Abstract:
A patch array antenna is disclosed. The patch array antenna includes a ground plane with two patches. Each patch is supported from the ground plane only by metal posts. The patch array antenna further includes two-pin-feed probes, each pin-feed probe coupled to one patch, and a two-way high power divider attached to both pin-feed probes.

Description:
GOVERNMENT INTEREST 
   The invention described herein may be manufactured, used and licensed by or for the U.S. Government. 

   BACKGROUND 
   1. Field of the Invention 
   The invention is in the field of patch antennas. More specifically, the invention is in the field of two-patch array antennas. 
   2. Background of the Invention 
   An antenna is an element used for radiating or receiving electromagnetic waves. While antennas are available in numerous different shapes and sizes, they all operate according to the same basic principles of electromagnetics. 
   As a general principle, a guided wave traveling along a transmission line in an antenna will radiate free-space waves also known as electromagnetic waves. Conversely, when an antenna is receiving, it transforms free-space waves by inducing a guided electromagnetic wave within a transmission line. The guided electromagnetic waves are fed into an integrated circuit, which converts them into a useful format. 
   When an antenna is transmitting, it receives the guided electromagnetic wave for transmission from a feed line and induces an electric field surrounding the antenna to form a free-space propagating electromagnetic wave. The features of an antenna can be described by parameters of operation such as frequency, radiation patterns, reflected loss, and gain. 
   An antenna may be a component of a device such as a cellular telephone, radio, television, or RADAR system that directs incoming and outgoing radio waves between free space and a transmission line. Antennas are usually composed of metal or polymers filled with metal or carbonaceous particles and have a wide variety of configurations, from the whip or mast-like devices employed for radio and television broadcasting to the large parabolic reflectors used to receive satellite signals and the radio waves generated by distant astronomical objects. 
   Many types of portable electronic devices, such as cellular phones, GPS receivers, palm electronic devices, pagers, laptop computers, and telematics units in vehicles, need an effective and efficient antenna for communicating wirelessly with other fixed or mobile communication units, including satellites. Advances in digital and radio electronics have resulted in the production of a new breed of personal communications equipment posing special problems for antenna designers. 
   Personal wireless communication devices have created an increased demand for compact antennas. The increase in satellite communication has also increased the demand for antennas that are compact and provide reliable transmission. In addition, the expansion of wireless local area has also necessitated the demand for antennas that are compact and inexpensive. 
   Wire antennas, such as whips and helical antennas, are sensitive to only one polarization direction. As a result, they are not optimal for use in portable communication devices which require robust communications even if the device is oriented such that the antenna is not aligned with a dominant polarization mode. 
   A patch antenna is a type of antenna that offers a low profile and easy manufacturability, great advantages over traditional antennas. Patch antennas are planar antennas used in wireless links and other microwave applications. They use patches formed on the top surface of a thin dielectric substrate separating them from a conductive layer on the bottom surface of the substrate that constitutes a ground for the transmission line or antenna. 
   Reflector or dish antennas are commonly used in residential environments for receiving broadcast services, such as television channel signals from geostationary, or equatorial, satellites. Reflector antennas, however, are bulky and relatively expensive for residential use. Furthermore, inherent in reflector antennas are feed spillover and aperture blockage by a feed assembly, which significantly reduces their aperture efficiency. An alternative antenna, such as a patch antenna, overcomes many of the disadvantages associated with reflector antennas. 
   Patch antennas require less space, are simpler and less expensive to manufacture, and are more compatible than reflector antennas. A parabolic reflector antenna has a curved surface. A patch antenna can be made having a planar surface. Further, a patch antenna can achieve the concentration of an antenna beam in a particular direction by means of the application of one of several methods. 
   Patch antennas are particularly suitable for use as active antennas. An active antenna is an antenna having all of the necessary components, such as an antenna element, feeding circuits, active devices or active circuits, integrally provided on a monolithic substrate, thus producing compact, low cost, and multi-function antenna equipment. 
   Additionally, the planar structure of a patch antenna permits it to be conformed to a variety of surfaces having different shapes. Patch antennas can be designed to produce a wide variety of patterns and polarizations, depending on the mode excited and the particular shape of the radiating element used. This results in the patch antenna being applicable to many military and commercial devices, such as use on aircraft or space antennas. 
   There is an increasing demand for the use of patch antennas in wireless communication due to their inherently low back radiation, ease of conformity and high gain as compared to wire antennas. The patch antenna design prevents large amounts of radiation from being produced at the back of the antenna. 
   Patch antennas comprise one or more conductive rectilinear or ellipsoidal patches supported relative to a ground plane and radiate in a direction substantially perpendicular to the ground plane. As opposed to a conventional wire-based antenna, the patch antenna comprises a plurality of generally planar layers including a radiating element, an intermediate dielectric layer, and a ground plane layer. The radiating element is an electrically conductive material imbedded or photo etched on the intermediate layer and is generally exposed to free space. 
   Depending on the characteristics of the transmitted electromagnetic energy desired, the radiating element may be square, rectangular, triangular, or circular and is separated from the ground plane layer. An exemplary patch antenna may include a transmission line feed, multiple dielectrics, and a metalized patch on one of the dielectrics. In a typical patch antenna, the radiator element is provided by a metallic patch that is fabricated onto a dielectric substrate over a ground plane. 
   The dual-band signal-layer patch antenna has been widely used in applications like radar and communication systems because of its advantages over a conventional antenna, such as lighter weight, lower profile and lower cost. Generally, dual-band single-layer patch antennas can be categorized into categories which include stub-type patch antennas, notch-type patch antennas, pin-and-capacitor-type patch antennas, and slot-loaded-type patch antennas. 
   The patch antenna has a very low profile and can be fabricated using photolithographic techniques. It is easily fabricated into linear or planar arrays and readily integrated with microwave integrated circuits. Patch antennas are commonly produced in half wavelength sizes, in which there are two primary radiating edges parallel to one another. 
   The performance of an antenna is determined by several parameters, one of which is efficiency. For a patch antenna, “efficiency” is defined as the power radiated divided by the power received by the input to the antenna. A one-hundred percent efficient antenna has zero power loss between the received power input and the radiated power output. Factors that determine patch antenna efficiency include the loss in the dielectric material, the surface wave loss, and conduction losses. Traditional patch antennas, designed with a dielectric material, have about 80% efficiency. For example, if the patch array antenna, designed on the dielectric, is excited with an input power of 1 kilowatt, the antenna will radiate 800 watts while 200 watts are lost. 
   Patch array antennas typically rely on traveling waves and require a complex feed network which contributes significant feed loss to the overall antenna loss. Furthermore, many patch antennas are limited to transmitting and/or receiving only a linearly polarized beam. The substrate is mounted on a larger ground plane, which serves as the return path for current induced on the patch element. 
   A patch antenna operates by resonating at a frequency. The patch antenna performs optimally when it is sized such that the cavity beneath the patch resonates in its fundamental mode at the frequency of interest. 
   Therefore, it is desirable for high power patch antennas to have high efficiency. 
   SUMMARY OF THE INVENTION 
   A high efficiency, high power two-patch array antenna system can be realized by suspending the patch above the ground plane by supporting metal posts. These elements are separated at prescribed distances and the metal posts are precisely located for obtaining electrical performance in terms of antenna pattern and gain. With such a configuration, the performance of the antenna system is equivalent to a much larger horn antenna The antenna&#39;s architecture is low profile and suitable for platform integration. The design is unique, reproducible, and affordable for manufacturing a low cost system. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a back view of an antenna system of the present invention, 
       FIG. 2  is a front view of an antenna system of the present invention. 
       FIG. 3  is an exploded view of an antenna system of the present invention. 
       FIG. 3   a  is a schematic of the cover of an antenna system of the present invention. 
       FIG. 3   b  is a schematic of the s pacer of an antenna system of the present invention. 
       FIG. 3   c  is a schematic of the ground plane of an antenna system of the present invention, 
       FIG. 3   d  is schematics of a patch of an antenna system of the present invention. 
       FIG. 3   e  depicts a commercial two-way high power divider with two right angle male-to-male connectors. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 and 2  show the outside of the system  100 .  FIG. 1  is a back view of system  100 . System  100  may include an outer cover  110 . Outer cover  110  may include a hole through which a connector  120  may extend. Connector  120  may be able to be integrated with a high power RF (radio frequency) source. The high power RF source may be greater than 1 Kilowatt in power. 
   Outer cover  110  may enclose the other elements of system  100 . Outer cover  110  may be of metal, plastic, or any other material capable of enclosing the other elements of system  100 . Preferably, outer cover  110  is impervious to the environment. 
     FIG. 2  is a front view of system  100 . System  100  may include an antenna cover  230 . Antenna cover  230  is preferably made of a doped TEFLON® composition, e.g. DUROID® made by the Rogers Corporation. However, antenna cover  230  may be made of non-metallic material capable of enclosing the elements of system  100 . Antenna cover  230  may be adapted to fit within outer cover  110 . Outer cover  110  may include flanges  240 . Flanges  240  may have a plurality of holes that allow system  100  to be mounted onto a platform. 
     FIG. 3  is an exploded view of system  100 . A two-way high power divider (described below with respect to  FIG. 3   e ), a ground plane (described below with respect to  FIG. 3   c ), two patches (described below with respect to  FIG. 3   d ), and a spacer (described below with respect to  FIG. 3   b ) are all sandwiched between outer cover  110  and antenna cover  230 . A rim  350  running around the inner edge of outer cover  110  may hold all the elements in place. 
     FIG. 3   a  is a schematic of antenna cover  230 . While specific dimensions are given in the figure, antenna cover  230  can be of any dimension or shape. Antenna cover  230  may be secured to outer cover  110  using screws, rivets, bolts or other fasteners through holes in antenna cover  230 . While  FIG. 3   a  shows  10  holes, any number of screw holes may be used. Additionally, antenna cover  230  may be secured to outer cover  110  via adhesive, clips, locking devices, or any other means known in the art. The seal between the antenna cover  230  and outer cover  110  may be air-tight and/or water-tight. 
     FIG. 3   b  is a schematic of a spacer  360 . While specific dimensions are given in the figure, spacer  360  can be of any dimension or shape. Spacer  360  may be secured between antenna cover  230  and outer cover  110  using screws, rivets, bolts or other fasteners through holes in spacer  360 . While  FIG. 3   b  shows 10 holes, any number of screw holes may be used. Spacer  360  is preferably made of a thermoplastic resin, such as a polycarbonate, e.g. as LEXAN® made by SABIC Innovative Plastics. However, spacer  360  can be made of any non-conducting material, including but not limited to plastics, glass, fibers, etc. 
   Spacer  360  is positioned between antenna cover  230  and ground plane  370 . Spacer  360  has a void  365  in its center into which patches  380  may fit. Spacer  360  is preferably ½ inch high, however it can be of any height, including, but not limited to, ¼ inch, ⅓ inch, ⅔ inch, ¾ inch, and one inch. The height of spacer  360  may be chosen to minimize the loading effects of the dielectric cover on the patches. 
     FIG. 3   c  is a schematic of ground plate  370 . While specific dimensions are given in the figure, as exemplary of the best mode know to the inventor, ground plate  370  can be of any dimension or shape. Ground plate  370  may be secured between antenna cover  230  and outer cover  110  using screws or bolts through holes in ground plate  370 . While  FIG. 3   b  shows 10 screw holes, any number of screw holes may be used. Ground plate  370  may be made of any conducting material. Ground plane  370  supports two patches  380 . 
     FIG. 3   d  is a schematic of patches  380 . Patches  380  may be supported from ground plane  370  by posts. Preferably, each patch  380  may be supported by two posts located at positions  383 . However any number of posts may be used to support patch  380 . The posts may be made of metal, plastic or any other materials know in the art. Furthermore, the posts may be held in place by bolts, clips, adhesive, or any other method known in the art. Additionally, each patch  380  may be coupled to a pin-feed probe. Pin-feed probes excite patches  380  and may be coupled adjacent to an edge of patch  380  other than locations  383 , such as location  385 . 
   Patches  380  are preferably separated by a distance of 1.27864λ, where λ is the operating wavelength of system  100 . However, patches  380  may be separated by any distance, including, but not limited to, 1λ, 1.1λ, 1.2λ, 1.3λ, 1.4λ, and 1.5λ. Furthermore, patches  380  may be placed at a location separated from spacer  360 . 
     FIG. 3   e  is an image of a two-way high power divider  390  with two right angle male-to-male connectors  395 . The connectors  395  are connected to the pin-feed probes coupled to each patch  380 , 
   It should be apparent that embodiments other than those specifically described above may come within the spirit and scope of the present invention. Hence, the present invention is not limited by the above description.