To meet requirement for measurement and detection of target buried partially beneath a rough surface, rough snow surface and soil surface is simulated in model of exponential type distribution rough surface with Monte Carlo method. Wide-band composite scattering from rough soil surface covered with snow and a column with rectangular cross-section buried partially is studied using finite difference time domain(FDTD). Frequency responses of wide-band composite scattering coefficient is obtained. Wide-band composite scattering coefficients varying with root-mean-square and correlation length of rough snow surface and soil surface, type of snow, thickness of snow layer, moisture capacity of soil, geometric parameter, tilt angle and buried depth of column and incident angle of electromagnetic wave are calculated. It shows that influences of root-mean-square and correlation length of rough snow surface on wide-band composite scattering coefficient are unobvious, but influences of other parameters on wide-band composite scattering coefficient are remarkable and complex.

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.

An improvement of the vector basis functions of quadratic hexahedral edge elements is presented.After a brief review of the original hexahedral edge elements^[4],the procedure for the construction of the new edge basis functions is proposed.A better orthogonality is gained for the new basis functions,which facilitates the enforcement of Dirichlet boundary condition in the Finite Element Method (FEM).The new hexahedral edge elements is used to solve 3D scattering problem with Perfectly Matched Layer (PML).The related numerical results are carried out to testify both effectiveness and accuracy.