Polarization diverse phase dispersionless broadband antenna

Abstract

A multi-octave bandwidth antenna is disclosed which radiates with variable polarizations using: a metal ground plane, first and second blade antenna elements, first and second coaxial transmission line feeds, and a 180 DEG hybrid coupler. The two blade antenna elements are fixed above the metal ground plane in proximity with each other, and fed respectively by the central conductors of the first and second coaxial transmission line feeds. The 180 DEG hybrid coupler has a sum and difference port to control the polarization of waveforms of the antenna.

What is claimed is: 
     
       1. An antenna comprising: a metal ground plane;   first and second blade antenna elements fixed in proximity with each other above said metal ground plane;   first and second coaxial transmission line feeds each having a central conductor respectively connected to the first and second blade antenna elements; and   a means of feeding signals with controlled phase into said first and second coaxial transmission line feeds.   
     
     
       2. An antenna, as defined in claim 1, wherein said first and second blade antenna elements each comprise: a blade element which has a throat, a mouth, and a tip, said throat serving as a feed point and being electrically connected to a central conductor of one of said first and second transmission line feeds, said throat being comparatively narrow compared to other portions of the blade element, said mouth being a mid-section of said blade element and also the blade element's widest section, said tip being an arc of constant radius, said tip thereby resulting in a low voltage standing wave ratio of about 1.119 to 1.   
     
     
       3. An antenna, as defined in claim 2, wherein said means of feeding signals comprises a 180° hybrid coupler which is electrically connected with said coaxial transmission line feeds, said 180° hybrid coupler having a sum and difference port such that when a single radio frequency signal is fed into the sum port, the first and second blade antenna elements are fed in phase and a vertically polarized waveform results, when a single radio frequency signal is applied to the difference port, the first and second blade elements are fed in antiphase (180° out-of-phase) and a horizontally polarized waveform results, and when a same radio frequency signal is applied to both the sum and difference port, a 45° linearly polarized waveform results. 
     
     
       4. An antenna, as defined in claim 3, wherein said antenna includes an array of first and second blade antenna elements fixed in proximity with each other above said metal ground plane, and fed with a plurality of first and second coaxial transmission line feeds. 
     
     
       5. An antenna, as defined in claim 4, wherein said first and second blade antenna elements each has a length of about twenty two inches, a mouth width of about seven inches, and a width of about 0.1 inches.