Dual-band bandpass filter with controllable center frequency and bandwidth using short stub-loaded SIR and tri-section SIR

A novel compact dual-band bandpass filter (BPF) based on short stub-loaded stepped impedance resonator (SSL-SIR) and a pair of tri-section stepped impedance resonator (T-SIR) is presented. The dual-band BPF can be divided into two sub filters. The upper sub filter creates the first passband centered at 2.4 GHz, and the lower sub filter generates the second passband centered at 3.5 GHz. The two passbands can be controlled separately and have almost no mutual influence between each other. The structure of the filter is miniaturized and a wide stopband performance is also achieved by introducing SIR. The simulated and measured results are both presented and show good agreement.