Parabolic Torus Reflector with Clustered Feed for Multibeam, High Gain, and Rapid Scanning Operations.
WASHINGTON UNIV SEATTLE DEPT OF ELECTRICAL ENGINEERING
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There is a need for high gain antennas capable of multibeam or rapid scanning operations. The use of large arrays requires costly circuitry and large parabolic dish suffers from the aberration and mechanical inertia. An attractive compromise may be the combination of a large reflector and a small number of clustered feeds. This paper presents a study on the characteristics of a parabolic torus reflector. It has an advantage of small aperture blocking, but the scanning is limited to two dimensions. First, geometric optical method is used to determine the location of the optimum source surface which minimizes the source region. It is found that when the source is located at 0.58R where R is the radius of the circle generating the torus, over 90 of rays incident on the reflector is confined on the source surface within 1 of the reflector area. Next, the amplitude and phase distributions of the source field in the focal region are investigated using the geometric optics and the surface current integration. The radiation pattern is calculated using the conjugate field on the source surface. Uniform illumination and the Taylors distribution are used and the first sidelobes are shown to be 16 db and 25 db respectively. Author
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