Bistatic Vector 3-D Scattering From Layered Rough Surfaces Using Stabilized Extended Boundary Condition Method

A model of 3-D electromagnetic scattering from multiple rough surfaces within homogeneous-layered or vertically inhomogeneous media is developed in this work. This model, aimed at radar remote sensing of surface-to-depth profiles of soil moisture, computes total bistatic radar cross sections from the multilayer structure based on the scattering matrix approach, cascading the scattering matrices of individual rough interfaces and the layer propagation matrices. We have recently developed the single-surface scattering matrix obtained using the stabilized extended boundary condition method (SEBCM) providing both large validity range over the surface roughness and higher computational efficiency compared to fully numerical solutions. In the presence of a vertical dielectric profile, the aggregate scattering matrix of the profile is obtained from the model of stratified homogeneous layers. Results of this multilayer SEBCM model are validated with small perturbation method of up to third order and the method of moments. Additionally, the model is used to perform a sensitivity analysis of the scattering cross section with respect to perturbations in ground parameters such as subsurface layer separation, roughness of surface and subsurface layers, and moisture content of subsurface layers. The multilayer SEBCM model developed in this work presents a realistic and computationally feasible method for solving scattering from multilayer rough surfaces of realistic roughness, providing an accurate and efficient tool for future retrievals of soil moisture profiles.