Design of wide single-/dual-passband microstrip bandpass filters with comb-loaded resonators

Novel microstrip bandpass filters with comb-loaded resonators are proposed. With comb-loaded resonators, the proposed bandpass filter can have a wide passband. In particular, dual passbands show up around 2.45 GHz and 5.75 GHz and their bandwidth is 780 MHz. In addition, by properly controlling passband's coupling coefficient, only one passband of the dual-passband bandpass filter will be generated in the lower/higher frequency band. Finally, the agreement between measured results and the theoretical prediction validates the proposed structure.