The electromagnetic characteristics of a transparent source for the finite‐difference time‐domain (FDTD) method are investigated. The approximate formulations for the corresponding electric and magnetic fields at the source are first reported, while the associated charges and current are also demonstrated. The approximate E field and H field are very closely related to the FDTD simulated results. It is shown that the magnetic field is proportional to the temporal derivative of the electric field at the source node, while the electric field is proportional to the temporal integration of the driving function. Static charges may be built up to produce static E fields after the driving function has passed, which are responsible for the dc offset problem in the pulsed FDTD algorithm. The dc offset is verified for the case of Gaussian pulse excitation and is avoided via the use of a bipolar pulse.
Journal of the Chinese Institute of Engineers=中國工程學刊 28(5), pp.819-826