Circuit Model Extraction of Coupled-Resonator Filters and Multiplexers Via Direct Use of S-parameter AAA Fitting

A new method is proposed for coupling matrix extraction for coupled-resonator filters and multiplexers, which directly transforms measured S-parameters to the transversal coupling matrix via the adaptive Antoulas-Anderson (AAA) barycentric rational fitting technique. This method is not dependent on the numerical algorithm that transforms S-parameters to Y-parameters and can be used to overcome the challenge of obfuscated poles in Y-parameter frequency responses.