Design for re-shaped Cassegrain antenna with offset feeds

In this paper,an efficient method is presented for correcting the phase difference due to the offset feeds illuminating the large Cassegrain antenna in which feed switch is realized by rotating its sub-reflector.Equations for solving the geometrical parameters of the new sub-reflector based on equal optical distance condition and Snell law are derived.Radiation patterns are calculated for the case with a symmetrical sub-reflector and the case with an asymmetric one.Comparisions are made between the two cases and between different offfed sizes.The results indicate this method is practical.