenna according to claim 1, wherein the first frequency band and the second frequency band are not harmonically related.

6. The antenna according to claim 1, wherein a portion of the magnetic loop adjacent to the monopole is capacitively loaded to cause the monopole to resonate.

7. The antenna according to claim 1 further includes an electrical trace coupling the electric field radiator to the magnetic loop.

8. The antenna of claim 7, wherein the electrical trace couples the electric field radiator to the magnetic loop at an electrical position approximately 90 degrees or approximately 270 degrees from a driving point of the magnetic loop.

9. The antenna according to claim 7, wherein the electrical trace couples the electric field radiator to the magnetic loop at a reflection minimum point where the current flowing through the magnetic loop is at a minimum reflection.

10. The antenna of claim 7, wherein the electrical trace is configured to electrically extend the electric field radiator.

11. The antenna of claim 1 , wherein the electric field radiator is directly coupled to the magnetic loop at an electrical position approximately 90 degrees or approximately 270 degrees from a driving point of the magnetic loop.

12. The antenna according to claim 1, wherein the electric field radiator is directly coupled to the magnetic loop at a reflection minimum point where the current flowing through the magnetic loop is at a minimum reflection.

13. A single-sided multi-band antenna, comprising:

a magnetic ring located on a plane and configured to generate a magnetic field, a segment of the magnetic ring comprising a substantially rectangular brick-shaped portion, the segment being configured to generate a resonant mode in a first frequency band;

an electric field radiator located on the plane and within the magnetic ring, the electric field radiator being coupled to the magnetic ring and configured to emit an electric field in a second frequency band and orthogonal to the magnetic field; and

A substantially curvilinear trace is coupled to and extends from the electric field radiator, the trace being configured to electrically extend the electric field radiator.

14. The antenna according to claim 13, wherein the brick-shaped portion is positioned within the magnetic ring.

15. The antenna according to claim 13, wherein the brick-shaped portion is positioned outside the magnetic ring.

16. The antenna according to claim 13, wherein the first frequency band and the second frequency band are not resonantly related.

17. The antenna according to claim 13, further comprising an electrical trace coupling the electric field radiator to the magnetic loop.

18. The antenna of claim 17, wherein the electrical trace couples the electric field radiator to the magnetic loop at an electrical position approximately 90 degrees or approximately 270 degrees from a driving point of the magnetic loop.

19. The antenna according to claim 17, wherein the electrical trace couples the electric field radiator to the magnetic loop at a reflection minimum point where the current flowing through the magnetic loop is at a minimum reflection.

20. The antenna of claim 13, wherein the electric field radiator is directly coupled to the magnetic loop at an electrical degree position of about 90 degrees or about 270 degrees from a driving point of the magnetic loop.

21. The antenna according to claim 13, wherein the electric field radiator is directly coupled to the magnetic loop at a reflection minimum point where the current flowing through the magnetic loop is at a minimum reflection.

22. The antenna according to claim 13, wherein the trace comprises a first segment adjacent to the electric field radiator and a second segment away from the electric field radiator, wherein the length and width of the first segment are different from the length and width of the second segment.

23. The antenna according to claim 13, wherein the trace includes a first section adjacent to the electric field radiator and a second section away from the electric field radiator, wherein a shape of the first section is different from a shape of the second section.

Claims (10)

1. A multi-layer planar multi-band antenna, comprising: A magnetic ring with a trace, the magnetic ring being located on a first plane and configured to generate a magnetic field, the trace having a first half-trace and a second half-trace, the first half-trace forming two or more horizontal segments and two or more vertical segments forming a substantially 90-degree angle between the two or more horizontal segments and the two or more vertical segments, the first horizontal segment of the two or more horizontal segments emitting a first electric field in a low-frequency band, the second horizontal segment of the two or more horizontal segments emitting a second electric field in a high-frequency band, the second half-trace including at least a first vertical segment and a second vertical segment, wherein one of the two or more vertical segments of the first half-trace capacitively cancels out the second vertical segment of the second half-trace, wherein the magnetic ring has a first inductive reactance that increases the total inductive reactance of the multi-band antenna; and A parasitic electric field radiator is located on a second plane below the first plane, wherein the parasitic electric field radiator is positioned on the second plane such that at least half of the parasitic electric field radiator is positioned inside a region on the second plane having an outer periphery aligned with the magnetic ring, the parasitic electric field radiator is not coupled to the magnetic ring, the parasitic electric field radiator is configured to emit the low-frequency third electric field, the third electric field reinforcing the first electric field and orthogonal to the magnetic field, wherein the parasitic electric field radiator has a first capacitive reactance that increases to the total capacitive reactance of the multi-band antenna, wherein the physical arrangement between the parasitic electric field radiator and the magnetic ring results in a second capacitive reactance that increases to the total capacitive reactance, and wherein the total inductive reactance is substantially matched to the total capacitive reactance. 2. The antenna according to claim 1, wherein the parasitic electric field radiator rearranges the first electric field and the second electric field to be parallel to the third electric field. 3. The antenna of claim 1, wherein positioning the parasitic electric field radiator along the second plane near the edge of the magnetic ring increases the electrical length of the parasitic electric field radiator. 4. The antenna of claim 1, wherein positioning the parasitic electric field radiator along the second plane near the center of the magnetic ring reduces the electrical length of the electric field radiator. 5. The antenna according to claim 1, wherein one or more first corners of the two or more horizontal segments and one or more second corners of the two or more vertical segments are cut at a certain angle. 6. The antenna of claim 1, wherein the two or more horizontal segments of the first half of the trace are arranged such that the electric fields radiated by the two or more horizontal segments are added together. 7. The antenna of claim 1, wherein one of the two or more vertical segments of the first half-trace and the second vertical segment of the second half-trace reduce the electrical length of the magnetic ring. 8. The antenna of claim 1, further comprising: a load capacitor located on the second plane, the load capacitor having a third capacitive reactance increased to the total capacitive reactance. 9. The antenna of claim 8, wherein the load capacitor is oriented orthogonal to the first electric field and the second electric field. 10. The antenna according to claim 1, wherein the low-frequency band and the high-frequency band are non-harmonic related.