Compact triple band bandpass filters design using mixed coupled resonators

In this paper a study on designing Triple Band (TB) Bandpass Filter (BPF) by exploiting Triple Mode Resonator (TMR) is presented. By connecting stepped impedance and radial stubs in a categorical manner, a TMR can be obtained which is the basic component for designing this TB BPF. Microstrip lines are tapped over the resonator to work as feed lines and also to generate transmission zeros. The TMRs are Mixed Electric and Magnetic Coupled (MEMC) which help in generating additional Transmission Zeros (TZs) around passbands. As verification, a TB BPF is designed, fabricated and measured. In the designing process, first, a Dual Band (DB) BPF is designed and analyzed completely with the help of even-odd mode analysis. Extraction of lumped component model for the DB BPF is done in order to study the circuit model of the filter. Then the work is extended to design a Triple Band-Band Pass Filter. The fabricated filters offer an advantage in terms of compact size, low insertion loss, good inter band isolation and harmonic suppression. (C) 2019 Elsevier GmbH. All rights reserved.