HK1027910A - An antenna and a feed network for an antenna - Google Patents

Description

Antenna and feed network for an antenna

Background

I. Field of the invention

The invention relates to an antenna and a feed network for an antenna. More particularly, the invention relates to a helical antenna with a feed network, wherein a portion of the feed network is provided in an area coincident with a radiator of the antenna.

Description of the related Art

Contemporary personal communication devices are increasingly being used in mobile and portable applications. In conventional mobile applications, the desire to minimize the size of communication devices, such as mobile phones, has resulted in a moderate reduction in size. However, as the popularity of portable, handheld applications has increased, the demand for smaller and smaller devices has increased dramatically. Recent developments in processor technology, battery technology and communication technology have led to a significant reduction in the size and weight of portable devices over the past few years.

One area of reduced size is the antenna of the device. The size and weight of the antenna play an important role in reducing the size of the communication device. The overall size of the antenna can have a significant impact on the body of the communication device. Smaller diameter, shorter length antennas enable the overall size and body of the device to be reduced.

The size of the device is not the only factor to consider when designing an antenna for use in a mobile application. Another factor to be considered in designing an antenna is the attenuation and/or obstruction effect caused by the proximity of the user's head to the antenna during normal operation. Yet another factor is communication characteristics like radiation pattern, operating frequency, etc.

One antenna widely used in satellite communication systems is a helical antenna. The popularity of helical antennas in satellite communication systems is that they can generate and receive circularly polarized radiation for use in such systems. In addition, helical antennas are particularly useful for applications in mobile satellite communication systems and satellite navigation systems because they produce a radiation pattern that is close to hemispherical.

A conventional helical antenna is made by twisting an antenna radiator into a helical structure. A common helical antenna is a quadrifilar helical antenna which uses four radiators equally spaced around a core and excited in phase quadrature (i.e., the radiators are excited by signals that are one period or 90 degrees out of phase with respect to the quadrifilar). The typical length of the radiator is an integral multiple of one wavelength of four wires of the operating frequency of the communication device. The radiation pattern is typically determined by varying the pitch of the radiator, the length of the radiator,/, an integral multiple of one wavelength of four lines) and the diameter of the core.

Conventional helical antennas may be made using wire or ribbon technology. With the strip technology, the antenna radiator is etched or deposited on a thin, flexible substrate. The radiators are placed parallel to each other but at an obtuse angle to the edge of the substrate. The substrate is then rolled into a cylinder, cone or other suitable shape that enables the strip radiator to form a helical antenna.

Moreover, such conventional helical antennas also have the characteristic that the radiator length is an integer multiple of one wavelength of a quadrifilar of the desired resonant frequency, which results in an overall length of the antenna that is longer than is desired for some portable or mobile applications.

In addition, dual band antennas are used when transmitting and receiving information at different frequencies. However, the shape of the dual-band antenna that can be used is often not satisfactory. For example, one method of manufacturing a dual-band antenna is to stack two single-band quadrifilar helix antennas end-to-end to form a single cylinder. However, this approach has the disadvantage that the length of such an antenna is longer than desired for portable or handheld applications.

Another technique to provide dual band performance is to use two separate single band antennas. However, for handheld devices, the two antennas must be placed in close proximity to each other. However, placing two single band antennas in close proximity on a portable or handheld device can cause coupling between the two antennas, degrading performance and causing interference.

Summary of The Invention

One aspect of the present invention provides a helical antenna comprising a substrate; a radiator portion formed of a plurality of radiators on the substrate, and the plurality of radiators are formed in a spiral shape on the substrate; a feed portion adjacent to the radiator portion and including a substrate; a feed network comprising a first set of one or more traces disposed on said substrate of said feed section and a second set of one or more traces disposed on said substrate of said radiator section.

In another aspect, the present invention further provides a feed network, including: a first set of one or more traces disposed at the antenna feed portion; and a second set of one or more traces disposed on the same antenna radiator portion.

In another aspect, the present invention provides a dual-band helical antenna, comprising: a first antenna section comprising a first feed network disposed on a first surface of a first feed network section substrate of the first antenna, a first ground plane disposed on a second surface of said substrate opposite said feed network, and a first set of one or more radiators disposed on said substrate and extending from said feed network; a second antenna section including a second feed network disposed on said substrate of said second feed section and a second ground plane disposed on said substrate opposite said feed network section; a second group of one or more radiators disposed on said substrate and extending from said feed network; and providing a path for a current to flow from a radiator of the second antenna along an axis of the second antenna, thereby increasing energy emitted in a direction perpendicular to the axis; wherein the first feed network is comprised of a first set of one or more traces disposed on a first feed portion of the antenna and a second set of one or more traces disposed on a radiator portion of the first antenna portion, and the second feed network is comprised of a third set of one or more traces disposed on the second feed portion and a fourth set of one or more traces disposed on the radiator portion of the second antenna portion.

In another aspect, the present invention provides an antenna in which there are two sets of interleaved traces on a common substrate that is curved about a surface of the substrate such that the traces follow respective actual spiral paths, and a feed network is coincident with portions of the traces in the sets.

An embodiment of the present invention is a new and improved antenna feed network including a radiator portion and a feed portion. A portion of the feed network is disposed on the radiator portion of the antenna and the remainder of the feed network is disposed on the feed portion. Since the feed network portion is placed on the radiating portion, the rest of the feed network occupies less space on the feed portion. The result is that the feed portion of the antenna can be smaller than antennas with conventional feed networks. Due to the reduced area required for the feeding portion in this configuration, the feeding network can be said to be "space saving".

In a preferred embodiment, the trace of the feed network disposed on the radiator portion is disposed opposite the ground portion on the radiator. In this manner, the ground portion of the radiator serves as the ground plane for this portion of the feed network.

The feed network may be implemented with a variety of antennas having different shaped structures, including single-band and multi-band helical antennas.

One of the advantages of the present invention is that the overall size of the antenna and the amount of loss of power when fed is reduced compared to antennas with conventional feed networks.

In one embodiment, the feed network is implemented by a dual-band helical antenna having two sets of one or more helical coiled radiators. The radiator is coiled or wound and the antenna is cylindrical, conical or other suitable shape to obtain or optimize the desired radiation pattern. According to this embodiment two sets of radiators are provided, one set for operating at a first frequency and a second set for operating at a second frequency, preferably different from the first frequency. Each radiator has a feed network associated therewith for providing signals to drive the radiators. Thus, a dual-band antenna may also be described as consisting of two single-band antennas, each having a radiator portion and a feed portion.

There may be a terminal feeding the first single band antenna. The terminal extends from a feeding portion of the first single band antenna. When the antenna is cylindrical or other suitable shape, the terminal is aligned with the axis of the antenna. More particularly, in the preferred embodiment the terminals extend radially inwardly to provide a centrally located feed structure. Thus, the terminal and the feeder do not interfere with the signal pattern of the second single band antenna.

Brief Description of Drawings

The features, objects, and advantages of the present invention will become more apparent from the detailed description of the embodiments with reference to the accompanying drawings. In the drawings, like reference numerals denote like parts. Additionally, the left-most first digit of a reference number identifies the drawing in which the reference number first appears.

Fig. 1A is a schematic diagram of a conventional wire-like quadrifilar helix antenna.

Fig. 1B is a schematic diagram of a conventional strip-quadrifilar helix antenna.

Figure 2A is a schematic plan view of an open or open-terminated quadrifilar helix antenna.

Fig. 2B is a schematic plan view of the short-circuited quadrifilar helix antenna.

Figure 3 is a schematic diagram of the current distribution on a shorted quadrifilar helix antenna radiator.

Fig. 4 is a schematic illustration of the far surface of a substrate with a ribbon spiral antenna etched.

Fig. 5 is a schematic diagram of a near-surface side of a substrate with a ribbon spiral antenna etched.

Fig. 6 is a perspective view of a substrate with a ribbon spiral antenna etched.

Fig. 7A is a schematic diagram of an open-coupled multi-segment radiator having five coupled segments in accordance with an embodiment of the present invention.

Fig. 7B is a schematic diagram of a pair of short-circuit coupled multi-segment radiators in accordance with an embodiment of the present invention.

Figure 8A is a schematic diagram of a short-circuit coupled multi-segment quadrifilar helix antenna, in accordance with an embodiment of the present invention.

Figure 8B is a schematic diagram of a cylindrically coupled multi-segment quadrifilar helix antenna in accordance with one embodiment of the present invention.

Fig. 9A is a schematic illustration of the overlap δ and spacing s of the transmit segments in accordance with an embodiment of the present invention.

Fig. 9B is a schematic diagram of current distribution on a radiator segment of a coupled multi-segment helical antenna as an example.

Fig. 10A is a schematic diagram of two point sources emitting signals 90 degrees out of phase.

Fig. 10B is a schematic diagram of a field pattern of the point source shown in fig. 10A.

Figure 10C is a schematic diagram of the pattern of the circularly polarized field of a conventional helical antenna and the pattern of the circularly polarized field of a helical antenna having a feed terminal aligned with the antenna axis.

FIG. 11 is a schematic diagram of an embodiment in which each segment is positioned equidistant from both segments.

Fig. 12 is an exemplary implementation of a coupled multi-segment antenna in accordance with embodiments of the invention.

Fig. 13 is a schematic plan view of a stacked dual-band helical antenna surface in accordance with an embodiment of the invention.

Fig. 14 is a schematic diagram of a stacked dual-band helical antenna surface according to an embodiment of the present invention where the feed point of the radiator is some distance from the feed network.

Fig. 15 is a schematic plan view of an antenna terminal for stacking dual-band helical antennas in accordance with one embodiment of the present invention.

Fig. 16 is a schematic diagram of dimensions of a stacked dual-band helical antenna according to an embodiment of the invention as an example.

Fig. 17 is a schematic diagram illustrating an example of a conventional four-phase feed network.

Fig. 18 is a schematic diagram of a feed network having feed network portions extending to antenna radiator portions in accordance with an embodiment of the present invention.

Fig. 19 is a schematic diagram of a feed network for an antenna according to an embodiment of the present invention along a signal trace that includes a feed path.

Fig. 20 is a schematic diagram of a ground plane profile of an antenna in accordance with an embodiment of the present invention.

Figure 21 is a schematic diagram of the ground plane and signal trace of a superimposed dual-band antenna in accordance with one embodiment of the present invention.

Fig. 22A is a schematic diagram of a structure for maintaining an antenna in a cylindrical or other suitable shape in accordance with one embodiment of the present invention.

Fig. 22B-22E are schematic diagrams of antennas formed in a cylindrical or other suitable shape as in the embodiment of fig. 22A, in accordance with the present invention.

Figure 23A is a schematic diagram of a form of antenna suitable for supporting a cylinder or other suitable shape in accordance with embodiments of the present invention.

Fig. 23B and 23C are schematic diagrams of a process of forming a cylinder or other suitably shaped antenna according to an embodiment of fig. 23A.

Detailed description of the preferred embodiments

I. Summary and discussion of the invention

The invention relates to a space-saving antenna feed network. A portion of the feed network is disposed in the transmit section of the antenna. This reduces the area required for the antenna feed portion.

Example Environment

In a broad sense, the present invention is applicable to any system using helical antenna technology. An example of such an environment is a communications system where users communicate with others using fixed, mobile and/or portable telephones over satellite communications lines. In this example environment, the phone must have an antenna tuned to the satellite communication line.

The present invention is described in terms of this exemplary environment. The description is for convenience only. The invention is not intended to be limited to this embodiment. Indeed, after reading the following description, it will become apparent to one skilled in the relevant art how to implement the invention in other environments.

Conventional helical antenna

Before describing embodiments of the present invention in detail, it will be useful to describe the radiator portion in a conventional helical antenna. And in particular the radiator portion of some conventional quadrifilar helix antennas, is described herein throughout. Fig. 1A and 1B are schematic diagrams of a radiator portion 100 of a conventional quadrifilar helix antenna in a wire form and a strip form, respectively. The radiator portion 100 shown in fig. 1A and 1B is of a quadrifilar helix antenna, meaning that it has four radiators 104 operating in phase quadrature. As shown in fig. 1A and 1B, the radiator 104 is rolled to produce circular polarization.

Fig. 2A and 2B are schematic plan views of radiator portions of a conventional quadrifilar helix antenna. Stated another way, fig. 2A and 2B show the radiator when the antenna cylinder is spread out on a plane. Figure 2A is a schematic diagram of a quadrifilar helix antenna with an open or open termination at the distal end. In this configuration, the resonant length l of the radiator 208 is an odd integer multiple of one wavelength of four lines at the desired resonant frequency.

Fig. 2B is a schematic diagram of a quadrifilar helix antenna with a short-circuited or electrically connected distal end. In this case, the resonant length l of the radiator 208 is an even multiple of one wavelength of four lines at the desired resonant frequency. Note that in both cases the resonance length is an approximation, since small adjustments are usually required to compensate for the undesirable short or open termination.

Fig. 3 is a schematic plan view of the radiator portion of a quadrifilar helix antenna 300, which includes a radiator 208 having a wavelength l λ/2, λ being the wavelength of the desired resonant frequency of the antenna. Curve 304 represents the relative amount of current flowing at the signal on radiator 208 at the frequency f-v/λ at resonance, v being the velocity of the signal in the medium.

An exemplary embodiment of a quadrifilar helix antenna using printed circuit board technology (a strip antenna) will be described in more detail with the aid of fig. 4-6. The strip-quadrifilar helix antenna is formed from a strip-form transmitter 104A-104D etched on a dielectric substrate 406. The substrate is a thin, flexible substance rolled into a cylinder, cone, or other suitable shape such that radiators 104A-104D are helically coiled about the central axis of the cylinder.

Fig. 4 to 6 show the components that make up one quadrifilar helix antenna 100. Figures 4 and 5 are schematic illustrations of distal surface 400 and proximal surface 500, respectively, of substrate 406. The antenna 100 includes a radiator portion 404 and a feed portion 408.

In the embodiments described and illustrated below, the antenna is formed by shaping the substrate into a cylindrical shape with the proximal surface at the outer surface of the cylinder. In other alternative embodiments, the substrate is in the shape of a cylinder with the distal surface at the outer surface of the cylinder.

In one embodiment, the insulating substrate 100 is a thin, flexible layer of PTFE material, a PTFE/glass composite, or other insulating material. In one embodiment, the substrate 406 is 0.005 inches or 0.13 millimeters thick, although other thicknesses may be selected. Copper is used for the signal traces and the ground traces. In alternative embodiments, other conductive materials may be selected in place of copper, with the most preferred being based on cost, environmental considerations, and the like.

As with the embodiment shown in fig. 5, feed network 508 is etched into feed portion 408 for providing four-wire phase signals (e.g., 0, 90, 180, and 270 degree signals) to radiators 104A-104D. Distal surface 400 feed portion 408 provides ground plane 412 for feed circuit 508. The signal trace of the feed circuit 508 is etched into the near surface of the feed portion 408.

For purposes of discussion, the radiator portion 404 has a first end 432 adjacent the feed portion 408 and a second end 434 (at the other end of the radiator portion 404). Depending on the antenna embodiment implemented, radiators 104A-104D may be etched into distal surface 400 of radiator portion 404. Radiators 104A-104D extend from first end 432 to second end 434A length that is approximately an integral multiple of one wavelength of four lines at the desired resonant frequency.

In such an embodiment, radiators 104A-104D are integral multiples of λ/2, and radiators 104A-104D are electrically connected (e.g., shorted) to each other at second end 434. This connection may be made by placing a conductor across the second end 434 and forming the loop 604 around the circumference of the antenna when the substrate is formed into a cylinder. Fig. 6 is a perspective view of an etched substrate for a ribbon spiral antenna having a shorting ring 604 at a second end 434.

United states patent 5198831 (the' 831 patent for brevity) describes a conventional quadrifilar helix antenna, braun et al. The antenna described in patent 831 is a printed circuit board antenna, the radiator of which is etched or deposited on a dielectric substrate. The substrate is made cylindrical resulting in a helical profile of the radiator.

United states patent 5255005 (the' 005 patent for short) patent allen et al describes a conventional quadrifilar helix antenna, for reference. The antenna described in patent 005 is a quadrifilar helix antenna consisting of two bifilar helices placed orthogonally and excited in phase quadrature. The disclosed antenna also has a second quadrifilar helix coaxial with and electromagnetically coupled to the first helix for providing a passband of the antenna.

Another united states patent 5349365 (the 365 patent for brevity), issued to the assignee of the present invention, discloses a quadrifilar helix antenna. The antenna described in patent 365 is a quadrifilar helix antenna designed as described in figure 1A.

IV, coupling multi-section spiral antenna

To shorten the length of the antenna radiator portion 100, one type of helical antenna employs a coupled multi-segment radiator that allows for a shorter length resonance at a given frequency than would be required for a helical antenna having an equal length resonance.

Fig. 7A and 7B are schematic plan views of coupled segment helical antennas, according to an exemplary embodiment. Fig. 7A shows an open-terminated coupled multi-segment radiator 706 according to a single-wire embodiment. The antenna terminates in an open circuit, such as may be used for single, two, four, or other X-line embodiments.

The embodiment shown in fig. 7A consists of one single radiator 706. The radiator 706 is formed by a set of radiator segments. This group is composed of two end segments 708, 710 and p intermediate segments 712, where p is 0, 1, 2, 3. (p is 3 in this example). The middle segment is arbitrarily selectable (i.e., p may equal zero). The end segments 708, 710 are physically separate, but electromagnetically coupled to each other. Intermediate segment 712 is located between end segments 708, 710 and provides electromagnetic coupling between end segments 708, 710.

In an open-terminated embodiment, the length l of segment 708_s1Is an odd integer multiple of one wavelength of four lines of the desired resonant frequency. Length l of segment 710_s2Is an integral multiple of one-half wavelength of the desired resonant frequency. Length l of each of p intermediate segments 712_spIs an integer multiple of one-half wavelength of the desired resonant frequency. In the illustrated embodiment, there are three intermediate segments 712 (i.e., p ═ 3).

Figure 7B shows the radiator 706 of the helical antenna terminated in a short 722. This short circuit implementation is not suitable for a single wire antenna, but can be used for two wire, four wire, or other X-ray. In the open circuit embodiment, the radiator 706 is formed from a set of radiator segments. The radiator segments of the group are formed by two end segments 708, 710 and p intermediate segments 712, where p is 0, 1, 2, 3. (p is 3 in this example). The middle segment is arbitrarily selectable (i.e., p may equal zero). The end segments 708, 710 are physically separate, but electromagnetically coupled to each other. Intermediate segment 712 is located between end segments 708, 710 and provides electromagnetic coupling between end segments 708, 710.

In the short-circuited embodiment, the length l of the segment 708_s1Is an odd integer multiple of one wavelength of four lines of the desired resonant frequency. Length l of segment 710_s2Is an odd integer multiple of one wavelength of four lines at the desired resonant frequency. Length l of each of p intermediate segments 712_spIs an integer multiple of one-half wavelength of the desired resonant frequency. In the illustrated embodiment, there are three intermediate segments 712 (i.e., p ═ 3).

Figures 8A and 8B show schematic diagrams of coupled multi-segment quadrifilar helix antenna radiator portions 800 according to embodiments of the present invention. Fig. 8A and 8B illustrate an exemplary embodiment of an antenna as shown in fig. 7B, where p is equal to zero (i.e., no middle segment 712) and the lengths of the segments 708, 710 are one of four lines of wavelengths.

The radiator portion 800 shown in fig. 8A is a schematic plan view of a quadrifilar helix antenna having four coupled radiators 804. Each coupled radiator 804 in a coupled antenna actually includes two radiator segments 708, 710 that are in close proximity to each other so that the electrical energy of the radiator segment 708 is coupled to the other radiator segment 710.

More particularly, according to an embodiment, the radiator portion 800 can be described from having two sections 820, 824. The subsection 820 is made up of a plurality of radiator segments 708 extending from a first end 832 of the radiator portion 800 to a second end 834 of the radiator portion 800. The subsection 824 is formed from a second plurality of radiator segments 710 extending from the second end 834 of the radiator portion 800 to the first end 832 of the radiator portion 800. Towards the central region of the radiator portion 800, a portion of each segment 708 is in close proximity to an adjacent segment 710 so that electrical energy is coupled from one segment to an adjacent segment in the region in close proximity thereto. Referred to herein as overlap.

In a preferred embodiment, the length of the segments 708, 710 is about l₁＝l₂λ/4. The total length of the individual radiators consisting of the two segments 708, 710 is defined as_tot. The amount by which one segment 708 overlaps another segment 710 is given as δ ═ l₁+l₂-l_tot。

If the frequency f of the resonance is v/λ, the total length ltot of the radiator is less than half the wavelength of λ/2. In other words, as a result of the coupling, a radiator made up of a pair of coupled segments 708, 710 resonates at a frequency f-v/λ even if the total length of the radiator is less than the length of λ/2. Thus, at a given frequency f, the radiator portion 800 of the one-half wavelength coupled multi-section quadrifilar helix antenna is shorter than the radiator of the conventional one-half wavelength quadrifilar helix antenna 800.

To more clearly illustrate how the size can be reduced by using the coupling structure, the radiator portion 800 shown in fig. 8 is compared with that shown in fig. 3. At a given frequency f ═ v/λ, the length l of the conventional antenna radiator portion 300 is λ/2, while the length ltot of the radiator portion 800 of the coupled-section antenna is less than λ/2.

As described above, in one embodiment, the segments 708, 710 have a length l₁＝l₂λ/4. The length of each segment may be different, e.g./₁Is not necessarily equal to l₂And also they areNor equal to lambda/4. The actual resonant frequency of each radiator depends on the length of the radiator segments 708, 710, the distance s separating the radiator segments 708, 710, and the amount by which the segments 708, 710 overlap one another.

Note that changing the length of segment 708 relative to segment 710 can be used to adjust the bandwidth of the antenna. For example, extension l₁Making it slightly larger than lambda/4 and shortened by l₂Making it slightly shorter than λ/4 increases the bandwidth of the antenna.

Figure 8B illustrates the actual spiral configuration of a coupled multi-segment quadrifilar helix antenna according to one embodiment of the present invention. It shows how each radiator is composed of two segments 708, 710 in an embodiment. The segment 708 extends helically from the radiator portion first end 832 to the radiator portion second end 834. The segment 710 extends helically from the radiator portion second end 834 to the radiator portion first end 832. Fig. 8B also shows that a portion of the segments 708, 710 overlap so that they electromagnetically couple to each other.

Fig. 9A is a schematic illustration of the spacing s and overlap δ between radiator segments 708, 710. The spacing s is selected to couple a sufficient amount of electrical energy between the radiator segments 708, 710 to allow them to operate as a single radiator with an effective wave length of about λ/2 and integral multiples thereof.

Narrowing the spacing of the radiator segments 708, 710 to less than the optimum spacing results in increased coupling between the segments 708, 710. As a result, the length of the segments 708, 710 must be increased at a given frequency f to enable them to resonate at the same frequency f. This can be illustrated by the extreme example of actually connecting the segments 708, 710 (i.e., s-0). In this extreme example, the total length of the segments 708, 710 must be equal to λ/2 to make the antenna resonant. Note that in this extreme example, the antennas are no longer truly coupled according to the specified conditions of use and the resulting configuration is identical to the conventional helical antenna shown in fig. 3.

Likewise, increasing the amount of overlap δ between the segments 708, 710 strengthens the coupling. Thus the overlap delta increases and the length of the segments 708, 710 also increases.

To better understand the most appropriate overlap and spacing of the segments 708, 710, reference is made to FIG. 9B. Fig. 9B represents the amount of current on each segment 708, 710. The current strength indicators 911, 928 show that each segment ideally resonates at λ/4 and has the strongest signal strength at the outer end and the weakest at the inner end.

In order to perfect the antenna configuration of the coupled transmitter section antenna as much as possible, the inventors have used modeling software to determine the correct section distance/₁、l₂Overlap delta, and spacing s, among other parameters. One such software package is the "antenna optimizer" (AO) software. AO is based on an instantaneous electromagnetic antenna model algorithm. AO "antenna optimizer" version 6.35, 1994 copyright, was provided by the software by the author bayer betzle, san diego, california.

It is specifically noted that there are certain advantages to using the coupling configuration as described above and shown in fig. 8A and 8B. Using both a conventional antenna and a coupled transmitter section antenna, the current is concentrated on the end of the transmitter. This has certain advantages for use with coupled radiator segment antennas in certain applications, in terms of array coefficient theory.

By way of explanation, FIG. 10A is a schematic illustration of two point sources A, B where source A radiates a signal that is equal in phase but 90 degrees behind source B signal (e)^jωtConventional assumptions). At a distance of λ/4 between sources a and B, the signals add in phase in the direction of movement from a to B and add out of phase in the direction from B to a. As a result, very little radiation is emitted in the direction from B to a. This is illustrated by the representative field pattern in fig. 10B.

Thus, the antenna is best suited for most applications when the sources a and B are oriented with the direction from a to B facing upwards, away from the ground, and the direction from B to a facing towards the ground. This is because the user may not want the antenna to direct the signal quantity towards the ground. This configuration is particularly useful in satellite communications where most of the signal content is expected to be upward, far from the ground.

The point source antenna exemplified by fig. 10A is not possible to achieve by using a conventional one-half wavelength helical antenna. Consider the antenna radiator portion shown in figure 3. The electrical current flow is approximately a point source concentrated at the end of the radiator 208. When the radiator is coiled in a helical shape, one end of the 90 degree radiator is in line with the other end of the 0 degree radiator. Thus, the two point sources of the approximation are in a line. However, these approximate point sources are spaced by λ/2 as opposed to the desired λ/4 configuration shown in FIG. 10A.

Note that the coupled radiator segment antenna of the present invention, regardless of how it is implemented, provides an embodiment in which the approximate point sources are spaced apart at a distance approaching λ/4. Thus, the coupled radiator segment antenna allows the user to take advantage of the directional performance of the antenna as shown in fig. 10A.

The radiator segments 708, 710 as shown in fig. 8 indicate that the radiator segment 708 is very close to the segment 710 concerned, whereas each pair of segments 708, 710 is relatively far from the adjacent pair of segments. In an alternative embodiment, each segment 710 is positioned equidistantly from either side of the segment 708. This embodiment is shown in fig. 11.

Referring to fig. 11, each segment is effectively equidistant from each pair of adjacent segments. For example, segment 708B is equidistant from segments 710A, 710B. I.e. s₁＝s₂. Similarly, segments 710A are equidistant from 708A, 708B.

This embodiment is counter-intuitive in that it appears that undesirable coupling may occur. In other words, a segment corresponding to one phase will couple not only to the appropriate segment in the same phase, but also to the adjacent segment that is phase shifted. For example, segment 708B, the 90 degree segment would be coupled with segment 710A (0 degree segment) and segment 710B (90 degree segment). Such coupling does not pose a problem because radiation from tip section 710 can be viewed in two different ways. One resulting from coupling with the adjacent segment on the left side and the other resulting from coupling with the adjacent segment on the right side. However, both of these ways provide radiation in the same direction. Thus, this repeated coupling is not detrimental to the operation of coupling the multiple-segment antenna.

Fig. 12 is an exemplary implementation of a coupled radiator segment antenna. Referring now to fig. 12, the antenna is comprised of a radiator portion 1202 and a feed portion 1206. The radiator portion includes segments 708, 710. Fig. 12 provides a dimension of overlap δ of the total length of the segments 708, 710 and the radiator portion 1202.

Shown as the length of the segment in a direction parallel to the axis of the cylinder,/₁sin α is segment 708, l₂sin α is segment 710, where α is the interior angle of segments 708, 710.

The segments shown in fig. 8A and 9A above overlap, as indicated by reference number δ. The amount of overlap in the direction parallel to the antenna axis is δ sin α as shown in fig. 12.

The segments 708, 710 are separated by a spacing s that can vary as described above. The distance between the ends of the segments 708, 710 and the end of the radiator portion 1202, defined as the gap, is designated by the reference number r₁And r₂. Gap r₁，r₂May, but need not be, equal. Again, as described above, the length of segment 708 may vary relative to segment 710.

The offset of a segment 710 from one end to the next is referenced by the reference number ω₀And (4) showing. The spacing between adjacent segments 710 is indicated by reference number ω_sIs shown and depends on the diameter of the helix.

Feed portion 1206 includes a suitable feed network for providing a four-wire phase signal to radiator segment 708. The feed network is a widely known and common technology and will not be described in detail here.

In the example shown in fig. 12, the segments 708 are fed at a feed point, which is located along each segment 708, and the distance from the feed network is selected to optimize impedance matching. In the embodiment of fig. 12, this distance is denoted by the reference number δ_feed。

Note that continuous line 1224 shows the boundary of the ground portion on the far surface side of the substrate. The ground portion opposite the section 708 on the distal surface face extends to the feed point. The thin portion of segment 708 is on the proximal surface. At the feed point, the thickness of the segment 708 on the near-surface face increases.

An exemplary size of the coupled radiator segment quadrifilar helix antenna suitable for operation in the L-band of about 1.6GHz is now given. Note that this is only an example and other sizes are possible for operation in the L-band. In addition, other sizes are possible for operation in other bands.

In the exemplary L-band embodiment, the total length of the radiator portion 1202 is 2.30 inches (58.4 mm). In this embodiment, the inclination angle α is 73 degrees. With this value of angle α, the length l1sin α of segment 708 is 1.73 inches (43.9mm) for this embodiment. In the embodiment shown, the length of segment 710 is equal to the length of segment 708.

In one example, segment 710 is positioned substantially equidistant from its adjacent pair of segments 708. In one implementation of the embodiment where segment 710 is equidistant from its adjacent segment 708, the spacing s 1-s 2-0.086 inches. Other spacings are possible, including, for example, a spacing of 0.070 inch l between segment 710 and adjacent segment 708₁.8mm)。

The width of the radiator segments 708, 710 in this embodiment is 0.11 inch l₂8 mm). Other widths are also possible.

This L band embodiment is characterized by a symmetrical gap L₁＝l₂0.57 inch l₁4.5 mm). Is symmetrical at slot r to both ends of radiator portion 1202 (i.e., r₁＝r₂) Where the radiators 708, 710 have an overlap of 1.16 inches (29.5mm) (1.73 inches-0.57 inches) sin α.

Segment offset ω₀Is 0.53 inches and has a segment spacing omega_sIs 0.393 inch l₁0.0 mm). The diameter of the antenna is 4 omega_s/π。

In an embodiment, this is chosen such that the distance δ from the feed point to the feed network_feedIs delta_feed1.57 inches (39.9 mm). Other feed points can be selected to optimize impedance matching.

Note that the above-described embodiment by way of example is intended for use with a polycarbonateradome having a helical antenna thickness of 0.032 inches and contacting the radiator portion. It will become apparent to one skilled in the art how a radome or other structure affects the wavelength of the desired frequency.

Note that in the just described exemplary embodiment, the total length of the L-band antenna radiator portions is shorter than a conventional half-wavelength L-band antenna. For a conventional half-wavelength L-band antenna, the length of the radiator portion is approximately 3.2 inches (i.e., λ/2(sin α), where α is the interior angle of the segments 708, 710 with respect to the horizontal), or (81.3 mm). For the exemplary embodiment described above, the overall length of radiator portion 1202 is 2.3 inches (58.42 mm). This represents a practical reduction in size over conventional antennas.

V. stacked dual-band helical antenna

Having described several single-band helical antenna embodiments, a dual-band helical antenna embodying the present invention will now be described. The present invention is directed to a dual-band helical antenna capable of resonating at two different operating frequencies. Two helical antennas are stacked end-to-end, one antenna resonating at a first frequency and the other antenna resonating at a second frequency. Each antenna has a radiator portion comprising more than one helically wound radiator. Each antenna also has a feed portion comprising a feed network and a ground plane. The two antennas are stacked such that the ground plane of one antenna is used for a short circuit loop across the distal end of the radiator of the other antenna.

Fig. 13 is a schematic plan view illustrating a distal surface 400 and a proximal surface 500 of a dual-band helical antenna according to an embodiment of the present invention. The dual-band helical antenna consists of two single-band helical antennas: a helical antenna 1304 operating at a first resonant frequency and a helical antenna 1308 operating at a second resonant frequency.

In the embodiment shown in fig. 13, the feed network 508, radiators 104A-104D, and first antenna 1304 are disposed on the proximal surface 500 of the first antenna 1304. The ground plane 412 of the second antenna 1308 feed network 508 is also placed on the near-surface face 500. The feed network 508 and radiators 104A-104D of the second antenna 1308 and ground plane 412 for the feed portion of the first antenna 1304 are placed on the distal surface 400.

As discussed previously with reference to fig. 2A and 2B, radiators 104A-104D have a resonant length l that is an even multiple of one wavelength of four lines of the desired resonant frequency, and the distal ends of radiators 104A-104D are shorted. As shown in fig. 13, this shorting is accomplished with the ground plane 412 of the first antenna 1304. This configuration eliminates the need for additional shorting rings at the ends of radiators 104A-104D.

Note that in the embodiment shown in fig. 13, first antenna 1304 is shown resonating at an odd integer multiple of one wavelength of four lines at the desired resonant frequency because the ends of radiators 104A-104D are open-circuited. In an alternative embodiment, a shorting ring (not shown) can be added to the distal ends of the radiators 104A-104D of the first antenna 1304 and the lengths of the radiators 104A-104D can be changed so that they are even multiples of one wave of four at the desired resonant frequency.

Radiators 104A-104D of the dual-band antenna described with reference to fig. 13 are shown as being fed on a first end proximate to feed network 508. It is well known that the feed points of the radiators 104A-104D of a helical antenna can be located at any point along the length of the radiators 104A-104D, such location being initially based on impedance matching considerations. Figure 14 illustrates one embodiment of a dual-band helical antenna. In this embodiment, the feed points of radiators 104A-104D are located a predetermined distance from feed network 508. In particular, in the embodiment shown in fig. 14, the feeding point a of the first antenna 1304 is located at a distance l from the feeding network 508_feed1, the feed point B of the second antenna 1308 is located at a distance l from the feed network 508_feed2, in the drawing.

This embodiment shows radiators 104A-104D as being comprised of a ground trace 1436 on a first surface of substrate 406, a feed trace 1438 on a second surface of substrate 406 opposite the ground trace, and a radiator trace 1440 on the second surface of substrate 406.

As with the embodiment shown in fig. 13, in this embodiment, the ground plane 412 of the first antenna 1304 acts as a shorting ring for the radiators 104A-104D and the second antenna 1308, which causes the transmitter of the second antenna 1308 to resonate at even multiples of one of the four lines of wavelengths of the desired resonant frequency.

To reduce the overall length of the stacked antenna, the edge coupling technique discussed above is employed. In such an embodiment the radiators 104A-104D of the first antenna 1304 and/or the second antenna 1308 shown in fig. 13 and 14 are replaced with edge-coupled radiators such as shown in fig. 12.

One strategy for providing a dual-band antenna as shown in fig. 13 and 14 is to feed the first antenna 1304. Up to this point, the first antenna 1304 is fed by one terminal extending from a lower region of the feeding portion of the first antenna 1304.

Fig. 15 is a diagram illustrating a terminal for feeding the first antenna 1304. Referring now to fig. 15, the terminal 1504 extends from the side of the feeding portion of the first antenna 1304 on the substrate 406. In the embodiment shown in fig. 15, the terminal 1504 is approximately "L" shaped. This causes it to extend horizontally a given distance from the feeding portion of the first antenna and then to be angled axially by being centered in the direction of the feeding portion of the second antenna 1308. Although 1504 is depicted as a right angle, other angles can be used, as can curves of different radii.

When the substrate 406 is rolled into a cylinder or other suitable shape to form a helical antenna, the axial element 1524 of the terminal 1504 is effectively along the axis of the dual-band helical antenna. This is an ideal situation. The axial element 1524 of the terminal 1504 coincides with the axis of the helical antenna to minimize the effect of this component on the antenna radiation pattern. As shown in fig. 15, in a preferred embodiment, the terminal 1504 extends from the feeding portion of the first antenna 1304 at a vertical position that is as far away from the first antenna 1304 as possible. This is done to minimize the effect of the terminal 1504 on the transmission pattern of the first antenna 1304. Because the second antenna 1308 is a half-wavelength coupled antenna and the ends of the radiators 104A-104D of the second antenna 1308 are shorted by the ground plane 412 of the first antenna 1304, the terminal 1504 has minimal effect on the transmission pattern of the second antenna.

The length lgp of the feeding portion 1206 of the first antenna 1304 is preferably determined by considering two factors at the appropriate operating frequency. The first is that it is desirable to minimize the amount of current flowing from the radiator of the first antenna 1304 to the second antenna 1308, and vice versa. In other words, it is desirable to achieve isolation between the two antennas. This can be done by ensuring that the length is long enough so that the current extends from one set of radiators to another at the frequency of interest.

Another strategy is to not allow current from the first antenna 1304 radiators 104A-104D to reach the terminal 1504. Current from the first antenna 1304 decays as it flows through the feed of the first antenna 1304 toward the terminal 1504. The terminal 1504 creates an asymmetric discontinuity in these currents. Therefore, it is desirable to minimize the amount of current reaching terminal 1504 to the greatest extent practical.

After reading this description it will be clear to a person skilled in the art how to implement a feed portion 1206 having a suitable length lgp depending on the material used, the frequency of interest, the desired power value of the antenna and other known factors. This decision may also require compromises in size and performance.

Note that the role of the terminal 1504 is not absent in this embodiment. Due to the close proximity of the terminal 1504 and the radiator of the second antenna 1308, current from the second antenna 1308 is coupled to the terminal 1504 and is along the axis of the antenna. This current affects the emission of the second antenna 1308 resulting in an increase in emission towards the edges of the antenna. For applications where the antenna is mounted vertically, this may cause an increase in transmission in the horizontal direction and a decrease in transmission in the vertical direction. As a result, such applications are well suited for satellite communication systems where low earth orbit satellites are used to interrupt communications to communication equipment.

This effect is illustrated in fig. 10C, where the circularly polarized transmission pattern 1010 is a representation of a typical transmission pattern of a conventional helical antenna, and the transmission pattern 1020 is a representation of the transmission pattern of the second antenna 1308. As shown in FIG. 10C, the graphic 1020 is "flat" and "wider" than the conventional graphic 1010.

To couple a signal to the first antenna 1304, the terminal 1504 includes a connector such as a crimp connector or a solder connector or other connector suitable for connecting between the signal traces on the terminal 1504 and the feeder cable. Different types of cables or wires may be used to connect the transceiver RF circuitry to the antenna at terminal 1504. Preferably low loss flexible or semi-rigid cables are used. Of course, as is well known in the antenna art, it is desirable to match the impedance of the feed input to the interface electrical feed to maximize the power delivered to the antenna. However, if the input transition is poor, the emission pattern will still be symmetric, with a corresponding amount of reflection loss dropping in gain. In addition to low insertion loss, it is also important that the connector provide a robust mechanical connection between the cable and the terminal 1504.

An example substrate profile is also given in fig. 15. After reading this description, it will be apparent to one skilled in the art how to implement an antenna with terminal end 1504 using other shaped substrates.

Fig. 16 is a schematic diagram of an embodiment of a stacked antenna with dimensions as an example, in which the first antenna 1304 is an L-band antenna and the second antenna 1308 is an S-band antenna. The S-band antenna 1308 is in this embodiment an edge-coupled antenna in which each radiator 104 is comprised of two segments. Note that this embodiment is provided as an example only. Other frequency bands may be selected for operation. Note also that either the first antenna 1304 or the second antenna 1308, or both, may utilize edge coupling techniques.

The dimensions of the L-band and S-band antennas in fig. 16 will now be described. The total radial height of the radiating aperture of the L-band antenna is 1.253 inches, while the total aperture height of the S-band antenna is 1.400 inches. The height of the feeding portion 412 of the first antenna 1304 in this embodiment is 0.400 inches. This results in a total transmit aperture of 3.093 inches. The tilt angle of the radiators 104A-104D is 65 degrees.

The above dimensions are provided as examples only. As discussed above with reference to conventional helical antennas, the overall length of the radiators 104A-104D determines the exact resonant frequency of the antenna. The resonant frequency is very important because the highest average gain and the most symmetric pattern occur at the resonant frequency. If the antenna is made longer, the resonant frequency is shifted down. Conversely, the shorter the antenna is made, the more up the resonant frequency. The percentage of frequency shift is approximately proportional to the percentage of radiator 104A-104D increase or decrease. At the operating frequency of the L band, a length of 1mm in the antenna axis direction corresponds to 1 MHz.

In the illustrated embodiment, both the first antenna 1304 and the second antenna 1308 have four excited wire-like arms, or radiators 104A-104D. Each of the radiators 104A-104D is fed 90 degrees out of phase. For each antenna 1304, 1308, 90 degree phase-difference mode excitation of the four radiators 104A-104D is achieved with a feed network. Conventional feed networks that provide 90 degree phase difference excitation may use a preferred feed network discussed in detail below.

Another important dimension is the feed point axial length. For embodiments in which feed points are located along radiators 104A-104D as shown in fig. 13, the feed point axis length dictates the distance from the feed network to the feed point. The feed point axial length dimension indicates where the microstrip is flared to continue the radiator, and in fact the feed point location of the entire radiator 104. In the example shown in fig. 16, the feed point length of the first antenna 1304 is 1.133 inches. The feed point length of the second antenna 1308 is 0.638 inches. These dimensions produce 50 ohms impedance at 1618 and 2492MHz, respectively. If the feed point location is moved a little lower, the impedance is lower. Conversely, if the feed point location is shifted higher, the impedance is higher. It is important to note that when the total length of the radiator is adjusted to tune the frequency, the feed point position should be moved a proportional amount in the axial direction of the antenna to maintain a correct impedance match.

The antenna having the dimensions shown in fig. 16 is preferably wound on a cylinder having a diameter of 0.500 inches.

VI. feed network

The helical antenna described in this document may be implemented using a single wire, quad wire, octal wire or any other wire configuration. The feed network is used to provide signals to the lines at the necessary phase angle. The feed network separates the signals and shifts the phase provided to each line. The structure of the feeding network depends on the number of wires, for example: for a quadrifilar helix antenna, the feed network provides four equal power signals with 90 degree phase differences (i.e., 0 degrees, 90 degrees, 180 degrees, and 270 degrees).

To conserve space on the line feed portion, a unique feed network wiring may be used. The traces of the feed network extend to more than one radiator 104A-104D of the antenna. For convenience the feed network is described by a network designed to provide four equal power signals with a 90 degree phase difference. After reading these descriptions, it will become clear to one skilled in the relevant art how to implement other x-ray feed networks.

Fig. 17 shows an electrical equivalent of a conventional feed network with a phase difference of 90 degrees. For a conventional feed network with a phase difference of 90 degrees, the network provides four equal power signals, each separated in phase by 90 degrees. The signal is applied to the feed network through a first signal path 1704. At a first signal point a (referred to as the secondary feed point) a signal in phase 0 degrees is applied to the first radiator 104 and at a signal point B a signal in phase 90 degrees is applied to the second radiator 104. At signal points C and D, signals of 180 degrees and 270 degrees phase are applied to the third and fourth radiators 104.

Signals a and B combine at point P2 to produce a 25 ohm impedance. Similarly, signals C and D combine at point P3 to produce a 25 ohm impedance. These signals combine at point P1 to produce an impedance of 1.25 ohms. Thus, a 25 ohm, 90 degree transformer is placed at the input to convert this impedance to 50 ohms, noting that in the network shown in fig. 17, the transformer sections are placed before P1 splits to shorten the feedlines and reduce losses. But because it is before splitting it must be twice the impedance after splitting.

The conventional feed network is modified such that the traces of the feed network are disposed on portions of the substrate defined for radiators 104A-104D. In particular, in the preferred embodiment, the traces are disposed on an area of the substrate opposite the ground traces of more than one of the radiators 104A-104B.

Figure 18 is a schematic diagram of an exemplary embodiment of a feed network in a quadrifilar helix antenna environment. In particular, in the example of fig. 18, two feed networks are shown: a first feed network 1804 for the first antenna 1304 and a second feed network 1808 for the second antenna 1308; the feed networks 1804, 1808 have points a, B, C, and D for providing 0, 90, 180, and 270 degree signals to the radiators 104A-104D. The dashed lines in fig. 18 approximately represent the outline of the ground plane of radiators 104A-104D on the surface of the substrate opposite the surface on which the feed networks 1804, 1808 are disposed. Thus, fig. 18 shows those portions of the feed networks 1804, 1808 disposed on or extending into the radiators 104A-104D.

Note that, according to some conventional wisdom, the feed network is provided in an area designated for the feed network and separate from the radiators. In contrast, the feed network described herein is arranged such that the feed network portion is disposed at the antenna radiator portion. Because of this, the antenna feed line sections are smaller in size than the feed line sections of conventional feed networks.

Fig. 19 is a schematic diagram of the feed networks 1804, 1808 of the antennas 1304, 1308 together with the signal traces that comprise the feed paths. Fig. 20 is a schematic diagram of the ground plane profile of the antennas 1304, 1308. Fig. 21 is a schematic diagram of the superposition of both ground planes and signal traces.

One advantage of these feed networks is that the area required for the feed portion of the antenna to implement the feed network is smaller than with conventional feed techniques. This is because the feed network portion, which was originally placed in the feed portion of the antenna, is now placed in the radiator portion of the antenna. The result of this is that the overall length of the antenna can be reduced.

An additional advantage of such a feed network is that transmission line losses are reduced as the secondary feed point is moved closer to the feed point of the antenna. In addition, transformers can be integrated into the wiring of the feed network for impedance matching.

Thus, an area-saving network is constructed such that the feed network portion is positioned in the radiator portion of the antenna and the remaining portion of the feed network is positioned in the feed line portion. Since the feed network portion is placed at the radiator portion, the remaining portion of the feed network requires less area at the feed line portion. As a result, the feed portion of the antenna is small compared to antennas with conventional feed networks. It is preferable to place the trace of the feed network disposed on the radiator portion opposite the ground plane of the radiator. Because of this, the ground portion of the radiator serves as a ground plane for this portion of the feed network. This area-saving feed network can be implemented with many different types of antennas of different configurations, including single-band and multi-band helical antennas. This structure enables the overall size of the antenna and the amount of loss of the feed line to be reduced compared to antennas of conventional feed networks.

Assembly of antennas

As described above, one technique for manufacturing a helical antenna is to place the radiators, feed network and ground trace on a substrate and wind the substrate into the appropriate shape. Although the antenna structure described above may be implemented using conventional techniques for winding a substrate into a suitable shape, an improved structure and technique for winding a substrate is now described.

Fig. 22A is a schematic view of an embodiment for maintaining a substrate in a proper shape (e.g., cylindrical), and particularly fig. 22A shows an example structure applied to an antenna having a power feeding network capable of saving an area. After reading this description it will become apparent to a person skilled in the art how to implement the invention in spiral antennas of other configurations.

Fig. 22B to 22F depict cross-sectional views of structures for example, which are used to hold the antenna in a cylindrical shape and other suitable shapes. Referring now to fig. 22A through 22F, this example includes a metal strip 2118 on or extending from the ground plane 412, solder 2216 opposite the metal strip 2118, and one or more vias 2210.

The metal strip 2118 may be comprised of a portion of the ground plane 412 or a metal strip added to the ground plane 412. In one embodiment, metal strip 2218 is preferably provided by widening the width of ground plane 412 by only a predetermined amount. In the embodiment of FIG. 22A, this width is labeled ω_strip。

A series of vias 2210 are provided in the metal strip region of the ground plane 412. For a fixed connection, vias 2210 are preferably added to the radiator portions of the first antenna 1304 and the second antenna 1308. The pattern selected for vias 2210 is based on known mechanical and electrical properties of the materials used. While the present invention can be implemented with one or two vias 2210 on each ground plane 412, several vias 2210 may be used in order to obtain the desired mechanical strength and electrical contact. Each ground plane 412 used may extend laterally or all around the antenna radiator when not necessary.

As can be seen in fig. 22B, the vias 2210 extend completely through the material of the ground plane 412 and the support substrate 406(100) from one surface to the other. Vias are made from metallized or metallized vias using well known popular techniques. A relatively small portion or area of the edge 2214 opposite the ground plane 412 is plated with solder 2216.

The embodiment shown in fig. 22B and 22D includes a small metal strip 2218 formed on substrate 406 adjacent to first edge 2212 opposite ground plane 412. In this embodiment, the vias extend through the substrate to the metal strip 2218. While metal 2218 is not necessary in all applications, the ability of metal 2218 to facilitate solder flow and improved mechanical bonding will be readily apparent to those skilled in the art. The particular material from which metal strip 2218 is made is selected based on known principles based on the ground plane material used, the solder selected, and the like.

When the wire support substrate is rolled into a generally cylindrical shape to form the desired helical antenna structure, edges 2212 and 2214 are brought into close proximity to one another as shown in fig. 22D. The location of the via 2210 and metal strip 2218 (if provided) overlap with the solder 2216 on the opposite ground plane edge 2214. While the strip 2218 is held in contact with the solder 2216, heating is performed using well-known soldering techniques and equipment.

As the solder 2216 is melted, it flows into the vias 2210 and onto the metal strip 2218. The heating is then reduced or stopped and the solder forms a permanent, but removable or durable joint or bond between the two outer edges or ends of the ground plane 412. In this way, the antenna support substrate 406 and the antenna elements placed thereon now mechanically maintain the desired cylindrical shape without the need for materials like insulating tape, adhesives, etc. This reduces the time, cost and labor previously required to assemble this type of helical antenna. This also automates this operation and provides more reproducible antenna sizes. In addition, one edge of the ground plane 412 is now electrically connected to the other edge, which desirably provides a conductive loop that is continuous with the ground plane. This electrical contact is accomplished without the use of complex solder or wire.

This technique can be generalized to provide support or coupling along other portions of the antenna. For example, a string of more than one tab or strip 2220 can be placed at a distance along the length of one or both sets of antenna radiators. As can be seen in fig. 22E, the tab or strip 2220 is positioned adjacent to more than one radiator 104A-D but opposite the support substrate 406 (100). These tabs or strips are positioned so that when the antenna substrate is rolled or bent to produce the desired antenna, the metal dots or strips 2220 are positioned over a portion of the radiators 104A-D on the opposite edge of the support substrate. In particular, in one embodiment, the tab or strip 220 is positioned over the ground trace 1436 of the radiators 104A-D. Metallized vias may be formed in the contact tabs 2220, which may be desirable for application or to improve thermal conductance to melt the solder.

This can be used to attach the radiator to the strip if a small amount of solder 2226 was previously applied to the mating portion on the surface of the ground trace 1436. This provides additional connection or bonding points. These connection or junction points effectively hold the structure of the antenna together in a desired form. Where electrical connection is desired, metallized vias may be formed on the contact tabs or strips that extend to the opposite side. These metal heads may or may not be used to connect with the metal strips discussed above for the ground plane. Such a structure is very useful where very long radiators or multiple stacked antenna radiators are desired, which results in a high antenna structure.

Fig. 23A-23C are an array of views of an exemplary embodiment of a mold 2310 for rolling substrate 406 into a desired shape.

The example of fig. 23 is a cylindrical former used to roll the antenna and provide continuous support and rigidity to the antenna structure. In one embodiment, the mold 2310 can provide a series of prongs or teeth 2312 that extend radially from the outer surface of the mold 2310. To interface with the model 2310 and teeth 2312, a series of "tooling" holes or "fit guide" holes or passages 2230 are provided in the substrate 406 for mating with the teeth 2312.

In fig. 22A, tooling holes 2330 are shown placed in the ground plane 412 and the metal material of the ground plane 412 acts to stiffen the holes and prevent shape damage and movement when using a relatively soft supporting substrate material, which aids in the accuracy of the adjustment of the antenna structure. However, the holes 2230 are not required to be disposed within the metal layer.

Referring again to fig. 23A-23C and beginning with the perspective view of fig. 23A, it can be seen that substrate 406 is positioned to support mold 2310 by mating engagement of teeth 2312 with apertures 2230.

As can be seen in the side views of fig. 23B and 23C, because support model 2310 is pivoted about its axis, or substrate 406 is wrapped around model 2310, apertures 2230 engage teeth 2312 that help position substrate 406 in or above a location opposite support model 2310. Eventually, the entire substrate 406 is engaged against the support pattern. In fig. 23C, the substrate 406 is shown wrapped around the support pattern until it overlaps itself such that the strips 2218, 2220 engage the solders 2216, 2226, as previously described. Of course, where the strips 2218, 2220 and solders 2216, 2226 are not used to join portions of the substrate, the substrate 406 need not overlap on the support matrix 2310. In addition, there is no need for the support matrix 2310 to elongate the total length of the antenna, radiators 104A-D or the substrate. In some applications, some or all portions of the antenna may be self-supporting, without the need for the mold 2310. This feature may be advantageous, for example, at certain frequencies to reduce the effect of the model 2310 on the transmission pattern.

In fig. 23A-23C, only substrate 406 is shown without the metal layers of the ground plane, radiators, feed lines, feed networks, etc., for clarity and ease of illustration. It will be quite clear to those skilled in the art how to size the apertures 2230 to match the size of the teeth 2312.

As shown in FIG. 23, the mold 2310 may be constructed using solid or hollow structures formed in cylinders and other desired shapes with pointed or teeth 2312 extending therefrom. In this embodiment, the model 2310 can be thought of as a deformation of a toothed drum such as may be found in many music boxes. Other configurations may be used to provide mold 2310, including a shaft/spoke configuration, a shaft/sprocket configuration, and other suitable configurations.

Note that the spacing of the cusps 2312 or spokes is desirable for the support element to be asymmetric. That is, the spacing may be greater in certain portions in order to impart a greater amount of consistent tension on the roll, and may be smaller in certain portions in order to better control the position of the substrate where the edges of the substrate overlap. The tooth spacing is preferably selected to allow the teeth 2312 to exert a certain amount of tension to hold the substrate 406 in place so that the entire assembly is a more rigid structure.

The use of the aperture 2230 and teeth 2312 provides improved manufacturing capabilities through positioning and assembly automation with precise placement or positioning of the substrate on a mold that can be mounted within a radome. This allows for more precise structural prescription and positioning of the antenna assembly and results in more precise control and compensation of the radome effects on the transmission pattern.

The above descriptions of the placement of the metal strip 2218, solder 2216 and vias 2210 are provided by way of example, and it will be apparent to those skilled in the art after reading these descriptions how these components can be placed in various locations according to the desired configuration. For example, the elements can be positioned so that the antenna can be rolled to have either right or left hand circular polarization, and the radiators 104A-D can be either inside or outside the model.

Conclusion VIII

While various embodiments of the present invention have been described, they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

The previous description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention. While the invention has been shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.

Claims (20)

1. A helical antenna, comprising:

a substrate

A radiator part consisting of a number of radiators arranged on said substrate, wherein said substrate is shaped so that the radiators are in a helical configuration,

a feed line portion adjacent to the radiator portion and composed of a substrate,

a feed network comprising a first set of one or more traces disposed on said substrate of said feed section and a second set of one or more traces disposed on said substrate of said radiator section.

2. The helical antenna of claim 1, wherein said set of one or more traces disposed on said radiator portion is disposed in an area of said radiator portion defined for said plurality of radiators.

3. The helical antenna of claim 1 or 2, wherein each of said radiators consists of a ground trace, and wherein said set of one or more traces disposed on said feed network of said radiator portions is disposed on said substrate opposite said ground trace.

4. A helical antenna according to claim 3, wherein said trace is comprised of copper.

5. A helical antenna according to any preceding claim, wherein said helical antenna is a quadrifilar, bifilar or other x-ray antenna.

6. A helical antenna according to any preceding claim, wherein said radiator comprises a strip section disposed on said substrate.

7. A helical antenna according to any preceding claim, wherein said substrate is formed into a cylinder, cone or other suitable shape.

8. The helical antenna of any preceding claim, wherein said radiator portion comprises four radiators mounted on said substrate, said feed network providing a 90 degree phase signal to said four radiators.

9. A feed network: the method comprises the following steps:

a first set of one or more traces disposed on one antenna feed portion;

a second set of one or more traces disposed on the antenna radiator portion.

10. The feed network of claim 9, wherein said second set of one or more traces disposed on said radiator portion are disposed on an area of said radiator portion defined for said plurality of radiators.

11. The feed network of claim 9 or 10, wherein each of said radiators comprises a ground trace, and wherein the group of one or more traces of said feed network disposed on said radiator portion is disposed on a surface of said substrate opposite said ground trace.

12. The feedback network of claim 11 wherein said traces are comprised of copper.

13. The feed network of any of claims 9 to 12, wherein said antenna is a quadrifilar, quadrifilar or other x-ray helical antenna.

14. The feed network of any of claims 9 to 13, wherein the antenna is comprised of a substrate and said traces are disposed on said substrate.

15. The feed network of claim 14, wherein said substrate is formed into a cylinder, cone or other suitable shape.

16. The feed network of any of claims 9 to 15, wherein said antenna is comprised of four radiators and said feed network provides signals to said four radiators that are 90 degrees out of phase.

17. A dual-band helical antenna, comprising:

a first antenna part consisting of a first feed network arranged on a first side of the substrate on a first feed line of the first antenna,

a first ground plane disposed on the second side of the substrate opposite the feed network, an

A first set of one or more radiators mounted on the substrate and extending from the feed network;

the second group of antennas consists of the following two parts:

a second antenna portion comprising a second feed network mounted on said substrate on a second feed portion and a second ground plane mounted on said substrate opposite said feed network,

a second set of one or more radiators mounted on the substrate and extending from the feed network; and

means for providing a path for current flowing from the radiator of said second antenna along the axis of the second antenna thereby increasing the energy emitted in a direction perpendicular to the axis,

wherein the first feed network is comprised of a first set of one or more traces disposed on a first feed portion of the antenna and a second set of one or more traces disposed on a radiator portion of the first antenna portion, and the second feed network is comprised of a third set of one or more traces disposed on the second feed portion and a fourth set of one or more traces disposed on a radiator portion of the second antenna portion.

18. The antenna according to claim 17, wherein said second set of one or more traces disposed on said radiator portions are disposed in areas defining said radiator portions of said plurality of radiators.

19. An antenna according to claim 17 or 18, wherein the radiators each comprise a ground trace, and wherein one or more traces of the feed network disposed on said radiator portions are disposed on a surface of said substrate opposite said ground trace.

20. An antenna in which two sets of interdigitated tracks are provided on a common substrate, the substrate being formed into a curved surface such that the tracks follow respective substantially helical paths, and a feed network is provided coincident with a portion of a set of tracks.