Measuring transmission lines parameters in the frequency domain

When a pulse train stimulus is applied to a waveguide or transmission line terminated on an unmatched load, interesting information can be achieved through the analysis of the spectrum of the wave standing along the line. This wave includes both the applied pulse train and the contribution due to the load that reflects part of the incident energy. It can be shown that the profile of the comb-line spectrum characterizing the standing wave is modified as described by a suitable model. The identification of the parameters of the model that fits the measured data, which is performed throughout regression approaches, allows getting information related to line and mismatch parameters.