Differential-mode wideband bandpass filter for UWB application

The design of a differential-mode wideband bandpass filter (BPF) with good common-mode suppression is presented in this article. The structure of the proposed filter is divided to behave like a bandpass or bandstop filter (BSF) under differential- or common-mode operation. The open stubs in the BSF are used to control the 3-dB bandwidth (BW) of the BPF by slightly reducing the 3-dB cut-off BW of the BSF. To validate the design idea, a differential-mode BPF centered at 4 GHz with a 3-dB BW of 55%, near 30 dB common-mode suppression, is designed and fabricated. (C) 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:197200, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27230