A numerical study has been performed to examine the effects of surface self-shadowing on the electromagnetic backscattering from dielectric interfaces with two-scale roughness in one dimension. A hybrid numerical technique combining the moment method (MM) and geometrical theory of diffraction (GTD) was used in the numerical calculations. This technique was first extended to be applicable to general dielectric media as well as perfectly conducting and highly conducting, high permittivity surfaces. The numerical calculations show that, for the onedimensional (1-D) rough surfaces considered, the contribution of shadow-region roughness to vertically polarized backscatter decreases significantly as the scattering surface is changed from perfect to finite conductivity, while little change is observed at horizontal polarization. A geometrical optics (GO)-based shadowing function should be accurate down to approximately the same illumination grazing angles at both polarizations with scattering surfaces with complex dielectric constants equal to and below (in magnitude) that of sea water at microwave frequencies. At the smallest grazing angles, weakly shadowed roughness can significantly increase the backscatter from finite-conductivity surfaces at both polarizations, thereby invalidating the concept of a distinct shadow boundary. Vertical polarization is further limited by the contributions of deeply shadowed roughness that decreases with decreasing dielectric constant. As the grazing angle decreases, the shadow-corrected two-scale scattering model loses accuracy well before the contribution of the shadow-region roughness becomes significant.Index Terms-Bragg scattering, electromagnetic scattering by rough surfaces, moment methods.
A numerical study has been performed to examine the effects of surface self-shadowing on the electromagnetic scatter from rough dielectric interfaces. A hybrid numerical technique combining the moment method and geometrical theory of diffraction was used in the numerical calculations. This technique was first extended to be applicable to general dielectric media as well as perfectly conducting and high loss, high permittivity surfaces. The numerical calculations show that weakly shadowed small-scale roughness can contribute significantly to the backscatter at extreme grazing angles. This effect is more pronounced at VV polarization than at HH polarization when the surface is perfectly conducting, but is approximately the same at both polarizations when a finite-conductivity interface is considered. Scattering models that depend on a shadowing function based on geometrical optics are likely to fail at extreme grazing angles for lossy dielectric as well perfectly conducting scattering surfaces.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.