Compact microstrip dual-mode dual-wideband bandpass filter for GPS/WiMAX application

This paper presents a novel dual-mode dual-wideband bandpass filter (BPF) structure. The proposed structure exhibits two resonant modes in each passband and two transmission zeros located at the lower side of the first passband and the upper side of the second passband. There is a transmission zero between two passbands, which can improve the band-to-band isolation. As an example, a dual-mode dual-wideband BPF centered at 1.59/3.51 GHz with 3 dB fractional bandwidth of 32%/16% is designed and fabricated. The fabricated filter has the compact size of 0.07λ_g × 0.17λ_g. Good agreement can be observed between the simulation and the measurement.