An Efficient Multiregion FEM-BIM for Composite Scattering From an Arbitrary Dielectric Target Above Dielectric Rough Sea Surfaces

An efficient multiregion hybrid method of the finite element method (FEM) combined with the boundary integral method (FEM-BIM) is first proposed for the fast simulation of 2-D scattering from an arbitrary dielectric target above a “Pierson- Moskowitz” rough sea surface. In the implementation of the multiregion hybrid method, the entire model is divided into multiple computational regions depending on energy distribution of an incident wave. With mutual coupling between the target and the dominant region of the sea considered, FEM and BIM are respectively applied to study the target and the dominant region to exactly obtain electromagnetic fields and currents, which have powerful illuminated field and strong interaction with each other. Mutual coupling between different subordinate regions is approximately considered by field integral equations based on Kirchhoff approximation by which the approximate currents in subordinate regions can be obtained. Because FEM and BIM are only performed on the target and the dominant region of the sea, the number of unknowns and the time required in the new method are dramatically reduced than those in the traditional FEM-BIM, making the hybrid method more efficient in the simulation of the composite problem.