Patent Publication Number: US-6211838-B1

Title: High efficiency dual polarized horn antenna

Description:
BACKGROUND 
     The present invention relates generally to antennas, and more particularly, to an improved high efficiency dual polarized horn antenna. 
     The closest prior art relating to the present invention known to the inventors is an antenna developed by the assignee of the present invention. This antenna had its aperture divided into four sections. This division of the antenna aperture improved the illumination efficiency from 81 percent to 90 percent compared to antenna without a divided aperture. However, this prior art antenna was limited to a two wavelength aperture. 
     Accordingly, it would be advantageous to have a high efficiency dual polarized horn antenna whose performance is further improved over the above-described four-segment divided aperture antenna, and also can be applied to large horn apertures 
     SUMMARY OF THE INVENTION 
     The present invention provides for a high efficiency dual polarized horn antenna. The dual polarized horn antenna comprises a body that is tapered from a first end to a second end such that the first end is smaller in cross section that the second end. A flange is formed around the periphery of the body adjacent the first end, and an opening is formed in the first end of the body. A tuning iris is preferably disposed at the opening that provides for impedance matching. An insert is disposed in the central tapered opening adjacent to the second end of the body that comprises a central cross-shaped tapered member. The central cross-shaped tapered member extends into the central tapered opening and forms a plurality of waveguide passages through the horn antenna that form a corresponding plurality of quadrants. A plurality of cross-shaped members are respectively disposed in the quadrants and extend a short distance into the central tapered opening. 
     The present horn antenna increases the efficiency of a square or rectangular aperture which may be used in situations where a high efficiency aperture is needed in a constrained space. The antenna may be advantageously used where larger apertures are desired. The antenna has a radiating efficiency on the order of 97 percent compared to the 81 percent radiating efficiency of an undivided aperture antenna, or the 90% efficiency of the prior art four-segment divided aperture antenna. The present invention thus provides for a dual polarized horn antenna that has higher efficiency that prior antennas and is not limited to apertures of less than two wavelenghts. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The various features and advantages of the present invention may be more readily understood with reference to the following detailed description taken in conjunction with the accompanying drawings wherein like reference numerals designate like structural elements, and in which: 
     FIG. 1 illustrates an exemplary embodiment of a high efficiency dual polarized horn antenna in accordance with the principles of the present invention; and 
     FIG. 2 illustrates an exploded view of the dual polarized horn antenna shown in FIG.  1 . 
    
    
     DETAILED DESCRIPTION 
     Referring to the drawing figures, FIG. 1 illustrates exemplary embodiment of a high efficiency dual polarized horn antenna  10  in accordance with the principles of the present invention. FIG. 2 illustrates an exploded view of the dual polarized horn antenna  10  shown in FIG.  1 . 
     The high efficiency dual polarized horn antenna  10  comprises a body  11 , which may have square or rectangular in cross-section. The body  11  is tapered from a first end  12   a  to a second end  12   b.  The first end  12   a  of the body  11  is smaller in cross section that the second end  12   b.  A flange  13  is formed around the periphery of the body  11  adjacent to the first end  12   a.  An opening  14  is formed in the first end  12   a  of the body  11 . A tuning iris  18  is preferably disposed at the opening  14  in the first end  112   a  of the body  11 . The tuning iris  18  provides for impedance matching of the dual polarized horn antenna  10 . 
     Inner side walls  15  of the body  11  define a central tapered opening  16  through the horn antenna  10 . One or more slots  17  are longitudinally formed along the length of each of the inner side walls  15 . 
     An insert  21  is disposed in the central tapered opening  16  adjacent to the second end  12   b  of the body  11 . The insert  21  is inserted into the central tapered opening  16  from the second end  12   b  of the body  11 . The insert  21  has a central cross-shaped tapered member  22  that extends into the central tapered opening  16 . The central cross-shaped tapered member  22  forms four waveguide passages  23  through the horn antenna  10  that form four quadrant  24 . The central cross-shaped tapered member  22  has a step-shaped configuration at an end thereof that is adjacent the first end  12   a  of the body  11 . 
     At the second end  12   b  of the body  11 , each quadrant  24  is subdivided into four subquadrants  24   a  by respective cross-shaped members  25 . The cross-shaped members  25  extend a short distance into the central tapered opening  16 . Thus, the exemplary embodiment of the horn antenna  10  has sixteen apertures  27  formed at the second end  12   a  of the body  11 . However, depending upon the desired application for the horn antenna  10 , it is to understood that each quadrant  24  may be subdivided into any number of sections or subquadrants  24   a  equal to 2 n , where n is real and positive, by appropriately-sectioning the respective cross-shaped members  25 . 
     The exemplary embodiment of the horn antenna  10  transforms the aperture  27  of a square or rectangular horn with its inherent 81 percent illumination efficiency into an aperture  27  with nearly uniform illumination. The efficiency of the antenna aperture  27  approaches 100 percent (97 percent) and therefore provides maximum antenna gain for this size of aperture  27 . 
     Thus, an improved high efficiency dual polarized horn antenna has been disclosed. It is to be understood that the described embodiments are merely illustrative of some of the many specific embodiments that represent applications of the principles of the present invention. Clearly, numerous and other arrangements can be readily devised by those skilled in the art without departing from the scope of the invention.