Validation of Frequency-Dependent Transmission Line Models

The accuracy of a transmission line model can be verified by comparing its response to that by an alternative method of indisputable accuracy. This paper shows a procedure for validation which is based on the inverse Fourier transform. Desired test responses are calculated in the frequency domain using an admittance representation of the line and its terminal conditions. Time-domain step responses are calculated using the inverse Fourier transform, with semianalytic integration between sample points to permit calculation at arbitrarily large time values. The required number of frequency samples is greatly reduced by adaptively calculating the samples while considering the frequency-domain behavior of the integrand. Responses from arbitrary excitations are calculated by superposition of weighted, time-delayed step responses. The accuracy of the approach is validated for an overhead line and a cable system by comparison with responses obtained by a phase-domain line model.