Quasi-TEM approach of coupled-microstrip lines and its application to the analysis of microstrip filters

Authors

  • Fei Xiao,

    Corresponding author
    1. The EHF Key Laboratory of Fundamental Science, School of Electronic Engineering, University of Electronic Science and Technology of China, Chengdu, Sichuan 611731, China
    • The EHF Key Laboratory of Fundamental Science, School of Electronic Engineering, University of Electronic Science and Technology of China, Chengdu, Sichuan 611731, China
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  • Martin Norgren,

    1. Department of Electromagnetic Engineering, School of Electrical Engineering, KTH Royal Institute of Technology, 100 44 Stockholm, Sweden
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  • Sailing He

    1. Department of Electromagnetic Engineering, School of Electrical Engineering, KTH Royal Institute of Technology, 100 44 Stockholm, Sweden
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Abstract

In this article, the quasi-TEM approach is successfully used to analyze coupled-microstrip lines of finite length, which are usually used for the coupling between the source/load and resonators in microstrip filters. First, an orthogonal expansion method is used to extract the per-length inductance and capacitance matrices. The authors then obtain the impedance matrix or admittance matrix, which relates the voltages and currents at both ends of coupled-microstrip lines. To verify our theory, an example is presented, i.e., a Y-shaped dual-mode bandpass microstrip filter, for which, the equivalent circuit model based on the quasi-TEM analysis of coupled-microstrip lines is accurately set up. The approach in this article is applicable to planar microstrip lines with arbitrary number of conductors, under the quasi-TEM assumption. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.

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