完全匹配层(PML)吸收边界条件的理论分析

Theoretical Analysis on the Perfectly Matched Layer (PML) Absorbing Boundary Condition

本文以屏蔽微带线为例,应用谱域方法推导了时域差分(FDTD)法中所用的完全匹配层(PML)吸收边界条件的公式,并且严格证明了有关参数的选择原则.计算表明,在屏蔽微带线中,这种吸收边界条件的反射系数可以小于-80dB.本文所给出的推导方法对于平面分层介质结构是普遍适用的,因为谱域中的每一个波谱实际上都代表一个平面波.文中所给出的推导揭示了这种吸收边界条件的机理,它对于正确使用以及进一步改进这种吸收边界条件都是有意义的.

Taking the shielded microstrip line as an example, this paper gives the derivation of formulas of perfectly matched layer (PML) boundary condition by using the spectral domain method. The principle on the determination of the related parameters is also illustrated theoretically. The computational results show that the reflection coefficient caused by PML boundary condition may be lower than - 80dB. In spectral domain, each spectrum represents a plane wave, therefore, the derivation given in this paper is general for an arbitrary microstrip structure and may give the insight on the absorbing mechanism which is significant to the application and improvement of this kind of absorbing boundary conditions.