Abstract:
A system and method improves linearly-polarized microstrip patch antenna performance and fabrication through the incorporation of a pin fin ground plane and an integral antenna feed assembly. In one embodiment, a patch antenna system includes an antenna area with a patch antenna that provides radio communications. A heat dissipation member is coupled to the antenna area and includes a plurality of pins that provide for both the dissipation of heat from the antenna area and a ground plane for the antenna area. An antenna feed line is further coupled with the antenna patch for providing an electrical connection from the antenna patch to other electronic circuitries, such as a wireless device that may be mechanically coupled to the heat dissipation member. Heat generated during the operation of the wireless device is directed to ambient air by way of the heat dissipation member.

Description:
CROSS REFERENCE 
   The present application claims the benefits of U.S. Provisional Patent Application Ser. No. 60/612,054, which was filed on Sep. 22, 2004 and entitled “CPE-Pin Fin Ground Plane for a Patch Antenna”. 

   BACKGROUND 
   The present invention relates generally to patch antennas, and more particularly to the utilization of a pin fin ground plane structure for a linearly-polarized patch antenna. 
   Patch antennas are planar antennas used in wireless links and other microwave applications. A conventional linearly-polarized, single-band patch antenna consists of a dielectric substrate with a ground plane on the back-side of the dielectric substrate. On the front-side of the dielectric substrate is a square or rectangular conductive area also known as a “patch”, which gives patch antenna its name. Typically a coaxial cable acts as a feed line to and from the “patch” for transmitting or receiving signals. In addition, the length of the patch in the direction of the feed is typically slightly less than half a wavelength of the operating frequency. 
   The ease of patch antenna fabrication on a flat substrate is a main selling point of the patch antenna. Though patch antennas have low gain as compared to large dish/parabolic type antennas, they can be arranged in an array to achieve higher gains. A commercial patch antenna, when opened up, typically involves an array of different shaped patches. For linearly-polarized radiation, the simplest patch element is a rectangle. 
   However, there are certain deficiencies with respect to a conventional patch antenna design. The resonant length of a conventional patch antenna is directly proportional to the intrinsic speed of light in the dielectric substrate over a flat ground plane, which is typically a published value for the substrate material. The radiating structure is a half wave resonating structure. An electric field exists between the patch and the ground plane. Since the field is not fully enclosed near its edges, fringing fields, which in turn is a source of radiation, are generated. Other factors also influence the resonant frequency of the patch antenna. These factors include: ground plane size, dielectric substrate thickness, metal (copper) thickness, and patch width (impedance). The width of the patch is chosen to provide a suitable radiation resistance and operational bandwidth. 
   Desirable in the art of linearly-polarized microstrip patch antenna, are improved patch antenna designs that provide for smaller size, lower weight, and decreased fabrication and assembly costs while maintaining conventional patch antenna performance. 
   SUMMARY 
   In view of the foregoing, this invention provides a structure and assembly methods to improve linearly-polarized microwave patch antenna fabrication and performance through the incorporation of a pin fin ground plane and an integral antenna feed assembly. The pin fin structure also acts as a heatsink. 
   In one embodiment, a patch antenna system comprises an antenna area with an antenna patch that provides radio communications. A heat dissipation area is coupled to the antenna area and comprises a plurality of pins and provides a ground plane for the antenna area. An antenna feed line is further coupled with the antenna patch for providing an electrical connection from the antenna patch to other electronic circuitries, such as a wireless electronic device. Unlike conventional patch antennas, the feed line and the antenna patch are fabricated as a single part. The ground plane of the antenna patch also serves as the ground plane for the feed line as well as an EMI shield. The new patch antenna design results in simplified fabrication and assembly processes, thereby lowering cost. 
   The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  presents a diagram with a conventional linearly-polarized microstrip patch antenna. 
       FIG. 2  presents a diagram with two linearly-polarized microstrip patch antennas in accordance with one embodiment of the present invention. 
       FIG. 3  presents two isometric views of the linearly-polarized microstrip patch antenna in accordance with one embodiment of the present invention. 
   

   DESCRIPTION 
   The following will provide a detailed description of an improved patch antenna design. 
     FIG. 1  presents a diagram with a conventional linearly-polarized microstrip patch antenna  102 . In other exemplary embodiments, patch antennas other than microstrip patch antennas may be used. The conventional patch antenna  102  includes a dielectric substrate  104 , a ground plane  106  on the rear of the dielectric substrate  104 , a conductive patch  108  on the front of the dielectric substrate  104 , and a RF feed line  110 , which is typically a coaxial cable. It is understood by those skilled in the art that the thickness of the dielectric substrate  104  is magnified for clarity, and thus is not indicative of proportions with respect to other elements presented in the diagram. A RF electronics module  112  connects to the conductive patch  108  via the RF feed line  110  and a probe feed  114 . For example, in the transmit mode, a RF signal is created in the RF electronics module  112 , conducted down the RF feed line  110  and the probe feed  114 , and further conducted into the conductive patch  108 . The RF energy: generates an electric field  116  between the conductive patch  108  and the ground plane  106 . Since the electric field  116  is not fully enclosed near the edges of the conventional patch antenna  102 , fringe fields  118  are created, which is the antenna radiation source. As another example, in the receive mode, a received radiated signal sets up a small electrical field within the conventional patch antenna  102 . The signal is detected by the probe feed  114  and sent to the RF electronics module  112 , via the RF feed line  110 , for further processing. 
     FIG. 2  presents a diagram with linearly-polarized microstrip patch antennas  200  and  201  in accordance with one embodiment of the present invention. The patch antennas  200  and  201  have a smaller size when compared with conventional patch antennas. Each of the patch antennas  200  and  201  has two functional areas: an antenna area  202  and a heat dissipation area or member  206 . It is understood in each patch antenna, parts of the two functional areas, which may have overlapping areas, form an integrated single-piece structure. It is further understood that the integrated single-piece structure simplifies overall fabrication and assembly. 
   A wireless electronic device  204  is positioned between the two patch antennas  200  and  201  and may be oriented vertically in an exemplary embodiment. The wireless electronic device  204  may be a wireless modem but other wireless electronic devices may be used in other embodiments. The heat dissipation area  206 , which may include a pin fin heatsink, is attached to both sides of the wireless device  204  to facilitate passive heat transfer from the device to ambient air. The heat dissipation area  206  is a structure having a plurality of pins  208  protruding from the surface of the heat dissipation area  206  to maximize the surface area for heat transfer. The heat dissipation area  206  may be formed of aluminum in an exemplary embodiment. It is understood that the pins  208  may include a cylindrical, elliptical, square or rectangular shape and may be formed of aluminum, other metals or other suitable heatsink materials. The heat dissipation area  206  also acts as an electromagnetic interference shield to prevent electromagnetic emissions to and from the wireless device  204 . 
   The antenna area  202  of each of the patch antennas  200  and  201  comprises a patch  210 , a dielectric substrate  212 , and uses its mechanical connection with the heat dissipation area  206  as its ground plane. It is understood that while the antenna area  202  is mechanically connected to the heat dissipation area  206 , it is also electrically isolated therefrom by the dielectric substrate  212 . 
   One advantage of using the heat dissipation area  206  as the ground plane of the antenna areas  202 , in lieu of a flat ground plane in a conventional patch antenna, is that the electrical length of the heat dissipation area  206  is larger than that of a flat ground plane in a conventional design. This is possible because the electrical length of the ground plane, formed by multiple pins  208  of heat dissipation area  206 , is greater than the planar footprint of the heat dissipation area. As shown in  FIG. 2 , the electrical length of the ground plane, formed by dissipation area  206 , is provided by a bold line  214 . The length of the bold line  214  is much longer than the length of the patch  210 , which would have been the maximum electrical length in a conventional design. By increasing the electrical length of the ground plane, a physically smaller patch antenna is possible while maintaining similar antenna efficiency as in the prior art. 
   Another feature of the patch antennas  200  and  201  is an integral antenna feed structure for the patch antenna. The body of the patch  210  and an antenna feed because line  216  are fabricated as one part, unlike conventional patch antenna designs. When the patch antennas  200  and  201  are installed, the antenna feed line  216  is electrically connected to the wireless device  204 . Also, the ground plane of the patch antenna serves as the ground plane of the antenna feed structure. This integral antenna feed structure design provides a more consistent performance and a significant savings in assembly complexity and costs. 
   The wireless device  204  obtains its power from a connection  218 , its ground at a connection  220 , and its bi-directional LAN connection (Ethernet, Giga bit Ethernet, USB, etc) at a connection  222 . The wireless device  204  transmits and receives the LAN signals to and from the patch antennas  200  and  201  via the antenna feed lines  216 . By integrating the antenna areas  202 , the heat dissipation areas  206 , and the wireless device  204 , a compact design with reduced size and reduced weight is provided. 
     FIG. 2  essentially presents a fully self-contained wireless data terminal incorporating two patch antennas  200  and  201  and a wireless device  204 . The compact design achieved in this embodiment provides additional assembly cost and spatial savings without sacrificing antenna performance. The plurality of pins  208  provides two functions: the pins create an electrically larger ground plane for the patch antennas  200  and  201 , thereby allowing a smaller patch antenna size, and dissipate heat from the wireless device  204  to ambient air for cooling. The aggregate surface that provides the ground plane includes the top and side surfaces of pins  208  and the common surface of the base members from which the pins  208  extend. In addition, the heat dissipation area  206  further acts as a ground plane for the antenna feed structure. This embodiment utilizes an integral antenna feed structure combining the patch antenna body and the antenna feed line as one structure, thereby reducing the assembly complexity and assembly time. 
     FIG. 3  presents two isometric views  300  and  302  of the linearly-polarized microstrip patch antenna in accordance with one embodiment of the present invention. Pins  208  are arranged in a grid formation that is partially obscured in  FIG. 3  by the antenna patch  210 . It is understood that the isometric view  300  shows a patch antenna on one side of the wireless device  204 , while the isometric view  302  shows a patch antenna on the other side of the wireless device  204 . Views  300  and  302  may represent the front and back of a unit that includes the wireless device  204  arranged between opposed patch antennas that each include the heat dissipation area  206 , which further includes the pins  208 , the dielectric substrate  212  and the patch  210 . This embodiment results in a compact efficient design of an integrated wireless device and patch antennas. 
   The above illustration provides many different embodiments or embodiments for implementing different features of the invention. Specific embodiments of components and processes are described to help clarify the invention. These are, of course, merely embodiments and are not intended to limit the invention from that described in the claims. 
   The invention also provides an assembly method for assembling and operating the components in the described configuration to form a patch antenna assembly. Conventional coupling methods may be used. The method includes forming multiple antenna patch systems as described above, and mechanically coupling a wireless device to two antenna patch systems by joining the wireless device to the heat dissipation members and each of the antenna feed lines, the heat dissipation member directing heat from the device to ambient air and the antenna feed line electrically coupling the antenna patch and the wireless device. The method includes electrically isolating the antenna patch from the heat dissipation member by forming the antenna patch on a dielectric substrate and positioning the dielectric substrate adjacent the heat dissipation member. At least one of the wireless device and the antenna patch is operated using conventional methods and generates heat. The heat dissipation member directs the heat generated by the wireless device and the antenna patch during operation, to ambient air. The method also includes providing power to the wireless device, grounding the wireless device and providing a bidirectional LAN connection (Ethernet, Giga bit Ethernet, USB, etc). The wireless device operation may include the device transmitting and receiving LAN signals to and from the patch antennas via the antenna feed lines. 
   Although the invention is illustrated and described herein as embodied in one or more specific examples, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention, as set forth in the following claims.