Abstract:
The invention provides a method of operating a patch antenna having a radiating element. The radiating patch is excited and generates a circularly polarized radiation beam solely in a single higher order mode at a desired frequency. This allows for the radiating element to have a small surface area with the radiating beam tilted away from an axis perpendicular to the radiating element. Thus, the patch antenna provides a relatively small footprint and excellent RF signal reception from SDARS satellites at low elevation angles.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation-in-part of application Ser. No. 11/739,885, filed Apr. 25, 2007, which claims the benefit of U.S. Provisional Application No. 60/868,436, filed Dec. 4, 2006. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The subject invention relates to a method of operating a patch antenna. 
         [0004]    2. Description of the Related Art 
         [0005]    Satellite Digital Audio Radio Service (SDARS) providers use satellites to broadcast RF signals, particularly circularly polarized RF signals, back to receiving antennas on Earth. The elevation angle between a satellite and an antenna is variable depending on the location of the satellite and the location of the antenna. Within the continental United States, this elevation angle may be as low as 20° from the horizon. Accordingly, specifications of the SDARS providers require a relatively high gain at elevation angles as low as 20° from the horizon. 
         [0006]    SDARS reception is primarily desired in vehicles. SDARS compliant antennas are frequently bulky, obtuse-looking devices mounted on a roof of a vehicle. SDARS compliant patch antennas typically have a square-shaped radiating element with sides about equal to ½ of the effective wavelength of the SDARS RF signal. These patch antennas typically also include a square-shaped ground plane that has a surface area larger than that of the radiating element. When the patch antenna is disposed on a window of the vehicle, the large “footprint” defined by the radiating element and ground plane often obstructs the view of the driver. Therefore, these patch antennas are not typically disposed on the windows of the vehicle. 
         [0007]    There remains an opportunity to introduce a method of operating a patch antenna that aids in the reception of a circularly polarized RF signal from a satellite at a low elevation, especially when the patch antenna is disposed on an angled pane of glass, such as the window of a vehicle. There also remains an opportunity to introduce a method of operating a patch antenna which significantly reduces the required “footprint” of the antenna&#39;s radiating element when compared to other prior art patch antennas. 
       SUMMARY OF THE INVENTION AND ADVANTAGES 
       [0008]    The invention provides a method of operating a patch antenna at a desired frequency. The patch antenna includes a radiating element formed of a conductive material. The method includes generating a circularly polarized radiation beam solely in a single higher order mode at the desired frequency by exciting the radiating element. 
         [0009]    By generating the circularly polarized radiation beam solely in a single higher order mode the maximum gain of the radiation beam is tilted away from an axis perpendicular to the radiating element. This tilting-effect is very beneficial when attempting to receive the circularly polarized RF signals from a satellite at a low elevation angle. Additionally, by generating the circularly polarized radiation beam solely in a single higher order mode, the radiation beam remains unaffected by higher order modes other than the single higher order mode. Specifically, higher order modes other than the single higher order mode may deform the tilting of the radiation beam, thereby affecting the directivity and strength of the radiation beam with respect to the axis perpendicular to the radiating element. In turn, by generating the circularly polarized radiation beam solely in a single higher order mode, a more predictable radiation pattern and degree of tilting from the axis perpendicular to the radiating element may be achieved. In addition, the radiation beam exhibits a higher gain because all the power is radiated at the single higher order mode of interest allowing the patch antenna to more effectively receive the circularly polarized RF signals from the satellite. 
         [0010]    Furthermore, by generating the circularly polarized radiation beam solely in a single higher order mode, the dimensions of the radiating element are much smaller than many prior art radiating elements. This is very desirable to automotive manufacturers and suppliers who wish to mount the radiating element on a window of a vehicle and still maintain good visibility for a driver through the glass. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
           [0012]      FIG. 1  is a perspective view a vehicle with a patch antenna supported by a pane of glass of the vehicle; 
           [0013]      FIG. 2  is a perspective view of the patch antenna showing a radiating element, a first dielectric layer, a feed network, a second dielectric layer, and a ground plane; 
           [0014]      FIG. 3  is a cross-sectional view of a preferred embodiment of the patch antenna with the radiating element disposed on the pane of glass and electromagnetic coupling of a feed line network to the radiating element; 
           [0015]      FIG. 4  is an electrical schematic block diagram of the preferred embodiment of the patch antenna showing the radiating element, a receiver, a low noise amplifier, a first phase shift circuit, and a plurality of feed lines; 
           [0016]      FIG. 5  is a chart showing a pattern of a left hand circularly polarized radiation beam resulting from operation of the preferred embodiment of the patch antenna; 
           [0017]      FIG. 6  is a cross-sectional view of the preferred embodiment of the patch antenna taken along line  6 - 6  of  FIG. 3  showing a feed line network disposed on the second dielectric layer; 
           [0018]      FIG. 7  is a cross-sectional view of an alternative embodiment of the patch antenna with the ground plane disposed between the dielectric layers and direct electrical connection of the feed line network to the radiating element; and 
           [0019]      FIG. 8  is a bottom view of the alternative embodiment of the patch antenna taken along line  8 - 8  of  FIG. 7  and showing the feed line network disposed on the second dielectric layer. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a patch antenna  20  and associated method of operation are provided. 
         [0021]    The method of operation of the patch antenna  20  is described herein with reference to a preferred structural embodiment for the patch antenna  20 . Those skilled in the art realize that the method may be practiced with other antennas of alternative embodiments that differ in design and construction from that of the preferred embodiment. Therefore, the structure of the patch antenna  20  recited herein should not be read as limiting. 
         [0022]    In the preferred embodiment, the patch antenna  20  is utilized to receive a circularly polarized radio frequency (RF) signal from a satellite. Specifically, the patch antenna  20  may be utilized to receive a left-hand circularly polarized (LHCP) RF signal like those produced by a Satellite Digital Audio Radio Service (SDARS) provider, such as XM® Satellite Radio or SIRIUS® Satellite Radio. However, those skilled in the art understand that the patch antenna  20  may also receive a right-hand circularly polarized (RHCP) RF signal. Furthermore, in addition to receiving the LCHP and/or RHCP RF signals, the patch antenna  20  may also be used to transmit the circularly polarized RF signal. The patch antenna  20  will be described hereafter mainly in terms of receiving the LHCP RF signal, but this should not be read as limiting in any way. 
         [0023]    Referring to  FIG. 1 , the patch antenna  20  is preferably integrated with a window  22  of a vehicle  24 . This window  22  may be a part of a roof (such as a glass roof), a rear window (backlite), a front window (windshield), or any other window of the vehicle  24 . Those skilled in the art realize that the patch antenna  20  as described herein may be located at other positions on the vehicle  24 , such as on a sheet metal portion like the roof of the vehicle  24  or a side minor of the vehicle  24 . The patch antenna  20  may also be implemented in other situations completely separate from the vehicle  24 , such as on a building or integrated with a radio receiver. The rear window  22  and the windshield are typically each disposed in the vehicle  24  at an angle, such that they define a surface that is not parallel to the ground (i.e., the surface of the Earth). Therefore, the patch antenna  20  disposed on these types of windows  22  are also not parallel to the ground. 
         [0024]    The window  22  preferably includes at least one pane of glass  28 . The pane of glass  28  is preferably automotive glass and more preferably soda-lime-silica glass, which is well known for use in panes of glass of vehicles  24 . The pane of glass  28  functions as a radome to the patch antenna  20 . That is, the pane of glass  28  protects the other components of the patch antenna  20 , as described in detail below, from moisture, wind, dust, etc. that are present outside the vehicle  24 . The pane of glass  28  defines a thickness between 1.5 and 5.0 mm, preferably 3.1 mm. The pane of glass  28  also has a relative permittivity between 5 and 9, preferably 7. Of course, the window  22  may include more than one pane of glass  28 . Those skilled in the art realize that automotive windows  22 , particularly windshields, include two panes of glass sandwiching a layer of polyvinyl butyral (PVB). 
         [0025]    Referring now to  FIG. 2 , the patch antenna  20  includes a radiating element  30  formed of an electrically conductive material described additionally below. The radiating element  30  is also commonly referred to by those skilled in the art as a “patch” or a “patch element”. The radiating element  30  of the preferred embodiment defines a generally rectangular shape, specifically a square shape. Each side of the radiating element  30  measures about ¼ of an effective wavelength λ of the RF signal to be received by the patch antenna  20 . RF signals transmitted by SDARS providers typically have a frequency from 2.32 GHz to 2.345 GHz. Specifically, XM Radio broadcasts at a center frequency of 2.338 GHz. Therefore, each side of the radiating element  30  measures about 24 mm. However, those skilled in the art realize alternative embodiments where the radiating element  30  defines alternative shapes and sizes based on the desired frequency and other considerations. 
         [0026]    The patch antenna  20  also includes a ground plane  32  formed of an electrically conductive material such as, but not limited to, copper. The ground plane  32  is disposed substantially parallel to and spaced from the radiating element  30 . It is preferred that the ground plane  32  also defines a generally rectangular shape, specifically a square shape. In the preferred embodiment, the ground plane  32  measures about 60 mm×60 mm. However, the ground plane  32  may be implemented with various shapes and sizes. 
         [0027]    At least one dielectric layer  34  is disposed between the radiating element  30  and the ground plane  32 . Said another way, the at least one dielectric layer  34  is sandwiched between the radiating element  30  and the ground plane  32 . The preferred embodiment of the at least one dielectric layer  34  is described in greater detail below. 
         [0028]    In the preferred embodiment, as shown in  FIG. 3 , the pane of glass  28  of the window  22  supports the radiating element  30 . The pane of glass  28  supports the radiating element  30  by the radiating element  30  being adhered, applied, or otherwise connected to the pane of glass  28 . Preferably, the radiating element  30  comprises a silver paste as the electrically conductive material disposed directly on the pane of glass  28  and hardened by a firing technique known to those skilled in the art. Alternatively, the radiating element  30  could comprise a flat piece of metal, such as copper or aluminum, adhered to the pane of glass  28  using an adhesive. 
         [0029]    Referring now to  FIG. 4 , the patch antenna  20  of the preferred embodiment also includes a plurality of feed lines  35 . Each feed line  35  is electrically connected to the radiating element  30  at a feed port  43 . Each feed port  43  is defined as an end point, or terminus, of each feed line  35 . In the preferred embodiment, the feed ports  43  are not in contact with the radiating element  30 . Instead, the electrical connection is produced by an electromagnetic coupling between the feed ports  43  and the radiating element  30 . However, in alternative embodiments, the feed ports  43  (and accordingly, the feed lines  35 ) may come into direct contact with the radiating element  30 . 
         [0030]    In the preferred embodiment, the patch antenna  20  is implemented with four feed lines  36 ,  38 ,  40 ,  42  electrically connected to the radiating element  30  at four feed ports  44 ,  46 ,  48 ,  50 . Specifically, a first feed line  36  is electrically connected to the radiating element  30  at a first feed port  44 , a second feed line  38  is electrically connected to the radiating element  30  at a second feed port  46 , a third feed line  40  is electrically connected to the radiating element  30  at a third feed port  48 , and a fourth feed line  42  is electrically connected to the radiating element  30  at a fourth feed port  50 . The feed ports  44 ,  46 ,  48 ,  50  of the preferred embodiment are disposed with relationship to one another such that the feed ports  44 ,  46 ,  48 ,  50  define a configuration, such as corners of a square shape. Of course, the square shape is merely a hypothetical construct for easily showing the physical relationship between the feed ports  44 ,  46 ,  48 ,  50 . Those skilled in the art realize that the feed ports  44 ,  46 ,  48 ,  50  of the preferred embodiment also define a circle shape with each feed port  44 ,  46 ,  48 ,  50  about equidistant along a periphery of the circle shape from adjacent feed ports  44 ,  46 ,  48 ,  50  and a diameter equal to the diagonals of the square shape. For ease in labeling, the feed ports  44 ,  46 ,  48 ,  50  are assigned sequentially counter-clockwise around the square or circle. For example, if the feed port  43  in the upper, left-hand corner of the square is the first feed port  44 , then the second feed port  46  is in the lower, left-hand corner, the third feed port  48  is in the lower, right-hand corner, and the fourth feed port  50  is in the upper, right-hand corner. The patch antenna  20  of the preferred embodiment also includes at least one phase shift circuit  51  for shifting the phase of a base signal received by or provided by the patch antenna  20 . The base signal, which is not originally phase shifted, may be referred to as being offset by zero degrees (0°). In the preferred embodiment, the base signal is provided to a low noise amplifier (LNA)  25 . The LNA  25  is typically connected to a receiver  26  which receives the base signal from the LNA  25 . Specifically, the base signal is typically low in power, i.e., even weaker than −100 dBm. The LNA  25  amplifies the base signal with minimal noise and distortion to the base signal. In turn, the base signal maintains an acceptable signal-to-noise ratio such that once the base signal is received, the base signal produces quality audio. The LNA  25  is typically placed near the patch antenna  20  in order to reduce losses, noise, and distortion introduced by and getting through the path between the LNA and the patch antenna  20 . Of course, in other embodiments in which the patch antenna  20  is used to transmit, the base signal is provided by a transmitter (not shown). 
         [0031]    In the preferred embodiment, as shown in  FIG. 4 , the at least one phase shift circuit  51  is implemented as a first phase shift circuit  52 . The first phase shift circuit  52  shifts the base signal by about ninety degrees (90°) to produce a first phase-shifted signal. Those skilled in the art realize that the 90° phase shift could vary by up to ten percent with little impact on overall performance. The first phase shift circuit  52  is electrically connected to the second feed line  38  and the fourth feed line  42 , and thus applies the first phase-shifted signal (90°) to the second feed port  46  and the fourth feed port  50 . As a result, the first phase-shifted signal (90°) is applied at opposite corners of the square. The LNA  25  is electrically connected to the first feed line  36  and the third feed line  40 . Thus, the base signal (0°) is applied to the first feed port  44  and the third feed port  48 , also at opposite corners of the square. As a result of the 90° delay between application of the base signal and application of the first phase-shifted signal, a circularly polarized radiation beam is produced. Those skilled in the art will realize alternate embodiments to produce the circularly polarized radiation beam using different configurations of phase shift circuits  51 . In addition, the first phase shift circuit  52  may produce a plurality of phase-shifted signals to apply to the feed ports  44 ,  46 ,  48 ,  50 . In other words, the first phase shift circuit  52  may continuously shift the base signal by about ninety degrees (90°) to produce a first phase-shifted signal (0°), a second phase-shifted signal (90°), a third phase-shifted signal (180°), and a fourth phase-shifted signal) (270°). It is to be appreciated that the first phase-shifted signal (0°) in this example is the base signal, and the base signal need not necessarily pass through the phase shift circuit  52 . In turn, the first phase shift circuit  52  may apply the first, second, third, and fourth phase-shifted signals to each of the feed ports  44 ,  46 ,  48 ,  50  in any suitable order or frequency. However, as described above, the base signal may be directly applied to the any one of the feed ports  44 ,  46 ,  48 ,  50  without having to pass through the first phase shift circuit  52 . Additionally, the feed line network  58  may implement any combination of different phase shifts. 
         [0032]    As stated above, the subject invention provides a method of operating the patch antenna  20 . This method includes the step of generating a circularly polarized radiation beam solely in a single higher order mode at the desired frequency by exciting the radiating element  30 . In conventional patch antennas, excitation of a higher order mode simultaneously excites additional modes, including a fundamental mode and higher order modes other than the single higher order mode. However, as will be described below, excitation of both the fundamental mode and higher order modes other than the single higher order mode is not desired for the subject invention. Specifically, the circularly polarized radiation beam excited by the patch antenna  20  of the subject invention is not generated in a fundamental mode, but only in only one higher order mode. That is, the operating mode of the patch antenna  20  consists of a single higher order mode and no higher order mode other than the single higher order mode. Preferably, the single higher order mode is a transverse magnetic mode. More preferably, the single higher order mode is a TM22 mode. However, those skilled in the art realize that the other higher order modes besides the TM22 mode may achieve acceptable results. 
         [0033]    Generating the circularly polarized radiation beam solely in a single higher order mode is accomplished due to the application of the base signal and the phase-shifted signals to the radiating element  30 , along with the configuration in which the feed ports  44 ,  46 ,  48 ,  50  are disposed with respect to one another. In the preferred embodiment, each side of the square defined by the feed ports  44 ,  46 ,  48 ,  50  measures about ⅙ of the effective wavelength of the resulting radiation beam. Said another way, each feed port  44 ,  46 ,  48 ,  50  is separated from two other adjacent feed ports  44 ,  46 ,  48 ,  50  by about ⅙ of the effective wavelength. The configuration of the feed ports, and more particularly the spacing between the feed ports  44 ,  46 ,  48 ,  50  is dependent on the desired operating frequency of the patch antenna  20 , which, in the preferred embodiment, is about 2.338 GHz. Within the teaching of the present invention, the dimensions may be modified by one skilled in the art for alternative operating frequencies. Furthermore, the effective wavelength depends on the window  22  and the dielectric layers  34 . As such, the permittivity and thickness of these elements has an effect on the size of the patch as is appreciated by those skilled in the art. 
         [0034]    By generating the circularly polarized radiation beam solely in a single higher order mode, a null is established in the radiation beam at an axis perpendicular to the radiating element  30 . Said another way, the pattern of the radiation beam shows a null in the broadside direction, as is shown in  FIG. 5 . Furthermore, a maximum gain of the radiation beam is about 40-50 degrees offset the axis perpendicular to the radiating element  30 . The maximum gain in the circularly polarized radiating beam may also be produced at an angle at an angle at least 20 degrees offset from the axis perpendicular to the radiating element, or at an angle at least 35 degrees offset from the axis perpendicular to the radiating element. Thus, the radiation beam is “tilted” (or “steered”). This tilting-effect is very beneficial when attempting to receive the circularly polarized RF signals from a satellite at a low elevation angle, e.g., an XM radio satellite. More significantly, by generating the circularly polarized radiation beam solely in a single higher order mode, the pattern of the radiation beam remains unaffected by higher order modes other than the single higher order mode. Specifically, if higher order modes other than the single higher order mode having a resonant frequency close to the desired frequency of the single higher order mode are present at the outset of generating the circularly polarized radiation beam, the higher order modes other than the single higher order mode may distort the radiation beam. In other words, the higher order modes other than the single higher order mode may deform the “tilting” of the radiation beam, thereby affecting the directivity and strength of the radiation beam with respect to the axis perpendicular to the radiating element  30 . In turn, generating the circularly polarized radiation beam solely in a single higher order mode produces a more predictable radiation pattern and degree of “tilting” from the axis perpendicular to the radiating element  30 . Additionally, the radiation beam exhibits a higher gain because all the power is radiated at the single higher order mode of interest allowing the patch antenna  20  to more effectively and predictably receive the circularly polarized RF signals from the satellite. It is to be appreciated that the aforementioned advantages and effects of generating the circularly polarized radiation beam solely in a single higher order mode may be realized for either a LHCP radiation beam or a RHCP radiation beam. 
         [0035]    Furthermore, by generating the circularly polarized radiation beam solely in a single higher order mode, the dimensions of the radiating element  30  are much smaller than many prior art radiating elements  30 . This is very desirable to automotive manufacturers and suppliers who wish to lessen the amount of obstruction on the windows  22  of the vehicle  24 . Additionally, the use of less conductive material in the radiating element  30  may also reduce manufacturing costs and enhance and improve aesthetics. 
         [0036]    The method of operating the patch antenna  20  also includes the step of shifting the phase of a base signal to produce at least one phase-shifted signal. This may be accomplished, as described above, with one or more phase shift circuits  51 . In the preferred embodiment, this step includes shifting the phase of the base signal by 90 degrees to produce a first phase-shifted signal. 
         [0037]    The method of operating the patch antenna  20  may also include the step of feeding the base signal to the radiating element  30  through at least one of the plurality of feed ports  44 ,  46 ,  48 ,  50  and feeding the at least one phase-shifted signal to the radiating element  30  through at least one of the other feed ports  44 ,  46 ,  48 ,  50 . In the first implementation, the step includes feeding the base signal through the first and third feed ports  44 ,  48  and feeding the first phase-shifted signal through the second and fourth feed ports  46 ,  50 . In the second implementation, the step includes feeding the base signal through the first feed port  44 , feeding the first phase-shifted signal through the second feed port  46 , feeding the second phase-shifted signal through the third feed port  48 , and feeding the third phase-shifted signal through the fourth feed port  50 . 
         [0038]    Referring again to  FIG. 2 , in the preferred embodiment, the at least one dielectric layer  34  is implemented as a first dielectric layer  60  and a second dielectric layer  62 . The first dielectric layer  60  is in contact with the ground plane  32 . The second dielectric layer  62  is in contact with the radiating element  30 . Preferably, the first and second dielectric layers  60 ,  62  are at least partially in contact with one another. The width of the dielectric layers  60 ,  62  is based, in part, on the dielectric constant of the dielectric layers  60 ,  62 . Preferably, the dielectric constant of both dielectric layers  60 ,  62  is about 4.5. The width of the second dielectric layer  62  is about 1/20 of the effective wavelength and the width of the first dielectric layer  60  is about 1/60 of the effective wavelength. 
         [0039]    The patch antenna  20  preferably includes a feed line network  58  formed of conductive strips  59  as shown in  FIG. 6 . The conductive strips  59  act as the feed lines  36 ,  38 ,  40 ,  42  and feed line ports  44 ,  46 ,  48 ,  50  described above. The feed line network  58  also defines an input port  64  which may be electrically connected to the receiver  26  and/or the LNA  25 . 
         [0040]    In the preferred embodiment, where the feed lines  36 ,  38 ,  40 ,  42  are electromagnetically coupled to the radiating element  30 , the feed line network  58  is sandwiched between the first and second dielectric layers  60 ,  62 . The conductive strips  59  of the feed line network  58  are disposed either on the first dielectric layer  60  or the second dielectric layer  62  at the junction of the dielectric layers  34 . The conductive strips  59  may be etched on one of the dielectric layers  34  by processes known to those skilled in the art. 
         [0041]      FIGS. 7 and 8  show an alternative embodiment where there is a direct connection between the feed lines  36 ,  38 ,  40 ,  42  of the feed line network  58  and the radiating element  30 . In this alternative embodiment, the ground plane  32  is sandwiched between the first and second dielectric layers  60 ,  62 . The feed line network  58  is disposed on the first dielectric layer  60  on the opposite side from the ground plane  32 . A plurality of pins  66  electrically connect the feed lines  36 ,  38 ,  40 ,  42  of the feed line network  58  to the radiating element  30 . Passage holes (not numbered) are defined in the ground plane  32  to allow the plurality of pins  66  to pass between the feed line network  58  and the radiating element  30  through the ground plane  32  such that the plurality of pins  66  do not become electrically shorted to the ground plane  32 . 
         [0042]    In both the preferred and alternative embodiments, the feed line network  58  is also utilized to shift the phase of a signal applied to the feed lines  36 ,  38 ,  40 ,  42 , thus, acting as the phase shift circuits  51  described above. This phase shifting is accomplished due to the inductive and capacitive properties of the conductive strips  59  of the feed line network  58 . The inductive and capacitive properties of the conductive strips  59  are determined by the impedance and length of each conductive strip  59 . The impedance of each conductive strip  59  is determined by the frequency of operation, the width of each conductive strip  59 , the dielectric constant of the first dielectric layer  60 , and the distance between the conductive strips  59  and the ground plane  32 . In the described embodiments, a conductive strip  59  width of about 1/60 of the effective wavelength yields an impedance of about 70.71 ohms and a width of about 1/35 of the effective wavelength yields an impedance of about 50 ohms. 
         [0043]    The feed line network  58  shown in  FIG. 6  implements the 0°, 90°, 0°, and 90° phase shifts. As can be seen, the conductive strips  59  form divergent paths which alternate between the various widths. Resistors  68  electrically connect between the divergent paths to ensure that an equal amount power is carried to or from each feed line port  44 ,  46 ,  48 ,  50 . Those skilled in the art realize that the feed line network  58  could be designed to perform other phase shifts or in a manner that does not perform any phase shifts. 
         [0044]    Those skilled in the art realize that many of the Figures are not drawn to scale. This is particularly evident in the cross-sectional representations of the various embodiments of the patch antenna  20  in  FIGS. 3 and 7 . Particularly, in these Figures, the width of the electrically conductive components, such as the radiating element  30 , the ground plane  32 , and the feed line network  58 , is exaggerated such that it may be seen from the cross-sectional view. Those skilled in the art also realize that the width of these electrically conductive components may be much less than 1 mm and therefore difficult to perceive from an actual cross-sectional view of the patch antenna  20 . 
         [0045]    The present invention has been described herein in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Obviously, many modifications and variations of the invention are possible in light of the above teachings. The invention may be practiced otherwise than as specifically described within the scope of the appended claims.