Performance of offset reflector antennas with array feeds

The paper considers the radiation patterns of both single- and dual-offset reflector antennas excited by an array feed in which mutual coupling effects have been fully included. For the single-offset reflector antenna, the crosspolar pattern is dominated by the geometry of the configuration, but for a dual-offset reflector, whose geometry has been optimised to give low crosspolarisation, mutual coupling in the array becomes a dominant factor in influencing crosspolarisation. The influence of feed displacement is also reported. It is found that the change in crosspolar level is marked only for the optimised dual reflector. Then for small displacements mutual-coupling effects dominate, but for large displacements they can be neglected.