An enhanced higher-order FDTD technique for the construction of efficient reflectionless PMLs in 3-D generalized curvilinear coordinate systems

A systematic implementation of reflectionless split and unsplit-field PMLs in 3-D nonorthogonal curvilinear coordinates via a novel higher-order FDTD methodology, is presented. The technique, which introduces both conventional and nonstandard schemes, incorporates a higher-order rendition of the covariant and contravariant vector component theory. Enhanced attenuation performance and levels of accuracy are achieved by means of new conductivity profiles and efficient ABCs terminating the PML, region. Moreover, a progressively expanding curvilinear discretization algorithm leads to a significant reduction of the absorbers' necessary thickness. In the temporal variable, the four-stage Runge-Kutta integrator is invoked, whereas the wider spatial increments near absorbing walls are effectively limited through the use of properly modified compact operators. Numerical verification demonstrates that the proposed higher order curvilinearly structured PMLs offer a considerable decrease in dispersion errors and can be imposed very close to the scatterer, thus attaining notable savings in computational resources.