Study On Transmission And Scattering Based On Two-Dimensional Finite-Difference Frequency-Domain Method

With the development of computational electromagnetics,the finite-difference frequency-domain method(FDFD)has been attracting attention as a traditional frequency domain numerical method.The FDFD method should be the easiest to understand method in all electromagnetic field numerical methods.There are great advantages in dealing with resonance problems,solving single-frequency point problems,dealing with dispersive media problems and dealing with oblique incidence problem of periodic structure.Due to the complexity of matrix solving,two-dimensional FDFD method is currently widely studied.In this thesis,the transmission and scattering based on the two-dimensional FDFD method are investigated.Deducing the matrix form of two-dimensional FDFD equation by briefly introducing the basic theory of finite-difference method,the mode characteristics of double-ridged metal rectangular waveguide is simply studied to verify the feasibility of finite-difference method.After deriving the matrix form of the two-dimensional FDFD equation,further research on transmission and scattering based on two-dimensional FDFD method.Transmission studies mainly include simulation of the propagation of point source and plane wave source by two-dimensional FDFD method and simulation of reflectance and transmittance of dual-layer metallic wire grids broadband polarizers.The scattering study mainly discusses the spatial field intensity distribution of metal cylinder and metal sector cylinder excited by the total-field/scattered-field plane wave source.The main work of this paper includes:1 The basic theory of finite-difference method is carefully understood,the research status of FDFD method is fully investigated and the advantages of FDFD method in solving special electromagnetic problems are clarified.2.In order to verify the feasibility of the finite-difference method,the mode characteristics of the double-ridged metal rectangular waveguide is studied,drawing the dispersion characteristic curves of the main mode,the first-order mode and the second-order mode of the waveguide.The Maxwell's equations in the frequency domain and the perfectly matched layer absorption boundary conditions are coupled to derive the final two-dimensional FDFD equations matrix form.3.Research on the propagation of point source and plane wave source based on two-dimensional FDFD method,furthermore,the spatial field distribution of metal cylinder and metal sector cylinder excited by the total field/scatter field plane wave source are discussed.4.Further research on the transmission based on two-dimensional FDFD method,a dual-layer metallic wire grids broadband polarizers is designed.The optical reflectance and transmittance of three periodic gratings(40nm,80nm,160nm)after TM wave incident on dual-layer metallic wire grids broadband polarizers are mainly studied,considering the normal and oblique incidence of TM wave.