A Multihybrid FE-BI-KA Technique for 3-D Electromagnetic Scattering From a Coated Object Above a Conductive Rough Surface

A multihybrid method combining numerical vector finite-element method/boundary integral method (FEM/BIM) and analytic Kirchhoff approximation (KA) is developed to study electromagnetic scattering from a 3-D coated target above 2-D conductive randomly rough surface. The hybrid vector FEM/BIM is applied to model scattering from the coated target, while the scattering from the rough surface is studied by KA, which can greatly reduce the computation time and memory requirement. An iterative approach is adopted to take into account the interaction between the target and underlying rough surface. The electric fields integral equations of the induced difference current on the rough surface and the induced electric and magnetic currents on the surface of the target are derived based on green's function and the boundary conditions. Our numerical code is validated by the commercial software. The convergence and the iteration error of the multihybrid method are discussed. Using the Monte Carlo method to generate 2-D Gaussian rough surface, bistatic difference field radar cross section of a 3-D coated sphere above a 2-D conductive rough surface is numerically simulated.