An Approximate PML Applied to Cylindrical and Spherical Coordinate Sectors

This letter proposes an approximate perfectly matched layer (PML) that is applicable to cylindrical and spherical coordinate sectors. The proposed PML is based on complex coordinate stretching, which enables the truncation of finite-difference time-domain (FDTD) grids, not only at the ρ- and r-coordinates but also at the φ- and θ-coordinates. The absorption performance of the PML is demonstrated through numerical simulations.