APPLICATION OF BEAM SIMULATION TO SCATTERING AT LOW GRAZING ANGLES .1. METHODOLOGY AND VALIDATION

Numerical simulations of rough surface scattering at near-grazing inci dence require very large surfaces (greater than or similar to 500 lamb da). Conventional methods of exact solutions require the inversion of a very large matrix, which can exceed the memory and speed capabilitie s of even modern supercomputers. The beam simulation method proposed b y Saillard and Maystre circumvents this problem by decomposing the lar ge incident beam into narrower subbeams and then synthesizing the larg e beam by coherent superposition. The radius of these narrower subbeam s is determined by the local interaction distance on the surface, whic h is found to increase with incidence angle, ultimately forcing a sing le beam in the limit of strict grazing incidence. This paper demonstra tes that this technique gives essentially the same results as can be o btained by the method of moments and can handle surfaces as large as 1 000 lambda for grazing incidence angle as low as 10 degrees.