Synthesis of ultrawideband bandpass filter by multisection of commensurate stepped-impedance resonators

A novel filter prototype composed of multiselection of stepped impedance resonators (SIRs) is proposed to realize the wideband bandpass (UWB) filter. The relation between the modes number and stage number of resonators is first discussed, followed by the derivation of the corresponding Chebyshev filtering Junction. Furthermore, the equivalent circuit model of this new filter prototype is established based on the transmission-line theory for filter synthesis. As air example, a FCC UWB filter is synthesized with the proposed filter Prototype to possess a passband from 3.1 to 10.6 GHz (fractional band-width is about 110%). The synthesized circuit model are further optimized by EM simulator, fabricated in microstrip line. cold characterized by network analyzer. The good agreement between the measured and predicted frequency responses validates the effectiveness of newly proposed synthesis approach. In addition, the designed filter exhibits good characteristics of comparatively low insertion loss, quite sharp skirts. very flat group delay, and good stopband (especially in lower one) as well. (C) 2008 Wiley Periodicals, Inc.