To deal with EM simulations with the low‐frequency evanescent and propagation waves, multi‐order nearly perfectly matched layers (NPML) with complex frequency shifted factor are presented to terminate finite‐difference time‐domain (FDTD) domains. By incorporating the digital signal processing techniques including the bilinear Z‐transform, matched Z‐transform, and direct Z‐transform methods, the proposals can not only obtain better performance compared with the original NPMLs but also have considerable efficiency compared with other multi‐order PMLs. Meanwhile, these implementations can terminate arbitrary mediums without changing the field‐updated equations in the PML regions. Based upon the multi‐order concept, the proposals can be switched flexibly between the first order and multi‐order according to different EM simulations by changing the optimized parameters. Numerical results indicate that our proposals can not only enjoy higher computational efficiency but also easier to implement according to different mediums in the EM modeling and simulations.

中文翻译：

---

用于EM仿真的材料无关的多阶近乎完美匹配的层的不同实现

为了处理低频van逝波和传播波的EM模拟，提出了具有复杂频移因子的多阶近乎完美匹配的层（NPML），以终止有限差分时域（FDTD）域。通过合并包括双线性Z变换，匹配Z变换和直接Z变换方法在内的数字信号处理技术，这些提案不仅可以比原始NPML获得更好的性能，而且与其他多阶MLML相比也具有相当高的效率。 PML。同时，这些实现可以终止任意介质，而无需更改PML区域中的字段更新方程。基于多阶概念，通过更改优化参数，可以根据不同的EM模拟在第一阶和多阶之间灵活切换建议。数值结果表明，我们的建议不仅具有较高的计算效率，而且在电磁建模和仿真中根据不同的介质更易于实现。