Patent Publication Number: US-9431713-B2

Title: Circularly-polarized patch antenna

Description:
BACKGROUND 
     The present disclosure relates to planar patch antennas, and in particular to circular patch antennas having circular polarization. 
     Patch antennas, also referred to as microstrip antennas, are often used in radio frequency (RF) systems due to their small size, light weight, low profile, low cost, and ease of fabrication and assembly. Patch antennas typically include a conductive (e.g., metallic) patch portion separated from a large metallic ground plane by a low-loss dielectric spacer, such as quartz, alumina, ceramics, or other dielectric materials. The patch portion, separated from the ground plane by the dielectric, is typically energized via a RF feed. The patch portion and ground plane together form a transmission line that radiate electromagnetic fields from the edges of the patch. The resonant frequency (and hence the wavelength) of the antenna is dependent upon factors such as the size of the patch, the size of the ground plane, and the thickness and dielectric constant of the dielectric spacer. 
     Typically, such antennas utilize a patch portion that is approximately one-half of a wavelength of the frequency of operation. For instance, a patch antenna having a nominal operational frequency within the 2.4 gigahertz (GHz) Industrial, Scientific, and Medical (ISM) radio band may typically utilize a patch portion approximately 2.5 inches (6.35 centimeters) long, corresponding to approximately one-half of the wavelength of a 2.4 GHz signal in free space. As such, the size of the patch can make it difficult to integrate patch antennas into certain assemblies (e.g., sensors, transmitters, and the like) having size requirements that are less than the half-wavelength size of a signal at a specified nominal operational frequency (e.g., less than 2.5 inches in the case of a 2.4 GHz signal). Typically, patch antenna require electrically large ground planes (e.g., five times the size of the patch or more), thereby further impeding such integration efforts. Integration of patch antennas into certain assemblies, such as assemblies having metal housings, can further complicate matters by introducing proximity effects which can change the resonant frequency, as well as the bandwidth (BW). 
     Miniaturization efforts have been undertaken to help reduce the size of patch antennas. Resulting techniques have disclosed that the use of a dielectric spacer having a higher dielectric constant can decrease the size of the patch portion of the antenna, but at the expense of a reduced bandwidth. In addition, circular polarization can be helpful in operation in harsh operations. However, inciting circular polarization within a patch may typically require the use of a quadrature coupler that equally splits a RF power feed into multiple (e.g., two) phase-shifted signals that feed the patch at multiple points (e.g., opposite edges). Such quadrature couplers can be bulky in comparison to the patch antenna, thereby impeding miniaturization and integration efforts. Accordingly, it can be difficult to integrate patch antennas into assemblies having metal housings that are smaller than the half-wavelength size of a signal at a specified nominal operational frequency of the antenna. 
     SUMMARY 
     In one example, a patch antenna includes a conductive ground plane layer, a conductive circular patch layer, a dielectric layer, a grounding connection, and a RF feed. The conductive circular patch layer includes a plurality of voids. The dielectric layer is disposed between and contacts each of the ground plane layer and the circular patch layer. The grounding connection extends from the ground plane layer through the dielectric layer and contacts the circular patch layer at a grounding location of the circular patch layer. The RF feed extends through the ground plane layer and the dielectric layer and contacts the circular patch layer at a RF feed location of the circular patch layer. The RF feed location is offset from a central axis of the circular patch layer. 
     In another example, an assembly includes an electronics module, a patch antenna, and an electrical cable. The patch antenna includes a conductive ground plane layer, a conductive circular patch layer, a dielectric layer, a grounding connection, and a RF feed. The conductive circular patch layer includes a plurality of voids. The dielectric layer is disposed between and contacts each of the ground plane layer and the circular patch layer. The grounding connection extends from the ground plane layer through the dielectric layer and contacts the circular patch layer at a grounding location of the circular patch layer. The RF feed extends through the ground plane layer and the dielectric layer and contacts the circular patch layer at a RF feed location of the circular patch layer. The RF feed location is offset from a central axis of the circular patch layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a top view of a patch antenna having a conductive ground plane layer and a conductive circular patch layer. 
         FIG. 2  is a side view of the patch antenna of  FIG. 1 . 
         FIG. 3  is a perspective view of the back side of the patch antenna of  FIG. 1  connected to an electrical feed line. 
         FIG. 4  is a perspective view of an assembly including the patch antenna of  FIG. 1  electrically connected to an electronics module. 
         FIG. 5  is a graph of a predicted input return loss of a patch antenna. 
         FIG. 6  is a graph of the predicted input return loss of  FIG. 5  and a measured input return loss of a corresponding patch antenna. 
         FIG. 7  is a schematic diagram of a wireless latch sensor including a patch antenna. 
     
    
    
     DETAILED DESCRIPTION 
     According to techniques described herein, a patch antenna includes a conductive ground plane layer separated from a conductive circular patch layer by a dielectric layer. A grounding connection extends from the ground plane, through the dielectric layer, and contacts the circular patch at a grounding location. A radio frequency (RF) feed contacts the patch at an RF feed location that is offset from a central axis of the patch. The offset RF feed location can excite multiple resonant modes of the patch, thereby inciting circular polarization of the antenna to help improve the efficiency of the antenna system. In this way, a patch antenna according to techniques of this disclosure can be circularly-polarized without the use of a quadrature coupler or other phase-shifting device which may increase the size of the antenna system. In some examples, the dielectric layer can be formed of a material having a relatively high dielectric constant (e.g., alumina), thereby reducing the diameter of the patch. For instance, in certain examples, an antenna implementing techniques of this disclosure can have a nominal operational frequency in the 2.4 gigahertz (GHz) Industrial, Scientific, and Medical (ISM) radio band, but a patch diameter of less than one inch (as opposed to a 2.5-inch diameter corresponding to the half-wavelength of a 2.4 GHz signal in air). 
     The patch can include a plurality of voids that can impede the flow of a portion of the surface currents on the patch, thereby effectively increasing the diameter of the patch and resulting in an increased bandwidth of the antenna. In some examples, the antenna can include a “finite” ground plane (i.e., a ground plane layer that is less than five times the diameter of the patch). For instance, in certain examples, the diameter of the circular patch layer can be nearly equal to the diameter of the ground player layer. Accordingly, a patch antenna implementing techniques of this disclosure can have an outer diameter that is significantly less than a half-wavelength of a signal at a nominal operational frequency (e.g., less than half of the half-wavelength) while maintaining sufficient bandwidth. Moreover, the circularly-polarized patch antenna can be mounted within a housing, such as a metal housing, without significantly reducing the performance of the antenna. 
       FIG. 1  is a schematic diagram of a top view of patch antenna  10  having ground plane layer  12  and patch layer  14 . As illustrated, patch layer  14  can include grounding location  16 , RF feed location  18 , voids  20 A and  20 B (collectively referred to herein as “voids  20 ”), and tuning portion  22 . 
     As in the example of  FIG. 1 , patch layer  14  can be a circular patch having diameter D P  and formed of metal (e.g., copper) or other highly conductive material. Likewise, ground plane layer  12  can be formed of metal (e.g., copper) or other highly conductive material. Ground plane layer  12 , as illustrated in  FIG. 1 , can be circular, having diameter D G . In other examples, ground plane layer  12  can have other shapes, such as square, rectangular, oval, or other regular or irregular shapes. Ground plane layer  12  is separated from patch layer  14  (and tuning portion  22 ) by a dielectric layer, as is further described below. 
     Patch layer  14  is electrically connected to ground plane layer  12  via a grounding connection that extends from ground plane layer  12 , through the dielectric layer, and contacts patch layer  14  at grounding location  16 , as is further described below. As illustrated in  FIG. 1 , grounding location  16  can be disposed at a central axis of patch layer  14  (i.e., an axis that extends through a center point of patch layer  14 , out of the page in the illustrated example). In other examples, grounding location  16  can be disposed at a location that is offset from the central axis of patch layer  14 . In general, grounding location  16  provides a shorting location for current to flow from RF feed location  18  to ground plane layer  12 . 
     RF feed location  18 , as illustrated in  FIG. 1 , is disposed at a location of patch layer  14  that is offset from the central axis of patch layer  14  (i.e., the axis extending through patch layer  14  at grounding location  16  in this example). For instance, axis  24 A and axis  24 B (collectively referred to herein as “axes  24 ”) can be perpendicular axes that each intersect the central axis of patch layer  14  to divide patch layer  14  into four quadrants  26 A- 26 D (collectively referred to herein as “quadrants  26 ”). As illustrated, RF feed location  18  can be disposed at a location of patch layer  14  that is distance D 1  from axis  24 A and distance D 2  from axis  24 B. Distance D 1  and distance D 2  can be the same or different distances, each ranging from zero to fifty percent of a diameter of patch layer  14 . In certain examples, distance D 1  and distance D 2  can be selected such that angle θ, measured between line  28  extending from the central axis of patch layer  14  to feed location  18  and axis  24 A extending through voids  20 , is approximately forty-five degrees, such as within a range from forty-three degrees to forty-seven degrees. 
     In some examples, RF feed location  18  can be determined based on an impedance matching of a RF feed line (e.g., a coaxial cable) that supplies a RF signal to patch layer  14  at RF feed location  18 . For instance, RF feed location  18  can be selected as a location of patch layer  14  having an impedance that most closely matches an impedance of the RF feed line (e.g., fifty ohms), thereby increasing efficiency of power transfer from the RF feed line to patch layer  14 . In the example of  FIG. 1 , an impedance of patch layer  14  at grounding location  16  is effectively zero, and an impedance at the periphery of patch layer  14  approaches infinity, or open circuit. The grounding connection that electrically connects ground plane layer  12  and patch layer  14  can facilitate such impedance matching by reducing the effect that proximity to other electrically conductive materials (e.g., a metal housing) can have on the patch layer  14 . 
     In operation, RF energy is applied to patch layer  14  via the RF feed (illustrated in  FIG. 2 ) at RF feed location  18  to excite the electro-magnetic (EM) fields between patch layer  14  and ground plane layer  12 . In response, patch antenna  10  emits and/or receives signals within a range of frequencies that are closely related to one or more exited resonant frequencies of patch layer  14 . The exited resonant frequencies are dependent upon factors such as the diameter of patch layer  14 , the thickness and dielectric constant of the dielectric layer, the guide wavelength of the signal in the dielectric layer, and the wavelength of the signal in free space. For instance, a fundamental excitation mode of patch layer  14  can correspond to a wavelength of emitted radiation that is approximately twice diameter D P  of patch layer  14 . That is, diameter D P  can be approximately half of a wavelength of a signal emitted and/or sensed by patch antenna  10  at a nominal operational frequency of patch antenna  10 , such as a nominal operational frequency of 2.45 GHz, 915 megahertz (MHz), or other nominal operational frequencies. In general, the nominal operational frequency of patch antenna  10  can be any operational frequency, and corresponding diameters, thicknesses, and other dimensions of patch antenna  10  can be adjusted accordingly to accommodate a particular nominal operational frequency. 
     Patch layer  14 , in some examples, can be approximated as a half-wave resonator for its fundamental excitation mode. As one example, properties of patch antenna  10  can be estimated via the following equation: 
                     D   p     =         2   ⁢   r     ≈       λ   8     2       =       1   2     ⁢     (       λ   o         ɛ   r         )                 (     Equation   ⁢           ⁢   1     )               
where r is the radius of the circular patch, ∈ r  is the dielectric constant of the dielectric layer, λ g  is the guide wavelength of the signal in the dielectric layer, and λ o  is the wavelength of the signal in free space. As can be seen by the relationships established in Equation 1, as the dielectric constant of the dielectric layer increases, the radius (and hence the diameter) of patch layer  14  for a given wavelength decreases. In this way, diameter D P  of patch layer  14  can be reduced while maintaining the same resonant frequency. Moreover, given a nominal operational frequency and a specified diameter of patch antenna  10  (or a maximum diameter), a dielectric material can be chosen such that the dielectric constant of the material satisfies Equation 1. For instance, given a maximum diameter of one inch (2.54 cm) and a nominal operational frequency of 2.45 GHz, an alumina substrate can be selected for use in the dielectric layer. As another example, a ceramic-polytetrafluoroethylene (PTFE) composite having a similar dielectric constant to alumina (e.g., approximately 9.9) can be selected.
 
     As another example, properties of patch antenna  10  can be approximated using a cavity model that approximates a cavity composed of two perfect electric conductors representing patch layer  14  and ground plane  12 , and a cylindrical perfect magnetic conductor around the circular periphery of the cavity. Using the cavity model, the resonant frequency of patch layer  14  (e.g., a circular patch layer) can be determined via the following equation: 
                       f   o     =       cJ   mn       2   ⁢   π   ⁢           ⁢     r   eff     ⁢       ɛ   r             ,           (     Equation   ⁢           ⁢   2     )               
where f 0  is the resonant frequency, J mn  is the m th  zero of the derivative of the Bessel function of order ‘n’, r eff  is the effective radius of patch layer  14  (modified due to the fringing fields), and ∈ r  is the dielectric constant of the dielectric layer.
 
     The effective radius r eff  of patch layer  14  can be determined according to the following equation: 
                       r   eff     =     r   ⁢       1   +         2   ⁢   h       π   ⁢           ⁢   r   ⁢           ⁢     ɛ   r         ⁡     [       ln   ⁡     (       π   ⁢           ⁢   r       2   ⁢   h       )       +   1.7726     ]               ,           (     Equation   ⁢           ⁢   3     )               
where r is the physical radius of patch layer  14 , h is the thickness of the dielectric layer, and ∈ r  is the dielectric constant of the dielectric layer. For the dominant mode TM 11 , J mn  can be approximated as 1.84118, which is an industry accepted approximation.
 
     Using Equations 2 and 3, it can be estimated, for example, that diameter D P  of patch layer  14 , having a nominal operating frequency of 2.45 GHz and using a dielectric layer having a dielectric constant of 9.9 a thickness of 0.100 inches is approximately 0.85 inches (2.16 cm). As can be seen by the above relationships, an increased dielectric constant of the dielectric layer can result in a value of diameter D P  of patch layer  14  that is significantly less than a half-wavelength of a signal at a nominal operational frequency of patch antenna  10 . For instance, rather than a diameter of approximately 2.5 inches (6.35 cm) corresponding to a half-wavelength of a 2.45 GHz signal in air, the diameter D P  of patch layer  14  can be reduced to approximately 0.85 inches (2.16 cm). 
     In operation, as RF energy is fed to patch layer  14  at RF feed location  18 , multiple resonance modes of patch layer  14  are excited, thereby inducing circular polarization of patch antenna  10 . In addition, surface currents flow from the RF feed point on patch layer  14 , eventually to ground via grounding location  16 . Moreover, a portion of the surface currents follow a path that circumvents one or more of voids  20 , thereby increasing a path length of that portion of the currents. By increasing the path length of a portion of these currents, voids  20  can act to increase an effective diameter of patch layer  14 . This is turn will increase the bandwidth of patch antenna  10 . 
     As illustrated in  FIG. 1 , voids  20  can be rectangular voids having a major axis extending along axis  24 A and a minor axis extending in a direction of axis  24 B. In other examples, voids  20  can have other shapes, such as a square shape, an elliptical shape, or other shape. In the example of  FIG. 1 , patch layer  14  includes two voids  20 A and  20 B. In other examples, patch layer  14  can include more than two voids  20 , such as three or more voids  20 . In certain examples, such as the example of  FIG. 1 , voids  20  can be disposed symmetrically about the central axis of patch layer  14 . A length of the major axis of each of voids  20 , in some examples, can range from one-fifth to one-fourth of diameter D P  of patch layer  14  (and hence, from approximately one-tenth to one-eighth of a RF signal wavelength at a nominal operational frequency of patch antenna  10 ). A length of the major axis of each of voids  20  ranging from one-fifth to one-fourth of diameter D P  can, in some examples, help to increase the bandwidth of patch antenna  10  while maintaining sufficient input impedance matching performance. 
     As illustrated in  FIG. 1 , patch antenna  10  can further include tuning portion  22  that extends along a portion of an outer periphery of patch layer  14 . In general, tuning portion  22  can extend along any portion of the periphery of patch antenna  10  to adjust the frequency response of patch layer  14 , such as to meet specified requirements of patch antenna  10 . In some examples, tuning portion  22  can extend along the periphery of one of quadrants  26  of patch layer  14 . In certain examples, as in the example of  FIG. 1 , tuning portion  22  can extend along the periphery of one of quadrants  26  that is opposite axis  24 B (i.e., an axis perpendicular to axis  24 A extending through voids  20 ) and adjacent the one of quadrants  26  in which RF feed location  18  is disposed. For instance, in the example of  FIG. 1 , electrical feed location is disposed within quadrant  26 A. Tuning portion  22 , in this example, extends along the periphery of quadrant  26 B that is adjacent quadrant  26 A and opposite axis  24 B. 
     Ground plane layer  12 , as illustrated in  FIG. 1 , can have diameter D G  that is greater than diameter D P  of patch layer  14 . Diameter D G , in certain examples, can be less than five times diameter D P  of patch layer  14 . A diameter D G  that is less than five times diameter D P  can be termed a “finite” ground plane, while a diameter D G  that is five or more times diameter D P  can be termed an “infinite” ground plane. In some examples, diameter D P  can be nearly equal to diameter D G . For instance, a ration of diameter D P  to diameter D G  can be greater than 0.95. 
     According to techniques described herein, patch antenna  10  can be fed via a single RF feed at RF feed location  18  that is offset from a central axis of patch layer  14 , thereby inducing circular polarization of radiation emitted and/or received via patch antenna  10  without the use of a hybrid coupler device to shift the phase of the input signal. Such circular polarization can facilitate the integration of patch antenna  10  into assemblies, such as a housing, that may be formed of a conductive material (e.g., metal) without sacrificing performance. Moreover, voids  20  in patch layer  14  increase an effective bandwidth of patch antenna  10 . A dielectric layer formed of a material having a high dielectric constant (e.g., alumina) and a finite ground plane enable patch antenna  10  to have a physical diameter that is significantly less than a half-wavelength of a signal at a nominal operational frequency, thereby facilitating integration of patch antenna  10  into smaller assemblies and/or sub-assemblies. 
       FIG. 2  is a side view of patch antenna  10 . As illustrated in  FIG. 2 , patch antenna  10  includes ground plane layer  12  and patch layer  14  separated by dielectric layer  30  having thickness T. Patch antenna  10  further includes grounding connection  32  and electrical feed  34 . Grounding connection  32  extends from ground plane layer  12  through dielectric layer  30  and contacts patch layer  14  at grounding location  16  to electrically connect ground plane  12  with patch layer  14 . Grounding connection  32  can be a wire, post, or other connection formed of a highly conductive material, such as metal (e.g., copper). 
     RF feed  34  extends through ground plane layer  12  and dielectric layer  30  to contact patch layer  14  at RF feed location  18 . RF feed  34  can be a wire, a coaxial cable, or other connector capable of delivering RF energy to patch layer  14 . Dielectric layer  30  is disposed between and contacts each of ground plane layer  12  and patch layer  14  (including tuning portion  22  illustrated in  FIG. 1 ). Dielectric layer  30  can be formed of any one or more dielectric materials, such as alumina, ceramic-PTFE, quartz, FR-4 and the like. 
       FIG. 3  is a perspective view of patch antenna  10  showing electrical feed  34  connected to a back side of ground plane layer  12 . As illustrated, electrical feed  34  can be a coaxial cable that connects to patch antenna  10  via an orifice through ground plane layer  12 . Electrical feed  34  can attach (e.g., via solder) to ground plane layer  12  at mounting location  36  to help relieve strain on electrical feed  34  during assembly and operation of patch antenna  10 . 
       FIG. 4  is a perspective view of assembly  38  including patch antenna  10  and electronics module  40 . In general, electronics module  40  can be any electrical module that can provide RF signal to patch antenna  10  to cause patch antenna  10  to transmit and/or receive radio frequency (RF) signals. For instance, as in the example of  FIG. 4 , electronics module  40  can be a printed circuit board. Electronics module  40  is electrically connected to patch antenna  10  via electrical feed  34 . 
       FIG. 5  is a graph of a predicted input return loss  42  of patch antenna  10  that was obtained via mathematical modeling techniques. In the example of  FIG. 5 , dielectric layer  30  has a thickness T of 2.54 millimeters (mm) and is formed of a material having a dielectric constant of approximately 10.2. In addition, patch layer  14  has diameter D P  of 20 mm, and each of slots  20  have major dimensions of 7 mm and minor dimensions of 4 mm. Tuning portion  22 , in the example of  FIG. 5 , extends along a periphery of quadrant  26 B and has a width of 0.5 mm. 
     As illustrated in  FIG. 5 , a predicted bandwidth of patch antenna  10  ranges from a frequency of 2.3526 GHz at location  44  to a frequency of 2.5713 GHz at location  46 . Input return loss  42  has a predicted maximum value of −2.275 decibels (dB) within the bandwidth region at location  48 , which determines a predicted threshold sensitivity of patch antenna  10  for operation within the bandwidth region. As described herein, each of the diameter D P  of patch layer  20 , the dielectric constant and thickness of dielectric layer  30 , the location and size of voids  20  within patch layer  12 , the position of feed location  18 , the diameter D G  of ground plane layer  12 , and the position and size of tuning portion  22  contribute to increase return loss  42  to help maximize the desired bandwidth range (e.g., 10 dB). As such, patch antenna  10  can transmit and/or receive signals at a nominal operational frequency (e.g., 2.45 GHz) utilizing a patch layer (e.g., patch layer  14 ) and finite ground plane layer (e.g., ground plane layer  12 ) having a maximum outer diameter that is significantly less than a half-wavelength of the signal at the nominal operational frequency in air. 
       FIG. 6  is a graph of predicted input return loss  42  and measured input return loss  50  corresponding to patch antenna  10  as described above with respect to  FIG. 5 . That is,  FIG. 6  shows a graph of predicted input return loss  42  and a corresponding measured input return loss  50  for patch antenna  10  where dielectric layer  30  has a thickness T of 2.54 millimeters (mm) and is formed of a material having a dielectric constant of approximately 10.2, patch layer  14  has diameter D P  of 20 mm, each of slots  20  have major dimensions of 7 mm and minor dimensions of 4 mm, and tuning portion  22  extends along a periphery of quadrant  26 B and has a width of 0.5 mm. 
     As illustrated in  FIG. 6 , predicted input loss  42  and measured input loss  50  show basic agreement with respect to bandwidth and resonant modes. Discrepancies between predicted input loss  42  and measured input los  50  can be attributed to, in part, the use of relatively long test cables (e.g., six inch test cables), as well as simplifications and approximations of the prediction model. 
       FIG. 7  is a schematic diagram of wireless latch sensor  52  including patch antenna  10 . As illustrated in  FIG. 7 , wireless latch sensor  52  can include housing  54 . Each of patch antenna  10 , electronics module  40 , and sensor  56  can be disposed within housing  54 . Housing  54  can be formed of any one or more rigid and/or semi-rigid materials, such as plastic, ceramic, metal (e.g., stainless steel, aluminum, etc.) or other such materials. Examples of sensor  56  can include pressure sensors, temperature sensors, flow sensors, or other types of sensors. As illustrated, patch antenna  10  can be disposed within housing  54  such that an outer periphery of patch antenna  10  abuts housing  54 . In other examples, patch antenna  10  can be disposed within housing  54  such that patch antenna  10  does not contact housing  54 . In operation, sensor  56  senses one or more parameters (e.g., temperature, pressure, etc.) and transmits an indication of the parameter to electronics module  40 , which can be a printed circuit board, a printed circuit board including a radio unit, an application specific integrated circuit (ASIC), a processor, a field programmable gate array (FPGA), or other type of electronics module. Electronics module  40  connects to patch antenna  10  via electrical feed  34  to cause patch antenna  10  to transmit an RF signal corresponding to the sensed parameter. 
     It should be understood, however, that wireless latch sensor  52  is just one example of an assembly into which patch antenna  10  can be integrated. There may be many more suitable applications and assemblies for which techniques of this disclosure may find applicability. 
     The following are non-exclusive descriptions of possible embodiments of the present invention. 
     A patch antenna includes a conductive ground plane layer, a conductive circular patch layer, a dielectric layer, a grounding connection, and a RF feed. The conductive circular patch layer includes a plurality of voids. The dielectric layer is disposed between and contacts each of the ground plane layer and the circular patch layer. The grounding connection extends from the ground plane layer through the dielectric layer and contacts the circular patch layer at a grounding location of the circular patch layer. The RF feed extends through the ground plane layer and the dielectric layer and contacts the circular patch layer at a RF feed location of the circular patch layer. The RF feed location is offset from a central axis of the circular patch layer. 
     The patch antenna of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components: 
     The grounding location can be disposed at the central axis of the circular patch layer. 
     The plurality of voids can be disposed symmetrically about the grounding location. 
     An angle between a first line extending from the grounding location to the RF feed location and a second line extending through the plurality of voids can be between forty-three degrees and forty-seven degrees. 
     A diameter of the circular patch layer can be equal to half of a wavelength in the dielectric layer of a signal at a nominal operational frequency of the patch antenna. A diameter of the ground plane layer can be greater than the diameter of the circular patch layer. A ratio of the diameter of the circular patch layer to the diameter of the ground plane layer can be greater than 0.95. 
     The dielectric layer can be formed of a low-loss material having a dielectric constant between 1.0 and 50.0. 
     The low-loss material can include alumina. 
     Each of the plurality of voids can be a rectangular void. 
     Each of the plurality of rectangular voids can have a length along a major axis of the respective one of the plurality of rectangular voids that ranges from one-tenth to one-eighth of a wavelength of a signal at a nominal operational frequency of the patch antenna. 
     The patch antenna can further include a tuning portion that extends along a portion of an outer periphery of the circular patch layer. 
     The plurality of voids can be disposed symmetrically about the grounding location. A first axis extending through each of the plurality of voids and a second axis extending perpendicular to the first axis can define four quadrants of the circular patch layer. The tuning portion can extend along an outer periphery of a first quadrant. The RF feed location can be disposed within a second quadrant, the second quadrant opposite the second axis and adjacent the first quadrant. 
     A nominal operational frequency of the patch antenna can be 2.45 gigahertz (GHz). 
     An assembly includes an electronics module, a patch antenna, and an electrical cable. The patch antenna includes a conductive ground plane layer, a conductive circular patch layer, a dielectric layer, a grounding connection, and a RF feed. The conductive circular patch layer includes a plurality of voids. The dielectric layer is disposed between and contacts each of the ground plane layer and the circular patch layer. The grounding connection extends from the ground plane layer through the dielectric layer and contacts the circular patch layer at a grounding location of the circular patch layer. The RF feed extends through the ground plane layer and the dielectric layer and contacts the circular patch layer at a RF feed location of the circular patch layer. The RF feed location is offset from a central axis of the circular patch layer. 
     The assembly of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components: 
     The assembly can further include a housing. Each of the electronics module, the patch antenna, and the electrical cable can be disposed within the housing. 
     The housing can be formed of metal. 
     While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.