The KA-MLFMA hybrid algorithm for analyzing the electromagnetic scattering from a 3-D target over random rough surface

A hybrid algorithm combining the analytic Kirchhoff approximation (KA) and the numerical multilevel fast multipole algorithm (MLFMA) is proposed to calculate the electromagnetic scattering from a composite model of three-dimensional (3-D) perfect electric conducting (PEC) object over Gaussian random rough PEC surfaces. The KA and MLFMA are used to deal with calculations of the Gaussian rough surface and the object, respectively. Meanwhile, an iterative approach is employed to analyze the coupling interactions between the object and rough surfaces. From some numerical results, it can be illustrated that this hybrid algorithm can not only give the reliable results, but also greatly reduce the computational costs comparing with conventional numerical methods. The bi-static difference field radar cross-section (RCS) of a 3-D object above random rough surfaces is also discussed in this paper.