Cross-Polarized Planar Reflector for Polarimetric Radar Calibration at 77 GHz

In this paper, a printed circuit board (PCB)-based planar cross-polarized reflector is designed and fabricated for polarimetric radar calibrations at 77 GHz. The reflecting structure consists of a double-cladded substrate material with an etched strip grid on the front and a ground plane on the back. Initial design and parameter optimization are based on unit cell simulations. Next, a full-wave simulation of a small version of the structure is performed in order to verify the unit cell results and to consider edge effects at the boundaries of the finite surface. Finally, a 24cm × 24cm version of the optimized structure is fabricated and measured in an anechoic chamber with a fully polarimetric radar system operating at 77 GHz. The results are compared to that of a 45°-rotated dihedral. A measured cross-to co-polar isolation of 20 dB in boresight direction in the 76-78 GHz band proves the feasibility of the proposed structure.