Source selection criteria for FDTD models

One of the key components when creating a Finite-Difference Time-Domain (FDTD) model is the method by which the primary source of energy is introduced into the model. Earlier modeling efforts used a variety of primary sources, such as an impressed current source, applied electric field, or a current on a wire. As experience has grown with FDTD modeling, it has been found that because of the very nature of EMI/EMC modeling, the selection of the primary source, or excitation, is significant in ensuring a close resemblance between the numerical model and its physical correspondence. In this paper we examine the different possible excitations and discuss their relevance to modeling, especially in light of the temporal excitation. It is hoped that this work provides insight to the limitations of various sources, and to help the modelers in achieving a stronger correspondence between the numerical simulation and actual physical behavior.