100-GHz Measurements on a Multiple-Beam Offset Antenna

Large-capacity satellite communication systems can be achieved by equipping both the satellites and earth stations with multiple-beam antennas.1 An offset Cassegrainian antenna (Fig. 1) fed by multiple, but separate, small corrugated horns has been proposed for such a system.2 Measurements and theory have indicated that the offset geometry results Fig. 1--100-GHz beam-scanning antenna. 385 ' £ **· L I* 101.3 cm f=115.6 cm 43.4 cm »> ·«] in an ideal configuration3-5 for both earth-station and satellite antennas since the aperture has no blockage; this significantly reduces the sidelobe levels and, in turn, reduces adjacent station interference. The measurements to be discussed here were obtained with a dual-mode feed horn. The current state-of-the-art needs to be pushed to its maximum potential before a satisfactory corrugated (hybrid-mode) horn at 100 GHz can be produced; utilization of a corrugated horn as a feed should further improve the performance of the scaled model discussed here.