脉冲源激励下地下目标的电磁散射分析

Analysis of Transient EM Scattering from Underground Targets with Pulse Excitations

本文分析在地面上放置冲激函数源情况地下电磁场的传播和散射特性 .在冲激函数源的后期由于电磁场变化较缓慢位移电流可以忽略 ,扩散特性占据优势 .本文通过在准静态Maxwell方程中引进虚拟位移电流项 ,将扩散问题的求解转化为波动问题 ,从而应用非均匀时域有限差分 (FDTD)方法来分析地下问题 .

We enhance the FDTD method for simulating transient EM surveys of underground objects, in which impulse excitations are laid on the ground surface and the electromotive force (EMF) is measured along the ground surface. In the late time of impulse excitation, the displacement current can be neglected because of slow variation. The diffusion characteristic dominates the electromagnetic process under ground. In order to apply the FDTD method to treat the underground problem, we introduce an artificial displacement current term in the diffusion equation. Examples given demonstrate the efficiency of presented scheme.