3-D scattering from buried dielectric objects beneath periodic slightly rough surfaces

Abstract

We present a hybrid semi-analytical-numerical approach that couples the Floquet Mode Matching Method (FMMM) with the Method of Moments (MoM), providing accurate analysis of three-dimensional scattering from arbitrarily shaped dielectric objects buried under periodic, slightly rough dielectric surfaces. The FMMM relies on the Rayleigh hypothesis, which is generally valid for weakly rough periodic interfaces with sufficiently small surface slopes. For two-dimensionally periodic profiles within the Rayleigh-valid regime, the Floquet expansions are obtained by numerically evaluating the required integrals using high-order quadrature. We adopt a current decomposition scheme that separates equivalent currents into background and perturbation components. This confines the MoM mesh to a limited region around the object while rigorously accounting for infinite periodic surroundings. We validate the FMMM-based surface solution against the commercial full-wave solver CST, and we validate the overall formulation using benchmark results from the literature and the commercial full-wave solver FEKO, yielding consistent agreement across all validations. Numerical experiments demonstrate the stability of the solution with respect to the perturbation region size and Floquet mode truncation. Representative radar cross-section (RCS), current distribution, and near field results illustrate the applicability of the proposed approach to subsurface scattering scenarios.