Evolution of Multiple-Beam Antenna Design for Intelsat Satellites

Abstract

An offset reflector antenna fed by a horn array feed is employed by INTELSAT to achieve multiple frequency re-use via spatial and polarization isolation among various coverage beams. As the satellites evolve from INTELSAT-V to INTELSAT-VI, the basic multiple beam antenna configuration remrains the same. However, the reflector has to be made larger due to the introduction of more zone coverage beams with closer spacing. In addition, the feed array must be refined to improve its polarizat'ion purity and expand its bandwidth; the feed network is also designed to have lower loss and be more compact. For satellites beyond INTELSAT-VI generation, the technology demand will rely on using even larger reflectors to provide zone beams separ-ated very closely.. The use of variable power dividers (VPS) and phase shifters (VPS) is very likely when a certain degree of reconfigurability is required. The feed array will require a selection between circular coniLcal horns or multi-mode horns depending on the bandwidth requirement.