A New Quarter Concave Cylinder Linked Dihedral Reflector for Fully Polarimetric Calibration of Wideband Nonreciprocal Radar Systems

Traditionally, fully polarimetric calibration of a nonreciprocal radar system requires measurements of at least two passive calibrators, such as a dihedral corner reflector plus a metal plate or sphere. Interchanging measurements of multiple calibrators results in not only higher complexity but also degraded uncertainty. In this work, a new polarimetric passive calibrator is proposed, which is designed as quarter concave cylinder linked dihedral (QCCLD). The backscattering of a single QCCLD contains both depolarizing and nondepolarizing components when rotating along the radar line of sight (LOS). This unique characteristic makes it an excellent polarimetric calibrator, which allows fully polarimetric calibration of a nonreciprocal radar system by measuring just a single QCCLD. The theoretical polarimetric scattering matrix (PSM) is derived based on physical optics (PO). Using complex exponential (CE) model-based parametric representation, a novel polarimetric calibration procedure is developed to suppress undesirable scattering components, which degrade the calibration accuracy. Experimental calibration results are presented with the polarization isolation improvement of more than 15 dB over 6-18 GHz frequency band, demonstrating the usefulness of the proposed QCCLD calibrator for fully polarimetric calibration of a wideband nonreciprocal radar system.