Implementation of Absorbing Boundary Conditions Based on the Second-Order One-Way Wave Equation in the LOD- and the ADI-FDTD Methods

This letter describes the implementation of second-order one-way wave-equation absorbing boundary conditions (ABCs) in two unconditionally stable finite-difference time-domain (FDTD) methods-namely the locally one-dimensional (LOD)- and the alternating-direction implicit (ADI)-FDTD methods. The Higdon second-order absorbing operator is discretized in the same way as when it is used with the conventional FDTD method. The resulting discrete expression is directly applied to the electric field in each time substep of the LOD- and the ADI-FDTD methods. Numerical examples are given to illustrate the validity of the proposed approach.