REDUCTION OF THE GROUND REFLECTION EFFECT ON AN L-BAND POLARIMETIC ACTIVE RADAR CALIBRATOR FOR AIRBORNE AND SPACEBORNE CALIBRATION

This paper presents a technique to reduce the specular reflection effect from the ground surface to an L-band dual-polarized Single Antenna Polarimetric Active Radar Calibrator (SAPARC) with high and stable RCS (55 dBsm) by the means of using a dihedral centered at the specular point. The SAPARC uses a single antenna and a precision Ortho-Mode Transducer (OMT) to isolate between transmit and receive paths. The system is designed to achieve a 30 dB signal-to-clutter ratio while operating in free space. Degradation of such high signal-to-clutter ratio happens due to the side lobe absorption of the specular reflection from the ground. To reduce the effect of such strong reflection, it is proposed to use a dihedral positioned at the specular point on the ground covering the Fresnel zone of the SAPARC antenna. The received field is reduced by an average of 25 dB over most of angular range of interest.