Design of compact triple-passband bandpass filter

The compact triple-passband bandpass filter base on uniform impedance ring resonators (UIRRs) is proposed. The filter has advantages of high passband selectivity, having closed adjacent passbands and compact circuit size. The resonators with magnetically coupling by grounding via hole are designed to have tree resonant paths at 1.22 GHz, 1.5 GHz and 1.8 GHz. The resonant frequencies can be easily controlled by tuning L3, L4 and L5 for each resonant paths of the resonator. The triple-passband bandpass filter is showing a simple configuration, an effective design method and a small circuit size. The measured results are in good agreement with the simulation results.