Miniaturized quad-band bandpass filter using quad-mode stepped impedance resonator

ABSTRACTA miniaturized quad-band bandpass filter (BPF) using compact quad-mode stepped impedance resonator (IQMSIR) is proposed. Based on the symmetric presented by the resonator, four modes are deduced using even-and odd-mode technique. Design formulas are also derived and they are used to guide the filter design. Multiple coupling circuit technique is employed to realize the four passbands. Independent design for four passbands are achieved due to the physical dimensions and additional cross slots. Upper stopband is performed by adding open loop SIR at I/O ports. Transmission zeros among each passbands are generated, resulting in high isolation and selectivity. A quad-band filter is designed, fabricated and measured. The operating central frequencies of the fabricated filter are at 2.54/3.36/5.24/6.6 GHz. The measured 3-dB fractional bandwidths of the four passbands are about 3.9/6.4/4/4.6% and the minimum insertion losses are about 2.3/0.89/3.2/2.3 dB. Measurements correlate well with the simulation results.KEYWORDS: Miniaturized bandpass filterquad-bandquad-mode stepped impedance resonatorcross couplingtransmission zero (TZ) Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThis work was supported in part by the National Natural Science Foundation of China [Grant Number 62171097] and by the National Defense Basic Scientific Research program of China [Grant Number JCKYS2021DC07].Notes on contributorsShichao JinShichao Jin received the B.S. degree in physics from Lanzhou University, Lanzhou, China, in 2004, and the Ph.D. degree in physics from Tsinghua University, Beijing, China, in 2009. He was a senior RF&SatCom engineer from 2009 to 2017 and a professor from 2017 to 2020 with the Beijing Institute of satellite Information Engineering, Beijing, China. He is currently with State Key Laboratory of Space-Ground Integrated Information Technology. He has 13 years' experience in communication systems, microwave circuits, active phased array antenna. His current research interests include satellite communication systems, synthetic aperture radar, RF/analog and millimeter-wave integrated circuits and systems.Kaijun SongKaijun Song (M'09-SM'12) received the M.S. degree in radio physics and the Ph.D. degree in electromagnetic field and microwave technology from the University of Electronic Science and Technology of China (UESTC), Chengdu, China, in 2005 and 2007, respectively. Since 2007, he has been with the EHF Key Laboratory of Science, School of Electronic Engineering, UESTC, where he was a Full Professor. From 2007 to 2008, he was a Postdoctoral Research Fellow with the Montana Tech, University of Mon[1]tana, Butte, MT, USA, working on microwave/millimeter-wave circuits and microwave remote sensing technologies. From 2008 to 2010, he was a Research Fellow with the State Key Laboratory of Millimeter Waves of China, Department of Electronic Engineering, City University of Hong Kong, on microwave/millimeter-wave power-combining technology and Ultra-Wideband (UWB) circuits. Since 2018, he has also been a Full Professor with the School of Electronic Science and Engineering, UESTC.Xueyuan DingXueyuan Ding began his studies at UST in 2017, received his undergraduate degree in 2021. Currently, he is pursuing a master's degree at the University of Electronic Science and Technology.