Generation of accurate rational models of lossy systems using the Cauchy method

A method to generate an accurate rational model of lossy systems from either measurements or an electromagnetic analysis is presented. The Cauchy method has been used to achieve this goal. This formulation is valid either for lossless or lossy system responses. Thus, it provides an improvement over the conventional Cauchy method and takes into account the relationship between the transmission and reflection coefficients of the system which in our case is a filter. The resulting model can be used to extract the coupling structure of the filter. Two examples have been presented. One deals with measured data and the other one uses numerical simulation data from an electromagnetic analysis.