A procedure for computer-aided design of compact diplexers with folded filters

Conventional waveguide diplexers employ in-line cascaded resonators for the realization of the filters, along with T-junction and bends to comply with topological and geometrical constraints. A possible way to reduce the size of the diplexers is to employ bent resonators, so as to combine the topological function of the bend with the filtering properties of the resonators, thus resulting in a folded geometry. A simple but accurate and efficient design procedure of folded diplexer is presented, based on the suhstitutiou of in-line resonators with folded resonators having the same electrical behaviors. The design procedure and optimization are based on a full-wave method employing only the Generalized Scattering Matrix (GSM) of the step discontinuity, thus requiring a reduced computational effort Numerical examples validate the proposed approach.