BalancedUltra-WidebandBPFDesignUsingSlotlineResonator.docVIP

PAGE  PAGE 4 Balanced Ultra-Wideband BPF Design Using Slotline Resonator Chung-Jung Chen#1, Ching-Her Lee #2, Chung-I G. Hsu *3, and Jhih-Hong Chang #4 # Graduate Institute of Communications EngineeringNational Changhua University of Education, Changhua 500, Taiwan1 .tw 2iecher@cc. .tw4 HYPERLINK mailto:m9957005@.tw m9957005@.tw* Department of Electrical EngineeringNational Yunlin University of Science and Technology, Yunlin 640, Taiwan3cghsu@.tw Abstract—This paper presents a new balanced ultra-wideband (UWB) bandpass filter (BPF), which is designed using a slotline multi-mode resonator (SLMMR). The SLMMR and the orthogonally crossed microstrip feed-lines extend beyond the microstrip-slotline junction by a quarter-wavelength around the passband center frequency of the BPF to ensure good differential-mode (DM) signal transmission. On the other hand, the SLMMR is deployed such that the quarter-wavelength resonances occurring near the input and output sides of the resonator are well decoupled so as to enhance the common-mode (CM) signal rejection. The measured minimum DM insertion loss is 0.92 dB in the DM passband, in which the measured CM suppression is larger than 17.1 dB. Index Terms —Balanced bandpass filter, UWB system, differential-mode operation, common-mode suppression I. Introduction In recent years, the research interest of ultra-wideband (UWB) devices has been aroused in both the academic and industrial areas [1-5] since the U. S. FCC (Federal Communications Commission) approved the unlicensed use of frequency spectrum from 3.1 to 10.6 GHz. Filters which meet the required UWB specification have also been developed and extensively investigated based on various methodologies proposed in the literature [1, 6, 7]. Most of the UWB bandpass filters (BPFs) available in published papers are those of single-ended ones. However, since balanced circuit structures are widely used in modern communication systems due to their good signal-no