Semi-Active Multimatrix Reflector Antennas

Abstract

ABSTRACT This paper covers recent work on a novel concept for multibeam transmit reflector antennas, called semi-active antennas since the feed array elements are not directly connected to the power modules, as in an active antennas, but separated from them by several multiport hybrid couplers. By controlling the phase of the low level equi-amplitude signals at the inputs of the amplifiers, these can be directed to selected feeds in the focal area of the reflector to generate multiple fixed or movable pencil or shaped beams. More or less channels can be routed into the beams by low level switching at the beam forming network input ports. Under all beam pointing and beam loading conditions, all amplifiers operate at nominal power, therefore with optimum efficiency. The basic principle of this new antenna architecture is presented and discussed and designs are evaluated for regional and global coverage satellite applications.