FD-TD analysis of electromagnetic wave radiation pattern of aperture and horn antennas

The authors describe the numerical error caused by the finite mesh size of the FD-TD (finite-difference time-domain) algorithm in far-field radiation pattern study. It is demonstrated that numerical dispersion of the FD-TD method causes the overall shape of the radiation pattern to be shifted to the diagonal direction of the FD-TD mesh. In the numerical simulation of the aperture and horn antenna, the amount of this shift can be predicted, and it has been confirmed by the numerical results. Based on a comparison between the theoretical and predicted results, a simple algorithm was developed to improve the accuracy of the numerical results. The algorithm described should be useful for applications of the FD-TD method to wave propagation problems.<>