Ground station antenna crosspolarisation measurements with an imperfectly polarised ancillary antenna

A technique is developed for measuring the crosspolarization radiation patterns of linearly polarized, frequency reuse satellite ground station antennas, using a satellite as the remote source. The imperfect satellite wave is sampled with a high polarization purity ancillary antenna, and a correction factor is applied to the measured crosspolarization levels. It is found in practice that the ancillary antenna may have a small but finite crosspolarization level, and error levels due to this factor are examined. Error level expressions are presented, and some typical results are evaluated.