Accuracy considerations for FDTD field solutions

The finite difference time domain (FDTD) method of solving electromagnetic problems is gaining popularity. This is due to the simplicity of the technique, and to its ability to solve very complicated problems. Scattering from an infinitely long perfect electrical conductor (PEC) cylinder is studied to show how accuracy varies with field sampling point location. It is shown that accuracy varies with respect to the location of the field sampling point, and convergence at one point does not guarantee that the other points in the problem space have converged. Scattering from a PEC cylinder is also used to show how low frequency field solutions are affected by the number of time steps used in the FDTD algorithm. For low-frequency solutions, the FDTD algorithm has to run long enough to capture the low frequency spectra. Additionally, the absorbing boundaries have to be placed far away enough so that reflections do not contaminate the low frequency spectra of the signal.