Volumetric-Perturbative Reciprocal Formulation for Scattering From Rough Multilayers

We present an innovative formulation for the evaluation of the electromagnetic wave interaction with non trivial random stratifications that can include the cases of random roughnesses and volumetric inhomogeneity; the formulation is based on a volumetric perturbative approach and it is intrinsically reciprocal. The description employed to model the multilayered structure relies on a characterization of the space-variant dielectric permittivity perturbation; this approach allows us to consistently treat both interface roughness and volumetric fluctuations. Accordingly, the developed comprehensive scattering approach methodologically permits to, simultaneously and rigorously, take into account both rough-interface scattering and volume scattering. The presented first-order general formulation is then applied to the case of a layered structure with rough interfaces, but no inhomogeneities within each layer. For this case, a closed-form solution is obtained. We also demonstrate that the polarimetric solution, derived for a 3-D layered geometry and a bistatic radar configuration can be directly expressed in terms of unperturbed solutions. Our solution turns out to be formally fully consistent with the one obtained in the theoretical framework of the boundary perturbation approach. A remarkable interpretation of the analytical solution in terms of the Rumsey's reaction concept is finally provided.