Parameter extraction and correction for transmission lines and discontinuities using the finite-difference time-domain method

The finite-difference time-domain (FDTD) method is useful for performing broadband characterization of uniform transmission lines and discontinuities. Modeling a geometry often requires the implementation of an absorbing boundary condition (ABC). When this is the case, numerical reflections from the ABC´s will add significant error to the calculated transmission line or scattering (S) parameters. This paper introduces a simple post-processing algorithm for extracting these parameters and correcting for numerical reflection error. Furthermore, this method is shown to have a unique relationship to Prony´s method. Practical application and limitations of this technique are also discussed. Finally, the impedance and propagation constant of a microstrip line are calculated using this method