Compact Triple-Passband Bandpass Filter Using Asymmetric Stepped Impedance Resonators

This letter proposes the triple-passband bandpass filter based on stepped impedance resonators (SIRs) and asymmetric stepped impedance resonators (ASIRs). The filter has the advantages of compact circuit size, high passband selectivity, and low insertion loss. Furthermore, the asymmetric stepped impedance resonators are designed appropriately to make transmission zeros. This bandpass filter has three passbands at 2.4 GHz, 5.2 GHz, and 5.9 GHz. Therefore, the resonant frequencies and transmission zero can be easily controlled by controlling the impedance and length ratios of stepped impedance resonators (SIRs) and asymmetric stepped impedance resonators. As a result, the proposed filter has the advantages of low loss, compact size, and uncomplicated design rules for applying to multi-band and multi-service wireless communication systems.