Dual-band filter using asymmetrical stub-loaded resonator with independently controllable frequencies and bandwidths

A new kind of asymmetrical stub-loaded resonator is proposed and applied to design a dual-band bandpass filter (BPF) with independently controllable frequencies and bandwidths. The asymmetrical stub-loaded resonator presented in this study has more superior performance than the conventional symmetrical stub-loaded resonator. By appropriately selecting the lengths of the loaded stubs of the resonator, the first two resonant frequencies can be tuned independently without having influence on each other. The bandwidth of each passband of the proposed dual-band filter using asymmetrical stub-loaded resonators can be controlled independently by adjusting the coupling parameters. To validate the concept, one microstrip dual-band BPF centred at 2.4 GHz/5.2 GHz is designed, fabricated and measured. It is found that the simulated and measured results are in good agreement.