Beam Scanning Characteristics of Reflector Antennas with Array Feeds

Makoto ANDO  

IEICE TRANSACTIONS (1976-1990)   Vol.E67   No.6   pp.323-330
Publication Date: 1984/06/25
Online ISSN: 
Print ISSN: 0000-0000
Type of Manuscript: PAPER
Category: Antenna and Propagation

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Excitation amplitude and phase coefficients of array elements are designed for the use of a primary feed reflector antenna with the intension of improving its beam scanning characteristics. Special attention is paid for beam isolation between two adjacent beams in an area coverage beam arrangement. After several method are compared, it is pointed out that coefficients determined in terms of aperture distribution are effective for compensating gain reduction in widely scanned angle, while they can not control beam isolation. Beam isolation, on the other hand, is effectively improved by designing array coefficients so as to arrange null points of the far field pattern on a circle with its beam direction centered. In this method, number of null points and radius of the circle are determined to get higher beam isolation. Number of null points may be set greater than that of elements, provided null points in the sense of a least mean square are also admissible. A simple parabola with offset angle of 45, fed by 9-horn array thus designed, can scan its beam beyond 10 halfpower beam width, keeping no less than 27 dB isolation between beams with spacing of about 2.0 halfpower beam width apart.