Modification of Classical SPM for Slightly Rough Surface Scattering with LowGrazing Angle Incidence**The project supported by NationalNatural Science Foundation of China under Grant No. 60101001 andthe National Defense Foundation of China

Abstract

Based on the impedance/admittance rough boundaries,the reflection coefficients and the scattering cross sectionwith low grazing angle incidence are obtained for both VV andHH polarizations. The error of the classical perturbation methodat grazing angle is overcome for the vertical polarization ata rough Neumann boundary of infinite extent. The derivation ofthe formulae and the numerical results show that the backscatteringcross section depends on the grazing angle to the fourth powerfor both Neumann and Dirichlet boundary conditions with low grazingangle incidence. Our results can reduce to that of the classicalsmall perturbation method by neglecting the Neumann and Dirichletboundary conditions.