A Dual-Dihedral Carved on Cylinder Reflector for Wideband Polarimetric Radar Calibration

Conventionally, achieving full polarimetric calibration for nonreciprocal radar systems depends upon measurements from no fewer than two passive calibrators, to obtain three linearly independent reference polarimetric scattering matrices (PSMs). Interchanging measurements of multiple calibrators result in increased uncertainty as well as higher complexity in implementation. In this study, a novel passive polarimetric calibrator, namely, the dual-dihedral carved on cylinder (DCC) reflector is proposed. When rotating over −180° to +180° azimuth angle, the backscattered field of a single DCC provides three main scattering components (MSCs), from the 0°-right cylinder, 112.5°-dihedral corner reflector, and −112.5°-dihedral corner reflector, locating at 0°, +112.5°, and −112.5° azimuth angles, respectively. This characteristic facilitates the realization of full polarimetric calibration for nonreciprocal radars through the use of a single passive calibrator. A closed-form expression of the theoretical PSM for the proposed calibrator is derived using physical optics (PO), and its full-polarization scattering characteristics are thoroughly examined. A polarimetric calibration procedure with the DCC calibrator is developed, where a kernel function matching (KFM) algorithm is used to locate the exact azimuth angle positions of the three MSCs, while a parametric representation approach based on complex exponential (CE) model is utilized to extract their corresponding PSMs from the wideband measurements. Indoor and outdoor experimental measurements for wideband PSM imagery are conducted, demonstrating an enhancement in polarization isolation of about 15 dB across the 8 to 18 GHz frequency range, validating the proposed DCC calibrator in enabling full polarimetric calibration for wideband radars.