ENHANCED BACKSCATTER FROM ONE-DIMENSIONAL RANDOM ROUGH SURFACES - STATIONARY-PHASE APPROXIMATIONS TO FULL-WAVE SOLUTIONS

We use the full-wave approach to obtain the solutions for the diffuse single- and double-scatter radar cross sections for one-dimensional ro ugh surfaces. The solutions are expressed in terms of two- and six-dim ensional integrals (not integral equations) for the single- and double -scatter cross sections. High-frequency, stationary-phase approximatio ns are applied to these multidimensional expressions. The full-wave, h igh-frequency approximate solutions are obtained in closed forms for t he single-scatter cross sections and in terms of two-dimensional integ rals for the double-scatter cross sections. The sharp peak in the back scatter direction is due to the contributions from the double-scatter quasi-antiparallel paths. The level and the angular width of the enhan ced backscatter peak are frequency dependent. The high-frequency appro ximations provide physical insight into the multiple-scatter problem. However, they cannot be used to predict accurately the angular width o f the backscatter peak and the polarization dependence of the scatter cross sections.