Compact dual-band BPF with SR and SMR for wideband and WLAN applications
A compact dual-band bandpass filter (BPF) with a slotline resonator (SR) and a short stub centre-loaded microstrip resonator (SMR) is proposed for wideband and wireless local area network (WLAN) applications. The high-impedance microstrip feedlines for the filter with the SMR can function as the quarter-wavelength resonators for the filter with the SR to realise a wideband passband. Owing to the source–load coupling, the loaded short stub and the intrinsic characteristics of the SMR, three transmission zeros can be created to improve selectivity and isolation. Compact size can be obtained by adopting the folded SR and folded SMR inserted between the arms of the SR. A compact dual-band BPF for wideband and WLAN applications is simulated and measured, and good agreement can be obtained between the measured and simulated results.