Study On The Scattering Field Of Random Rough Surface Based On FDTD

In order to better study the characteristics of the common layered phenomena,it is necessary to study the backscattering characteristics of the underlying surface in the layered rough surface.In this paper,the finite difference time domain(FDTD)method based on convolution perfectly matched layer(CPML)is used to calculate the scattering characteristics of multi-layer random rough surfaces.From the perspective of time domain,the scattering characteristics of homogeneous medium random rough surfaces and multi-layer random rough surfaces are analyzed.(1)Two kinds of absorbing boundary conditions in FDTD method,namely the uniaxial perfectly matched layer(UPML)absorbing boundary condition and CPML absorbing boundary condition,are studied.The qualitative comparison between the two absorbing boundary conditions is made.The advantages of applying CPML absorbing boundary condition to FDTD method compared with UPML method are analyzed,and CPML boundary is selected as the absorbing boundary condition in this study.The total field boundary condition and extrapolation boundary condition of FDTD program are introduced in detail,and the correctness of FDTD program based on CPML absorbing boundary condition is verified.(2)The far-field extrapolation formula of the incident time harmonic field is derived in detail.On this basis,the two-dimensional half space FDTD program is compiled and verified.The FDTD calculation models of two-dimensional single-layer random rough surface and two-dimensional double-layer random rough surface are given.The realization algorithm of each module in the model is introduced in detail.FDTD program is used to simulate the rough surface with different system parameters and random rough surface parameters and analyze the results.(3)The FDTD calculation model of single-layer three-dimensional random rough surface is given,the realization method of three-dimensional half space FDTD algorithm is given,and the use steps of FDTD program are introduced in detail.The FDTD program is used to simulate the random rough surface with different roughness parameters,and the simulation results are compared with the results obtained by the improved integral equation model(AIEM)to verify the correctness of the algorithm.On this basis,the influence of frequency,roughness parameters and dielectric constant on the backscatter coefficient of 3D random rough surface is analyzed in detail.(4)The multi-layer random rough surface model is introduced into FDTD calculation space.The backscatter coefficients of two-layer and three-layer random rough surfaces are calculated by FDTD method.By setting different roughness parameters of underlying surface,the influence of different roughness parameters of underlying surface and model related parameters on the scattering coefficients of multi-layer random rough surface is analyzed.