Effect of feed cross-polarization on the cross-polar characteristics of a shaped dual reflector antenna

The two common forms of shaped reflector antennas for linear polarization applications are the dual gridded reflector antenna (with two orthogonally polarized surfaces) and a dual reflector antenna with a single surface main reflector and a single surface subreflector. The superior cross-polar performance in a dual gridded reflector is obtained by a combination of the polarizing grid and the separation between the feeds for the two polarizations. In this configuration the feed cross-polarization has a second order effect on the overall cross-polar performance. In a dual reflector antenna, the geometry inherently results in a low cross-polar performance if it satisfies the optimum cross-polar condition. Since the reflector induced cross-polarization is very low, the feed cross-polarization has a significant effect on the overall antenna cross-polar performance. This paper describes the effect of feed cross-polar performance on the antenna cross-polar performance of a shaped dual reflector antenna.