Novel T-Shaped Non-orthogonal Dual-Mode Band-Pass Filters with Two Differently Structured Resonators
Novel dual-mode filters with two differently structured resonators were designed on Al2O3 ceramic substrates to achieve pattern minimization and better filter properties. The input/output microstrip lines were arranged in a straight line, making the desig
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Abstract Novel dual-mode filters with two differently structured resonators were designed on Al2O3 ceramic substrates to achieve pattern minimization and better filter properties. The input/output microstrip lines were arranged in a straight line, making the designed filter easy to connect with other RF circuits. To promote a coupling effect between the input/output microstrip lines and the resonator, two additional coupling stubs were used to form modified T-shaped microstrip coupling lines. In a dual-mode filter, adding a perturbation stub could generate two degenerate modes and increased the bandwidth in the desired passband. To achieve this, the type-A dual-mode filter was designed on a square-ring resonator with two perturbation stubs. For the type-B filter, two open stubs, one perturbation patch, and one meandering loop ring resonator were investigated to achieve the same purpose but with a smaller pattern size than type-A. According to simulated results, the proposed filters with optimized parameters exhibited the wide passbands. Keywords Phase difference • Al2O3 • Asymmetric bandwidth • Dual band
C.Y. Kung • C.F. Yang (*) Department of Chemical and Materials Engineering, National University of Kaohsiung, Kaohsiung, Taiwan, R.O.C. e-mail: [email protected] Y.T. Hsieh • W.C. Chang Department of Electronic Engineering, Southern Taiwan University, Tainan, Taiwan, R.O.C. C.G. Kuo Department of Industrial Education, National Taiwan Normal University, Taipei, Taiwan, R.O.C. C.C. Diao Department of Electronic Engineering, Kao Yuan University, Kaohsiung, Taiwan, R.O.C. J. Juang and Y.-C. Huang (eds.), Intelligent Technologies and Engineering Systems, Lecture Notes in Electrical Engineering 234, DOI 10.1007/978-1-4614-6747-2_78, # Springer Science+Business Media New York 2013
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1 Introduction Microstrip planar filters have garnered increased attention in recent years for their use in modern wireless communication networks [1, 2]. Compact size, wide bandwidth, small insertion loss, and high out-of-band rejection are requisite properties, and because dual-mode filters meet these demands, they have attracted interest in the investigation of band-pass filters (BPFs) [3, 4]. Each resonator of a dual-mode filter is regarded as a doubly tuned resonant circuit, so the required number of resonators can be cut in half [5]. Filters with ring-type dual-mode resonators are more compact than filters with patch-type dual-mode resonators, and they meet commercial requirements; various dual-mode microstrip line filters have been proposed in theory and experimentally, such as circular ring [6, 7] and square ring [5], triangular ring [8], and hexagonal ring [9]. To create a band-pass filter, the two degenerate modes of a dual-mode resonator are excited and coupled to each other by orthogonal feed lines and a variety of perturbations are added. There are many methods of creating perturbations, such as adding or subtracting a patch on the symmetrical line or on each side [10–12]. However, most dual-mode filte
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