A Convenient Technique For Polarimetric Calibration Of Radar Systems

Abstract

This paper introduces a practical technique for cal- ibrating single-antenna polarimetric radar systems. With this technique, only a single calibration target is needed to calibrate the radar system, both in amplitude and phase, for all linear po- larization configurations. By using a metal sphere, which is ori- entation independent, error in calibration measurement is min- imized, while simultaneously calibrating the cross-polarization channels. The antenna system and two orthogonal channels (in free space) are modeled as a four-port passive network and the transmit and receive channel imbalances are obtained from mea- surement of the backscatter from a metal sphere. For an X-band radar system with cross-polarization isolation of 25 dB, compar- ison of values measured for a sphere and a cylinder with theo- retical values shows agreement within 0.4 dB in magnitude and 5' in phase. Also an effective polarization isolation of 50 dB is achieved using this calibration technique.