A Dual-Band Combline Bandpass Filter Loaded by Lumped Series Resonators

This letter presents a dual-band combline bandpass filter (BPF) loaded by lumped series resonators. The proposed filter configuration can easily generate two desired passbands by controlling the resonant frequencies of the comblines as well as the series resonators. Furthermore, the skirt frequency characteristics between the two passbands are improved by transmission zeros introduced by source-load coupling via a lumped element capacitor. Two-pole dual-BPF with center frequencies of 1.2 and 1.54 GHz is designed and the measured results agree well with simulated results.