Wide-band S-parameter extraction from FD-TD simulations for propagating and evanescent modes in inhomogeneous guides

This paper proposes a new method of S-parameter extraction from finite-difference time-domain simulations. Unlike the previously published methods, the present method extracts the frequency-dependent mode impedance and propagation constant directly from the three-dimensional simulations. This makes it accurate and computationally effective. in wide- band analysis. This paper provides; examples of calculations including difficult cases of inhomogeneous or lossy structures, with the frequency band spanning below, and above the cutoff frequency. Special attention is given to the S-parameter extraction for evanescent modes. It is shown that the available literature provides insufficient and sometimes confusing background in this regard. Thus, a new consistent theoretical background is presented.