Finite-difference time-domain solution of electromagnetic scattering problems

The "finite-difference time-domain" (FDTD) method is an efficient and powerful way to solve three-dimensional scattering problems. Unbounded medium problems are easily solved in this method using the absorbing boundaries, but the FDTD method is especially efficient for problems involving inhomogeneous media, since the number of unknowns remains the same when the scatterer is changed in the same geometry of the computational domain. Perfectly matched layers (PML) can be incorporated to match nonhomogeneous media, which helps the FDTD to solve the scattering from special geometries such as buried scatterers. The total-field formulation can be used to simulate the propagation of the incident waves into the computational region. The far-zone transformation technique enables us to compute field parameters far from the scatterer using near-field scattering information. However, there are errors in the plane-wave generations in the FDTD method. These errors are observed in both the near-field and the far-field variables. The major sources of these errors are the high-frequency components in the input signal and the numerical dispersion. These errors can be significantly reduced by using special techniques.