Improved diagnosis of lossy resonator bandpass filters using Y-parameters

This article presents a generalized coupling matrix (CM) extraction technique directly from the measured or electromagnetic simulated admittance parameter (Y-parameters) of a narrow band cross-coupled resonator bandpass filter with losses. The characteristic polynomials corresponding to the Y-parameters rather than the S-parameters are derived and then determined by the Cauchy method. Once determining the characteristic polynomials, the complex poles and residues of Y-parameters are also determined. Using these complex poles and residues, the complex CM can be obtained by a sequence of similarity transformations, and then the desired extracted CM and unloaded Q for each resonator are obtained from this complex CM. To verify the effectiveness of the proposed method, three filter CM extraction examples are demonstrated. (c) 2015 Wiley Periodicals, Inc.