Abstract: A direct domain decomposition method(DDM) is developed to simulate bistatic scattering from a 3-D random rough surface.Coupling boundary conditions on interface between adjacent subdomains are derived as iterative Robin boundary condition(IRBC) is used as a truncation boundary in a finite element method(FEM).The final coupling matrix is obtained by an inward-looking approach.A diagonal reordering of subdomains is adopted to reduce the matrix band width.Most time consuming of IRBC computation is on large scale planar fictitious boundary above the rough surface,where the field integral equation is written in 2-D convolution form and calculated efficiently by fast Fourier transform(FFT).Our codes are examined by FEM without DDM and FEM with perfectly matched layers.

Key words: domain decomposition, finite element method, rough surfaces, electromagnetic scattering, FFT