Far-field reflectometry for characterization of active antennas

Testing active antennas or polarimetric radar calibrators in the far field (plane wave excitation) is complicated by imperfect isolation between transmit and receive channels. We describe a far-field reflectometry setup which overcomes this problem. A large dynamic range is achieved by modulating the active element bias and using a quadrature receiver and lock-in detection scheme. A calibration method and a novel mixer phase-error correction scheme are described. The system is capable of full polarimetric characterization of active scatterers