A coupled line bandpass filter using a novel SIR with intentional coupled length

ABSTRACT A novel stepped impedance resonator (SIR) and its design formulas for the coupled line bandpass filter (BPF) are proposed. The proposed SIR can provide tight coupling by intentionally extending the length of a coupled line. In addition, it forms the second passband much farther away compared to the conventional SIR. To show the validity of the proposed SIR and its application to the coupled line BPF, the three‐pole SIR BPF is designed and fabricated. The measured and simulated results are in very good agreement. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1259–1262, 2015