色散介质电磁特性时域有限差分分析的Newmark方法

根据Debye模型、Drude模型和Lorentz模型3种常见色散介质模型频域极化率的特点,利用频域到时域的转换关系jω→?/?t,将极化矢量P与电场强度E的频域关系转换成时域内关于P的二阶微分方程,其对3种色散介质模型皆适用,具有统一的形式.然后采用相比于中心差分具有更高精度的Newmark两步算法(Newmark-β-γ法)求解该方程,进而得到E→P的递推公式,再结合本构关系得到D→E的时域递推式.实现了色散介质电磁场量的时域有限差分迭代计算.数值计算结果表明该方法是适用于3种色散介质模型的通用算法,并且相比于移位算子时域有限差分方法等以中心差分为基础的离散方案具有更高的计算精度.

Newmark method for finite-difference time-domain modeling of wave propagation in frequency-dispersive medium

The complex polarizations of three kinds of general dispersive medium models, i.e. Debye model, Lorentz model, Drude model, are described by rational polynomial fraction in jω. The relationship between the polarization vector P and the intensity of electric field E in time domain is obtained by utilizing the transformation relationship from frequency domain to time domain jω→∂/∂_t. Then, the time domain second order equation is solved by using the Newmark β and γ method, which has higher accuracy than the traditional center difference method. Once the recursive formulations for E and P are obtained, the recursive formulations for D and E in time domain can be also obtained based on the constitutive relation. Therefore for a dispersive medium the iterative electromagnetic field calculation is conducted by finite-difference time-domain (FDTD) method. The present numerical results demonstrate that the proposed method is a general algorithm for three kinds of general dispersive medium models, and has higher accuracy than the shift operator-FDTD, which is based on the central difference discrete scheme.
Keywords： Newmark method dispersive media electromagnetic scattering finite-difference time-domain method