Compact dual-band BPF for GPS and WLAN with two dual-mode stepped impedance resonators

A compact dual-band microstrip bandpass filter (BPF) is proposed using two dual-mode stepped impedance resonators (SIRs). Either of the dual-mode SIRs can not only separately generate one passband but also control the passband performance. Due to the intrinsic characteristics of the SIRs and source-load coupling, three transmission zeros are created near the passband edges to improve the selectivity of the filter. A dual-band filter located at 1.57 GHz (GPS application) and 2.40 GHz (WLAN application) is simulated and fabricated. Good agreements are obtained between its measured and simulated S-parameters.