A CONVENIENT TECHNIQUE FOR POLARIMETRIC CALIBRATION OF SINGLE-ANTENNA RADAR SYSTEMS

This paper introduces a practical technique for calibrating single-antenna Polarimetric radar systems. With this technique, only a single calibration target, such as a conducting sphere or a trihedral corner reflector, is needed to calibrate the radar system, both in amplitude and phase, for all linear polarization configurations. By using a metal sphere, which is orientation independent, error in calibration measurement is minimized 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. Upon using the reciprocity relations for the passive network and assuming the cross-coupling terms of the antenna to be equal, the cross-talk factors of the antenna system and the transmit and receive channel imbalances can be obtained from measurement of the backscatter from a metal sphere. For an X-band radar system with cross-polarization isolation of 25 dB, comparison of values measured for a sphere and a cylinder with theoretical 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. © 1990, IEEE.