Accurate plane-wave excitation in the FDTD method

Several different techniques have previously been developed to implement plane-wave excitation in the finite-difference time-domain (FDTD) method, such as the initial-condition technique, the hard-source technique, and the connecting-condition technique used in the total-field/scattered-field (TF/SF) formulation. In the TF/SF formulation, the incident field has to be computed and "fed" to the three-dimensional (3D) FDTD grid on the boundary separating the total-field and the scattered-field regions. Since the incident field is a known quantity, a closed-form expression can be evaluated on every point of this boundary at each time step. However, a more efficient way of computing the incident field is to use an incident-field array (IFA), which is a one-dimensional (1D) FDTD grid set up to numerically propagate the incident field into the 3D FDTD grid. Then, the required incident-field values on the TF/SF boundary are interpolated from the values on the IFA. Here, several signal-engineering techniques are outlined that can be employed to enhance the accuracy of the plane-wave excitation in the finite-difference time-domain (FDTD) method.