A COMPACT CPW-FED UWB BPF USING COMBINED MICROSTRIP SIR

This article presents a multimode-resoncaor (MMR)-based ultra-wideband (UWB) bandpass filter (BPF) fed by modified coplanar waveguides (CPWs). The MMR employed in the UWB BPF is formed by combining two quarter-wavelength (lambda/4) microstrip stepped-impedance resonators (SIRs) in a structure-shared fashion. The first two resonant frequencies of the inherent lambda/4 SIRs and the fundamental one of the embedded hay-wavelength (lambda/2) resonator were designed and located inside the UWB passband. Experiments on a prototype UWB BPF were carried out for validating the filter design. The measured frequency responses show an insertion of less than 1 dB between the first and the last vertical bar S-11 vertical bar null frequencies in the UWB passband and an upper -20-dB stopband band-width of about 6.14 GHz. (C) 2009 Wiley periodicals. Inc. Microwave Opt Technol Lett 51: 918-921, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24199