Electromagnetic Scattering from Multilayer Rough Surfaces Separated by Arbitrary Dielectric Profiles

Radar remote sensing of soil moisture content at low frequencies requires an accurate scattering model of realistic soils, which often involves multilayer rough surfaces and inhomogeneous dielectric profiles. In this paper, a hybrid analytical/numerical solution to two- dimensional scattering from multilayer rough surfaces separated by arbitrary dielectric profiles based on the extended boundary condition method (EBCM) and scattering matrix technique is presented. The reflection and transmission matrices of a rough interface are constructed using EBCM. The inhomogeneous dielectric profile is modeled as a stack of piecewise homogeneous dielectric thin layers. The scattering matrices of an inhomogeneous dielectric profile are computed by recursively cascading reflection and transmission matrices of individual dielectric interfaces from the bottom dielectric interface to the top interface. The interactions between the rough interfaces and the inhomogeneous dielectric profile are taken into account by applying the generalized scattering matrix technique, hi numerical simulations, the actual field-collected soil moisture data are used, hi particular, the dielectric profiles during both dry and wet ground conditions are examined. The numerical simulations are performed to investigate both bistatic scattering coefficients and copolarized phase difference due to different subsurface roughness parameters and ground conditions. Simulation results show that the bistatic scattering coefficients at low frequencies are sensitive to subsurface roughness parameters and copolarized phase difference strongly depends on soil moisture contents.