Electromagnetic scattering from a 3-D object above a 2-D rough surface by using a Bi-iteration method

A Bi-iteration model is proposed to accurately solve the composite electromagnetic (EM) scattering problem of a three-dimensional (3-D) geometrically arbitrary object above a two-dimensional (2-D) rough surface. Two iteration processes are involved in this model. Iterative physical optics (IPO) which calculates the EM scattering from the rough surface is named as inner iteration. While for the EM scattering from the composite model is computed through an iteration strategy which is named as outer iteration. The outer iteration process combines IPO and the multilevel fast multipole algorithm (MLFMA) to solve the EM scattering from the rough surface and the object. Then the mutual EM coupling interactions between them can be taken into account through this iteration process. In order to accelerate the convergence of the IPO, the forward-backward methodology is applied. Meanwhile, in order to reduce the computational time of the coupling interactions between the above object and the rough surface, local iteration methodology is applied to reduce the coupling area on the rough surface both for the inner iteration and the outer iteration processes.