A Study on the Isolation Capability of Multi-Beam Reflector Antennas

The paper demonstrates how multi-beam antennas used for contoured beams in communications satellites are capable of providing very high isolation to adjacent service areas, even with antenna diameters that are smaller than dictated by the normal design rule. The isolation comes at a price in coverage gain, and it is shown that there exists an isolation level beyond which the reduction in gain is dramatic whereas up to this point the gain remains fairly stable. The investigation is greatly facilitated by a new minimax optimization formulation in which the residuals are based on relative gain levels, thus avoiding absolute gain (and sidelobe) goals as in the past. One of the deficiencies in the previously used procedures is that sidelobe and coverage constraints are treated equally such that gain increase and sidelobe reduction occur simultaneously, resulting sometimes in an isolation higher than requested. The new technique can trade this extra isolation into useful coverage gain.

Publication: 1995 IEEE AP-S Symposium Digest
Place: Newport Beach, California, USA, 18-23 June, 1995