Stability analysis and improvement of the conformal ADI-FDTD methods

In order to model curved conducting boundaries with high accuracy, conformal alternating direction implicit finite-difference time-domain (ADI-FDTD) methods have been developed with applications of Dey-Mittra's and Yu-Mittra's conformal techniques. We show that the conformal ADI-FDTD methods developed as such lose the unconditional stability although it is expected with the ADI schemes. We present the theoretical analysis and numerical experiments that proves our findings. We then present a modified conformal ADI-FDTD technique with better stability than those based on Yu-Mittra's and Dey-Mittra's conformal techniques.