Elimination of spurious solutions associated with exact transparent boundary conditions in FDTD solvers

An analysis of spurious solutions that often plague finite-difference time-domain solvers supplemented with certain transparent boundary conditions (TBC) is presented. It is shown that the electric- and magnetic-field TBC kernels may support undesired spurious modes. A combined-field TBC kernel is proposed that does not allow for the buildup of resonant modes. Its functionality is demonstrated by two numerical examples.