A dual-band bandpass filter by interleaving heterogeneous stepped-impedance resonators

A dual-band bandpass filter by interleaving heterogeneous stepped-impedance resonators is presented. Two types of stepped-impedance resonators are designed to have different fundamental resonant frequencies, one for the lower passband and the other for the upper passband. When these two SIRs are properly interleaved, dual passbands can be obtained. This dual-band generation mechanism is distinct from the conventional dual-band generation by using a single type of SIR. A demonstrated circuit was designed at 2.4 GHz and 5.2 GHz. The simulated and measurement results show that the insertion loss less than 1.2 dB and 1.7 dB at operating bands, respectively. Four transmission zeros at 1.8 GHz, 3.8 GHz, 5.8 GHz and 8 GHz are obtained, which significantly improve the stop-band rejection.