Direct-Coupled-Resonators Bandpass Filters with Arbitral End-Coupled-Series-Immittances

M. Zaradny (Wrocław Univ. of Science and Techn., Poland)

This paper presents novel analytical method of synthesis for BPF’s with consideration of arbitrarily series immittance-parts entered between resonators and to the real terminations. Filters with coupled-immittances provide higher degree of freedom in designing – arbitral filter image impedance, slopes of resonators, or adjusting of responses out of the pass-band. Cohn and others have not noticed in their papers that the problem is invertible in slightly different way in networks by Cohn revised, and until today, none of the authors have presented this transformation novel-approach with closed-form of analytical synthesis. Presented method gives an opportunity to apply arbitrarily coupled-immittances and any immittances of intermediate resonators in ladder network. In this paper authors have compared the old-theory approach with non-inertive inverters to novel approach. Analytical calculations and numerical S-parameter graphs have been shown as examples of synthesized-data filters elements. Moreover, several filters with 30% of FBW were designed.