A NOVEL SYNTHESIS TECHNIQUE FOR MICROWAVE BANDPASS FILTERS WITH FREQUENCY-DEPENDENT COUPLINGS

This paper presents a novel synthesis technique for microwave bandpass fllters with frequency-dependent couplings. The proposed method is based on the systematic extraction of a dispersive coupling coe-cient using an optimization technique based on the zeros and poles of scattering parameters representing two coupled resonators. The application of this method of synthesis is illustrated using two examples involving four and flve-pole generalized Chebyshev fllters implemented in substrate-integrated waveguide (SIW) technology. As a dispersive inverter, a parallel shorted stub with an additional septum was used. The septum lends greater ∞exibility to the dimensional synthesis, in that it increases the allowable range of the coupling coe-cients. The measured and simulated results are in excellent agreement, which conflrms the validity of the proposed approach.