完全匹配层产生数值反射的原因分析

完全匹配层是目前电磁场数值计算中比较理想的吸收边界，它对任意频率、任意入射角的电磁波的理论反射系数都为零。但由于数值离散的原因，完全匹配层边界仍然会产生一定的数值反射。本文通过理论分析，发现真空-PML和PML-PML交界面两边电导率的突变所引起的电场磁场衰减指数的突变是数值反射产生的根源。数值模拟结果表明，通过调整交界面上介电常数和电导率的取值可以有效地降低数值反射。

Analysis of the Numerical Reflection from the Perfectly Matched Layer

Perfectly matched layer (PML) is currently the most ideal absorbing boundary condition for electromagnetic field numerical simulations. The theoretical reflection from PML is always zero for any electromagnetic waves regardless of frequency and incidence angle. But in discretized space, the numerical reflection is unfortunately nonzero. It is found that the abrupt changes of the electromagnetic field attenuation index, which are caused by the abrupt changes of conductivity on the vacuum-PML interface and PML-PML interface, result in the numerical reflection. The simulation results show that the numerical reflection can be reduced by regulating the values of the permittivity and the conductivity on the interfaces.