MMW Polarimetric Radar Bistatic Scattering From a Random Surface

This paper explores the nature of bistatic radar scattering from terrain by reporting the results of an investigation involving measurements of the hemispherical pattern of the field scattered by a random soil surface. The measurements were performed by a 35-GHz fully polarimetric radar system with transmitter and receiver modules mounted on separate rotatable arches. The acquired data were analyzed to determine the angular sensitivities of several attributes of the scattered field, including amplitudes and phase differences of the polarized scattering coefficients, and their copolarized and cross-polarized ratios. Generally speaking, the scattering pattern exhibits a weak dependence on the scattering angle thetas_s (except along the backward direction and forward specular direction), but it exhibits a strong dependence on the azimuth angle phi, particularly for the cross-polarized components. Much of the dependence is attributed to the vectorial definition of polarization in a standard frame of reference. Comparison of the measured data with calculations based on the second-order physical optics model reveals reasonable overall agreement between theory and observations (typically within 4 dB)