Characterization of radiation boundary conditions used in the finite-difference time-domain method

When the finite-difference time-domain (FDTD) method is applied to open region scattering and coupling problems, some artificial mechanism must be used to simulate the infinite region on the necessarily finite spatial grid. The current method of choice is to use a radiation boundary condition (RBC) based on an approximate one-way wave equation. Typically, these RBCs are tested numerically. Unfortunately, using the numerical approach, it is difficult to extract precise information relating the RBC error to the frequency and angle of incidence of the outgoing wave and to the cell and time step sizes from this type of measurement. An alternate, analytic, approach to testing RBCs is presented. This approach provides a more effective means of characterizing various RBCs and comparing their accuracy in different parameter regimes. Results are presented indicating the validity of the proposed approach.<>