Millimeter-Wave Ultra-Wideband Bandpass Filter Employing Dual-Mode Ring Resonators Fed by Step-Impedance Coupled Lines
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Millimeter-Wave Ultra-Wideband Bandpass Filter Employing Dual-Mode Ring Resonators Fed by Step-Impedance Coupled Lines Peng Cai & Zhewang Ma & Hitoshi Kanzaki & Yong Zhang & Bin Chen Received: 23 June 2008 / Accepted: 19 January 2009 / Published online: 19 February 2009 # Springer Science + Business Media, LLC 2009
Abstract This paper presents a novel millimeter-wave ultra-wideband (UWB) bandpass filter (BPF) based on microstrip dual-mode rectangular ring resonators. In order to get strong coupling between the input/output line and the dual-mode ring resonators, a stepimpedance parallel-coupled structure is adopted for the design of the filter. On the other hand, transmission zeros are produced by the dual-mode resonator. As a consequence, the filter has low insertion-loss in its passband, sharp attenuation in its lower and upper stopbands and very wide stopbands. As an example, a filter with two dual-mode ring resonators is designed and fabricated. The measured frequency property of the fabricated filter shows good agreement with the simulated response. Keywords Ultra-wideband (UWB) . Millimeter-wave . Bandpass filter (BPF) . Microstrip dual-mode rectangular ring resonators . Step-impedance parallel-coupled structure
1 Introduction In February 2002, frequency bands 3.1–10.6 GHz and 22–29 GHz were released for commercial communications and automotive radar systems by the Federal Communications Commission (FCC) of the United States [1]. As a key component of these UWB systems, high-performace UWB bandpass filters having low insertion loss, flat group delay in the passband, sharp attenuation in the outband and wide stopbands, are required to control the spectrum of UWB signals. To meet these requirements, many novel UWB filters are reported including microstrip filters using cascaded short-circuited or open-circuited stubs [2], filters developed with dual-mode triangular patch resonators [3], filters based on P. Cai (*) : Y. Zhang : B. Chen School of Electronic Science, Jiangxi University of Finance and Economics, 632 West Feng Lin Street, Nanchang 330013, P.R.China e-mail: [email protected] Z. Ma Department of Electrical and Electronic Systems, Saitama University, Saitama 338-8570, Japan H. Kanzaki Nippon Pillar Packing Co., Ltd., Sanda City, Hyougo 669 - 1333, Japan
J Infrared Milli Terahz Waves (2009) 30:432–438
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multimode resonators [4], filters using cascaded circular ring resonators [5], filters created by the combination of microstrip and CPW structures [6], and filters based on composite lowpass-highpass topology [7]. On the other hand, dual-mode ring resonators with open stubs are very attractive because it can realize transmission zeros in the lower and upper stopbands [8–12]. In [8] and [9], dual-mode square ring resonators loaded with quarter-wavelength open stubs are reported to design UWB filters with fractional bandwidth about 60%. These filters can get sharp attenuations due to the transmission zeros produced by these dual-mode resonators. However, both the lower and upper stopbands of this k
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