Dual-band bandpass filters using SIRs with open-stub line and zero-degree feed structure

A novel compact dual-band bandpass filter (DBPF) using SIRs with open-stub line and 0-degree feed structure is presented in this paper. The low-band is obtained by using hairpin type Stepped Impedance Resonators (SIR) split ring through electrical coupling, And by tuning a pair of open-stub lines the high-band is realized too. In order to improve the stop band attenuation, zero-degree feed structure is implemented to introduce three transmission zeros. So the proposed DBPF has high selectivity, and is also simple in design and compact in structure. Finally the proposed filter is designed and fabricated, and the simulation and test results are in good agreement.