Dangling Circuit Extraction for Coupled-Resonator Diplexers and Multiplexers

This article first introduces a simple analytical element extraction approach for two-port coupled-resonator networks with dangling resonators. The proposed extraction method offers an analytical procedure to extract elements step-by-step from admittance matrix polynomials, along with discussions on the rules for the extraction of couplings, resonator junctions, and dangling resonators. Furthermore, by extending the dangling resonator concept to a "dangling circuit", a novel circuit model extraction method for coupled-resonator multiplexers is developed. Within an individual extraction process, all circuits are reduced to a two-port network. The channel of interest is focused exclusively while all other channels are dangling branch circuits. The proposed method can be recursively implemented, making it applicable to coupled-resonator multiplexers with multiple resonator junctions. To demonstrate the capabilities of the proposed approach, a circuit model extraction example for a fabricated diplexer and a circuit model extraction example for an electromagnetic (EM) simulated triplexer are presented, respectively.