A study of terrain scattering physics

Abstract : This report presents results of a study to improve existing models for scattering from rough terrain. The two-scale composite surface model is first corrected to properly account for shadowing. This correction shows that both the optical and Bragg scattering terms in the expression for sigma degree go to zero as grazing incidence is approached. The shadowing function for non- Gaussian surfaces is shown to be easily obtained from existing theories and numerical results for exponentially distributed surfaces are presented. The two- scale composite surface based upon the Burrows perturbation theory is extended to the following cases: bistatic scattering from a dielectric surface with small scale roughness, and bistatic scattering from a dielectric surface with large and small scales of roughness. Comparisons are made with the Rice theory for both cases. It is shown how an existing theoretical relationship between the height and slope probability density functions can be used to practically obtain one from the other. Finally, a new integral equation is developed for the coherent field scattered from a perfectly conducting rough surface. Asymptotic evaluation of this equation in the limit of large Rayleigh parameter indicates that surface slopes cannot be ignored. (Author)