n-path transmission-line theory applied to the analysis of coupled comblines

The first part of this paper considers the generalisations of transfer and image parameters from a 2-port filter section to a 2n-port filter. This latter system is found to have n modes of operation. These are derived together with a terminating impedance matrix. This matrix represents a network of elements which, if physically realisable, will terminate all the modes of the system. From a knowledge of the eigenmodes the mode impedance on each line of the filter is derived. In the second part this theory is applied to the analysis of a pair of coupled comblines. The dispersion curves together with those of mode impedance as a function of frequency are plotted. Results obtained are in good agreement with recent experimental results.