One-Step Leapfrog ADI-FDTD With CPML for General Orthogonal Grids

The unconditionally stable one-step leapfrog alternating-direction-implicit finite-difference time-domain (ADI-FDTD) method is extended and developed for general orthogonal grids in this letter. It can be derived from either the conventional ADI-FDTD but with no mid-time computation, or simply conventional FDTD, just with one perturbation term added. The convolutional perfectly matched layer (CPML) is also derived for general orthogonal grids. The proposed developments are validated and further used for investigation of the earth-ionosphere cavity, with the Schumann resonant frequencies captured. It is numerically demonstrated that the proposed method is unconditionally stable and more efficient than the conventional FDTD method for the problems considered here.