Highly efficient method to calculate S‐parameters of microwave filter and duplexer from coupling matrix

In this article, a highly efficient approach is presented for obtaining scattering parameters from the coupling matrix of a microwave filter and duplexer whether they are lossless of lossy. By analyzing and making the application of eigenvalue decomposition theory to calculate the inversion of the coupling matrix, a new set of formulas are generated to calculate the scattering parameters. The example of a 14-cavity crossing coupled filter and a 17-order duplexer are calculated and fabricated for illustrating the capabilities of the new proposed approach. Compared with the traditional method in textbook, the time consumed on computing is shortened by 80%, which validates that the method in this article has a huge advantage in handling S-parameter calculation of filter and duplexer with multiple couplings.