Parametric design of multiple beam reflector antennas

There has been a tremendous growth over the last few years in the use of multiple beam antennas (MBAs) for direct broadcast satellites and personal communication satellites. The MBAs provide a contiguous or non-contiguous coverage over a specified field-of-view on Earth by using high gain multiple spot beams for downlink and uplink coverage. Design of these MBAs using conventional feeds has been discussed earlier (see Rao, S., IEEE Antennas and Propagation Magazine, vol.41, no.4, p.53-9, 1999; IEEE AP-S Digest, vol.4, p.2078-81, 1998). This paper presents a parametric design approach using the horn efficiency as a variable. It is shown that the electrical performance of the MBAs in terms of coverage gain and copolar isolation can be significantly improved by selecting optimum efficiency for these multi-mode feed horns. Analytical results of the MBA with horn efficiency as parameter are presented here including comparisons with computed values.