Abstract:
The present invention is a single or multiple non-resonant slot antenna where said slots are formed from a continuous upward extension of the conducting ground plane with lateral horizontal planar extensions to form a top plane defining said slots.

Description:
This application claims benefit and priority of and is a continuation in part of a provisional application with Ser. No. 61/046,027 filed on Apr. 18, 2008, titled “Ground Surrounded Non-Resonant Slot-Like Patch Antenna”. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to ground surrounded patch antenna or to the general field of non-resonant slot-like antennas. 
     BACKGROUND OF THE INVENTION 
     Electromagnetically coupled patch antennas have been long known in the art. In this technical field, a parasite resonant element and an exciting element (exciter) combine to produce the desired transmission and reception functions.  FIG. 1  shows a prior art proximity coupled antenna  10 . The exciting element  11  is located at a ground surface and is connected to a signal source via a connector. A radiating element or parasitic element  12  is spaced at distance above the exciter  11 . Exciter  11  is secured to the surface of the ground plane  13  function as a primary and secondary transformer adapted to act as a doubly tuned circuit. 
     Electromagnetically coupled patch antennas can be used in general broadband broadcast and reception with high gain. However, the secondary element  12  must be elevated above the ground plane  13  and must not share any effective connection. It is difficult to maintain a required separation distance in environments where severe physical vibration or shock will affect the antenna. 
     U.S. Pat. Nos. 5,400,040 and 5,337,066 disclose patch antenna structures where all elements are substantially located upon a single planar surface to accommodate use in environmentally difficult locations. U.S. Pat. Nos. 4,907,006 and 5,200,756 disclose a parasitic element which descends to the level of a ground plane. U.S. Pat. No. 5,929,812 discloses parasitic elements short circuited to a ground plane. While the prior art contains certain disparate attempts to provide a rugged patch antenna, such prior art patch antennas are still constructed in a manner in which vibration and shock will tend to cause decreased performance over time. 
     There is a need for an antenna with identical or superior performance for placement in severe environments without adverse effects. 
     SUMMARY OF THE INVENTION 
     The present invention is a single or multiple non-resonant slot antenna where said slots are formed from a continuous upward extension of the conducting ground plane with lateral horizontal planar extensions to form a top plane defining said slots. 
       FIG. 2  shows the antenna of  FIG. 1  but adding illustration of the presence of the electric field  13 A in the substrate of a patch antenna  10 . Note that the electric field is zero along a line  14  in the middle of the patch antenna  10 . This null line suggests that if the patch antenna  10  is connected to the ground plane at a point on this line, it will not perturb the field significantly, thereby indicating an ideal set of locations for supporting elements from the ground plane  13 . This support connection will also improve the radiation performance of the patch by shorting some spurious current modes on the patch. 
     Therefore, the first step in designing the current invention is to ground the antenna at two side locations as shown in  FIG. 3  at pins  15 . This support and electrical connection makes the whole radiating element  12  and ground plane  13  perform as one radiating conductor as shown in the present invention in  FIG. 4 . 
     In the invention, a radiating surface is elevated above, electrically connected with, and supported from a peripheral metallic or conducting base. A structural combination of a radiating element and a part of a ground plane is achieved in the invention patch antenna with a dramatically different structure, i.e., a perimeter forming a structural base and extension of a ground plane rises in a center portion to support a radiating element by relatively narrow supports within non-resonant slots. 
     A partial peripheral gap or slot about the radiating element is similar to radiating slots of a slot-type antenna. In the invention antenna, the partial peripheral gap, in contrast to prior art radiating slots, are non-resonant and do not form part of the radiator. The radiating element is surrounded by a ground plane. This has been verified by providing an exciter underneath the radiating element. The gap or slot is optionally be filled with a dielectric material as required by the application. 
     It is an object of the invention to provide a rugged antenna formed to be used in rough environments. The exciting element and a complementary part of the ground plane can be connected to the underside of a cavity formed under a central part of the elevated section as shown in  FIG. 5 . 
     This form of antenna element can be used as a basic element of a planar array to form a larger aperture for increased gain. Multiple radiators can be fed by one exciter as shown in  FIG. 6 . Another embodiment includes a single radiator with multiple exciting elements to form dual polarized antennas circular antennas or improve the impedance matching or connect to several sources. 
     This concept can be used to design low profile circularly polarized by using several radiators and excite them appropriately to form a radiating circular wave. 
     Another embodiment of the invention antenna is a multi-frequency version which one skilled in the art of antenna design can design variances to this antenna and base it on this invention similar to basic microstrip antennas. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a traditional electromagnetically fed patch antenna, where an exciter connected to a source of energy is coupled to the radiating element through the exciter. 
         FIG. 2  shows the electric field distribution in the substrate of a patch antenna. The field is zero along a line in the middle of the patch. 
         FIG. 3  shows grounding connections of the patch antenna at two locations along the zero-field line on the patch. 
         FIG. 4  shows the current invention which is a one piece metal which forms the radiator and ground plane. 
         FIG. 5  shows the cross section  19   a  of ground surrounded non-resonant slot-like patch antenna in  FIG. 4 . 
         FIG. 6  shows a two element configuration of the current invention fed by one exciter. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention is now discussed with reference to the figures. 
       FIG. 1  shows a well known prior art electromagnetically fed patch antenna as described above.  FIG. 2  shows the electric field  13 A distribution in the substrate of a patch antenna  10  with a radiating element  12  elevated above a ground plane  13 . The field  13 A is zero along a null line  14  in the middle of the patch. The invention antennas are constructed to form a structurally rugged perimeter base rising in a center portion to create an elevated section co-planar with one or more radiating elements rigidly supported above and electromagnetically driven by an exciting element directly connected to a signal source. The structurally strong supports connecting the radiating elements to the elevated ground plane are co-linear with the zero or null line established by the interaction of the exciting element with the radiating element. This combination provides an almost indestructible cover for the exciting element located within a cavity formed beneath the radiating element. The perimeter base, elevated section and radiating element are formed as a single continuous piece of conductive material appropriate for the objects of the invention, such as copper or alloys thereof. 
       FIG. 3  is a generalized model for grounding and electrically effective support of the radiating element  12  from the ground plane  13 . Grounding pins  15  support the radiating element  12  at two locations along the zero-field line on the patch. The effect of such grounding is to form a substantially different antenna than that shown in  FIG. 1 . 
       FIG. 4  shows a single element antenna  16  of the invention. It should be appreciated that piece  17  is a single structurally formed piece comprising a ground plane section  20 , transition  22 , elevated section  21 , zero line supports  20 B, and radiating element  20 A, where non-resonant slots  18  are defined by edges of the radiating element  20 A, zero line supports  20 B and elevated section  21 . Ground plane section  20  and radiating element  20 A are functional equivalents of the radiating element  12  and an outer part of ground plane  13  of  FIG. 3 . 
     Referring again to  FIG. 4 , radiating element  20 A and ground plane section  20  are vertically spaced apart and horizontally parallel. Radiating element  20 A is rigidly supported by zero line supports  20 B substantially narrower than radiating element  20 A above a single exciting element (not shown), thereby forming zero line supports at two planar connections for radiating element  20 A along the electrical field zero line, which lies along cross section  19  line. Ground plane section  20  surrounds and peripherally transitions up at stepped transition  22  to the elevated section  21 . Non-resonant slots  18  generally have an appearance of resonant slots in the prior art but are very different in this embodiment of the invention. Non-resonant slots  18  must be non-resonant to the resonant frequency of the typically narrow band of the invention antenna. Radiating element  20 A, zero line supports  20 B and a part of the elevated section  21  have undersides defining a cavity beneath piece  17  for rigid and secure attachment of an exciting element and a complement section of a ground plane. Screw holes  35  are formed in ground plane section  20  to provide for immediate attachment of antenna  16  to an appropriate surface. It is apparent from inspection of antenna  16 , which is drawn to scale, that its structural strength is superior to the patch antenna structures described in the prior art. 
       FIG. 5  shows cross section  19   a  of  FIG. 4 . Patch antenna  16  further comprises a complementary ground plane section  24  structurally and electrically connected to piece  17  via two or more connection pins  23 , an exciting element  25 A connected to a signal source via a connector  26  and which is electrically insulated from radiating element  20 A and ground plane sections  20  and  24  by dielectric fill sections  18 A and  25 . It will be appreciated that radiating element  20 A, zero line supports  20 B and a part of the elevated section  21  have undersides defining a cavity beneath piece  17  within which to secure complementary ground plane section  24  and exciting element  25 A by way of pins  23  and dielectric fill sections  18 A and  25 . Causing piece  17  to be secured to a flat surface by way of the screw holes or other attachment means further encases otherwise sensitive exciting element  25 A to be secured as substantially a single, structurally secure unit adapted to survive with full functionality in an environment of severe vibration and shock. It will be appreciated that complementary ground plane section  24  is substantially rectangular and parallel to radiating element  20 A, section  24  also defining a central opening for passage of connector  26  to exciting element  25 A. 
       FIG. 6  shows a two element antenna  27  of the current invention fed by one exciting element (not shown, but similar in structure and location beneath the radiating elements as the structure shown in  FIGS. 4 and 5 ). Ground plane section  28  surrounds transition  29  to elevated section  30 , which provides zero line supports  30 B to two radiating elements  30 A, which in turn define non-resonant slots  31  and  32 . 
     The above design options will sometimes present the skilled designer with considerable and wide ranges from which to choose appropriate apparatus and method modifications for the above examples. However, the objects of the present invention will still be obtained by that skilled designer applying such design options in an appropriate manner.