BISTATIC SPECULAR SCATTERING FROM ROUGH DIELECTRIC SURFACES

An experimental investigation was conducted to determine the nature of bistatic scattering from rough dielectric surfaces at 10 GHz. This pa per focusses specifically on the dependence of coherent and incoherent scattered fields on surface roughness for the specular direction. The measurements, which were conducted for a smooth surface with ks < 0.2 (where k = 2 pi/lambda and s is the rms surface height) and for three rough surfaces with ks = 0.5, 1.39, and 1.94, included observations o ver the range of incidence angles from 20 degrees to 65 degrees for bo th horizontal and vertical polarizations. For the coherent component, the reflectivity was found to behave in accordance with the prediction of the Physical Optics model, although it was observed that the Brews ter angle exhibited a small negative shift with increasing roughness. The first-order solution of Physical Optics also provided good agreeme nt with observations for hh-polarized incoherent scattering coefficien t, but it failed to predict the behavior of the vv-polarized scatterin g coefficient in the angular range around the Brewster angle. A second -order solution is proposed which appears to partially address the def iciency of the Physical Optics model.