Study Of Dispersive Medium In FDTD

Materials in natural is usually frequency varying or dispersive.This paper, it makes a deep research on electromagnetic scattering of dispersive medium with digital signal processing technology and Finite-Difference Time-Domain (FDTD) method.First, this paper simply introduces the FDTD theory and three commonly-used dispersion models,and then puts forward to three novel kinds and analyzes their constitutive relations in theory. These six available dispersion models are fitted to natural electromagnetic materials in order to study electromagnetic scattering problems.Secondly, this paper introduces dispersive FDTD Z-transform based and Shift Operator (SO) based dispersive FDTD algorithms for stair approximate tessellated case. Z-transform FDTD algorithm transforms frequency-domain constitutive relation of dispersive medium into Z-domain, in which FDTD time differential operator can be discretized. SO-FDTD algorithm transforms time-differential operator to discrete time-domain shift operator to establish the constitutive relationship. It can take full advantage of FDTD theory to analyze complex dispersive medium models.Finally, the paper improves the stair tessellated SO-FDTD to conformal algorithm which averages electromagnetic parameters on target boundaries and can be more accurate in most case. Numerical examples are given to verify the correctness of the two dispersive FDTD algorithms, With suitable operating conditions, the conformal SO-FDTD algorithm has better accuracy than that of commercial dispersive FDTD algorithm.