A Programmable RF-Switched Double-Antenna Transponder for Fully Polarimetric Radar Calibration

Polarimetric active radar calibrators (PARCs) are getting more and more applications in calibration of polarimetric radar systems because of their flexible operational modes and adjustable radar cross section (RCS). In this article, a new programmable radio frequency (RF) switched double-antenna PARC (SIDAPARC) is designed and implemented, which consists of a transponder using two dual-polarized antennas operated through the control of two single-pole double-throw (SPDT) RF switches. Standard reference polarimetric scattering matrices (PSMs) can be obtained by switching the polarization states of the receive and transmit channels using the two program-controlled SPDT switches. Considering the distortion of calibrator, a modified polarimetric measurement signal model for SIDAPARC is developed. A polarimetric calibration procedure based on the pre-calibration technique for SIDAPARC is proposed. The polarization crosstalk factors of calibrator can be estimated through the pre-calibration. During the calibration of a polarimetric radar system, compensating for these factors enhances the estimates of radar system distortion parameters, thus improving polarization calibration performance. Both indoor and outdoor experiments are conducted to demonstrate the usefulness of the proposed calibration procedure with more than 16-dB improvement of polarization isolation for fully polarimetric imagery.