Design of dual-band bandpass filter using asymmetrical stub-loaded resonators

A novel structure for designing a dual-band bandpass filter(BPF) using asymmetrical stub-loaded resonators(SLRs) with independently controllable center frequencies and bandwidth is presented in this paper. By appropriately selecting the length of the SLR, the harmonic frequencies can be tuned for generating the dual-passband response. Using this structure to the filter, the bandwidth of each passband can be controlled independently by adjusting the coupling spacing. The new structure can generate two transmission zeros in the insertion loss response. To validate the design, a dual-band BPF centered at 3.5-GHz/5.2-GHz were fabricated and measured. It is shown that the measured and simulated performance are in good agreement.