Synthesis of Resonators for BPF with Quarter-Wave Couplings and Wide Rejection Band

The problem of synthesis of stepped-impedance resonators (SIR) for bandpass filters (BPF) with quarter-wave couplings and wide rejection band is solved. The synthesis is based on a new approach, which consists in simultaneous use in BPF of quarter-wave resonators and SIRs, in which the location of critical frequencies (resonant and antiresonant) is of mutually opposite nature. General relationships for determining the parameters of such resonators are established. Characteristic impedances of the synthesized SIRs are systematized in the form of a table. For the synthesis of SIRs, general formulas were established, which significantly simplify the process of calculating characteristic impedances for a given function of the input impedance of the resonator. The rejection band in BPFs with synthesized SIRs can be a decade or more.