A novel high selectivity dual-band band-pass filter with inductive source-load coupling

A novel high selectivity dual-band band-pass filter (BPF) is presented in this article. This BPF incorporates two sets of resonators: two one-wavelength microstrip line resonators with one end short-circuited on the top layer for generating the second passband and a dual-mode defected ground structure resonator (DDGSR) on the bottom layer for generating the first passband. The two microstrip line resonators are used not only as resonant elements, but also as a part of the feed structures with inductive source-load coupling for exciting the DDGSR. Using the intrinsic characteristics of the resonators and feed structures, multiple transmission zeros located at both sides of the first passband can be realized to achieve high selectivity. An experimental dual-band BPF located at 2.4/4 GHz has been simulated and fabricated. This design method is verified by good agreement between the simulated and measured results.