Analysis and Synthesis of Coupled Microstrip Circuits with More Than Two Coupled Strips

It is shown that the y-parameters for the 2N-port network, N coupled strips form, may be found using almost arbitrary quasi-propagation modes if the relative bandwith of interest is small. Chosing a special set of propagation modes leads to simple expressions for the y-parameters, which are easy to use in an iterative synthesis procedure. The use of quasi-modes also facilitates the calculation of primary parameters (capacitances and phasevelocities). A further advantage is that empirical formulas may be used. Such formulas were developed, which give surprisingly accurate results.