A Compact Dual-Wideband Bandpass Filter Based on Open-/Short-Circuited Stubs

A dual-wideband bandpass filter is proposed and analyzed, which is based on loaded open-/short-circuited stubs. The dual-band filter consists of a second-order bandpass filter and a third-order bandpass filter, which can be designed separately. The bandwidth of two passbands can be adjusted by tuning the impedance and the length of the stubs. A dual-band bandpass filter prototype operating at 2.4/5.2 GHz is designed for demonstration. It shows a low insertion loss of 0.3 dB and wide bandwidth of 51.9% at 2.4 GHz and 23.3% at 5.2 GHz. The filter structure is simple without narrow coupling gap between resonators, which is easy for fabrication.