Efficient FDTD S-parameter calculation of microwave structures with TEM ports

We have presented an accurate and efficient method for S-parameter calculation. The method uses a variation on the total field-scattered field formalism, the modes are injected and extracted at the interface between the total field and the error field regions. As such the propagated energy never actually reaches the boundary conditions, so these conditions can be less stringent, and should require less resources. Furthermore, the mode distributions are used to excite the structure and to calculate the amplitude of the propagating mode. This allows us to place both the excitation mechanism and the port regions very close to the simulated structure, again saving resources, as well as preserving the accuracy of the method. However, due to the dispersion of non-TEM modes, this method can only be used if the mode of interest is TEM. Our method has been compared with the method of moments approach and the results are almost identical.