Focal region fields of dual reflector antennas

A simplified analytical method to predict the field distribution in the focal region of dual reflector antennas having circular symmetry is presented. The method is used to study the field distribution at the subdish and in the focal plane, and hence the ability of the antenna in focusing the incident wave. Experimental results obtained on a 2.6-m spherical Gregorian reflector operating at 9.0 GHz agree well with theoretical ones.