Miniaturised dual-band bandpass filter using modified SIR

A novel miniaturised dual-band bandpass filter using a single modified stepped impedance resonator (SIR) is presented. Some different shaped slots cutting on the middle patch of the SIR are adopted to improve the return loss in the two passbands and control the resonant frequencies. Meanwhile, the impedance ratio can be changed by changing L or W to tune the resonant frequencies. To improve the selectivity and achieve a high out-of-band rejection, source-load coupling is utilised. The simulated and measured results are presented and show good agreement.