Improved Calibration Technique for Quasi-Monostatic Polarimetric Measurement System Using a Dihedral as the Calibration Reference

The alluring polarimetric characteristics of a dihedral corner reflector make it specially useful as a polarimetric calibration reference. However, for a radar cross section (RCS) range with quasi-monostatic geometry where there exists a small bistatic angle, the polarimetric calibration error rapidly increases as the bistatic angle increases when a dihedral is used as the polarimetric calibration reference. In this work, an improved calibration technique for quasi-monostatic polarimetric measurement system is proposed. The scattering mechanism of a rectangular dihedral corner reflector in a quasi-monostatic radar system is analyzed, where the bistatic angle constrains to be within a few degrees. The polarimetric characteristic of the dihedral is evaluated by means of physical optics (POs) approximation. Combining the evaluation formulation with a nonlinear calibration technique, the polarimetric measurement error model can be adapted for the quasi-monostatic geometry so that accurate polarimetric calibration may be accomplished. The experimental results are presented to validate the proposed technique with essential improvement in the calibrated cross polarimetric measurements.