Cross polarization performance of high gain antennas in the presence of phase errors

The effects of asymmetric linear phase errors on the cross polarization of offset reflector antennas were studied. Both single TE11 mode and matched dual-mode feeds were investigated. For the former single mode feed, it was shown that the phase error significantly deteriorated the cross polarization performance with the increased non-uniformity of the phase patterns, particularly at the diagonal plane. As for the primary matched feeds, the effect of asymmetric linear phase errors, applied only to the TE21 mode, on the cross polarization of offset reflector antennas was investigated. In practice, such phase errors are the result of separate phase centre locations of each TE11 and TE21 modes. A broad range of f/D ratios were studied. It was shown that the cross polarization levels drastically increased at both inter-cardinal and asymmetry planes. More interestingly, the cross polarization pattern had a broadside shape rather than a boresight-null. The results were the same as the radome effects on the cross polarization of monopulse tracking systems were reported.