Compact and high selectivity dual-band dual-mode microstrip BPF with folded SIR

In this paper, a compact and high selectivity dualband dual-mode microstrip bandpass filter (BPF) with source-load coupling is proposed using the short-stub-loaded folded SIR. Five transmission zeros can be generated near the passband edges and in the upper-stopband to improve the frequency selectivity and stopband performance, due to the main path signal counteraction and the folded arms of the resonator. The locations of the transmission zeros and stopband rejection level can be adjusted simply by varying the source-load coupling structure. Finally, a dual-band dual-mode BPF for GPS and WLAN applications is designed, fabricated and measured for experimental verification of the predicted results. And the measured results agree well with the EM simulations.