On a method to obtain z-domain functions of wave digital network for elliptic lowpass microstrip filter

An analysis method is presented for evaluating the z-domain scattering parameters of wave digital network (WDN). WDN represents a model of microstrip structure based on one-dimensional wave digital approach. It is formed by connecting several multiport networks together. Method is a quite general and can be employed to analyze different microstrip filter circuits. The closed-form solutions to WDN can be derived which enables to characterize in the shortest possible time the microstrip structure in the whole frequency range. Both theoretical analysis and experimental results are given, showing good agreement.