Transmission-line matrix analysis of continuous waveguiding structures using stepped-impedance cavities

Up to the present time, the t.l.m. method of numerical analysis has found the dispersion characteristics of continuous waveguiding structures by obtaining the resonant frequencies of quarter wavelength cavities. Long cavities requring many nodes have been necessary, and the computer power required for solution becomes excessive as the frequency of interest decreases. This paper shows how cavities of any length may be represented by stepped impedance cavities which, for the t.l.m. method, are only two mesh lengths long for 2-dimensional analysis and 2.5 mesh lengths long for 3-dimensional analysis. The savings in computer time and storage, using the stepped impedance technique, may be of the order of 100 times.