Enhanced backscatter from one-dimensional random rough surfaces: stationary-phase approximations to full-wave solutions

Abstract

We use the full-wave approach to obtain the solutions for the diffuse single- and double-scatter radar cross sections for one-dimensional rough surfaces. The solutions are expressed in terms of two- and six-dimensional integrals (not integral equations) for the single- and double-scatter cross sections. High-frequency, stationary-phase approximations are applied to these multidimensional expressions. The full-wave, high-frequency approximate solutions are obtained in closed forms for the single-scatter cross sections and in terms of two-dimensional integrals for the double-scatter cross sections. The sharp peak in the backscatter direction is due to the contributions from the double-scatter quasi-antiparallel paths. The level and the angular width of the enhanced backscatter peak are frequency dependent. The high-frequency approximations provide physical insight into the multiple-scatter problem. However, they cannot be used to predict accurately the angular width of the backscatter peak and the polarization dependence of the scatter cross sections.