New scheme for introducing an oblique incidence plane wave to layered media in finite-difference time-domain

In the application of two-dimensional finite-difference time-domain (2D-FDTD) method to the analysis of scattering by an object embedded in layered media，the obliquely incident wave along the total field-scattered field (TF-SF) contains the incidence pulse and the reflected and multiple-reflected wave，which can not be introduced by use of the traditional method. To solve this problem，a hybrid scheme using different ways to treat the four TF-SF boundaries is presented. The modified 1D-FDTD including oblique incidence angle is used to treat the longitudinal side boundaries，which can produce the reflected and multiple-reflected wave to layered interface automatically. The longitudinal side boundaries are extended downwards，such that the TF-SF lower boundary is located in the perfectly matched layer (PML) completely，thus the transmission wave and scattered wave are both outward-going waves in the lowest PML layer，and are absorbed by PML. The TF-SF upper boundary is located in free space; the incidence wave along it is in fact a properly time-delayed duplication of the waveform at the corner of TF-SF upper longitudinal boundary. The computational results show the reliability and applicability of the presented hybrid scheme.