A study of polarisation characteristics of targets and clutter

A transportable instrumented X-band radar was used to study copolar and crosspolar returns from targets and clutter. Recordings of these returns were made using vertical, horizontal and circular transmit polarizations. The data were analyzed to provide the relative magnitude and correlation of the copolar and crosspolar returns. Recordings from aircraft were also processed by computer simulation to study the gain obtained from combining the two channels. When linear polarization is used, the copolar signal is greater than the crosspolar signal by 9.6 dB for targets and by 6.5 dB for clutter; little is gained by combining the two returns, since the crosspolar return is on the average much smaller than the copolar channel. When circular polarization is used however, the crosspolar signal is greater than the copolar signal by only 1.6 dB for targets and by 1.8 dB for clutter; by combining the two channels, a gain of between 1 dB and 4 dB can be achieved.