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Journal of RF-Engineering and Telecommunications

Editor-in-Chief: Jakoby, Rolf

IMPACT FACTOR 2017: 0.280
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CiteScore 2017: 0.38

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Volume 71, Issue 7-8


Design of Microstrip Lowpass Filter with Sharp Roll-off using Elliptical and Radial Resonators

Gholamreza Karimi / Saeedeh Lotfi / Hesam Siahkamari
  • Young Researchers and Elite Club, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
Published Online: 2016-12-14 | DOI: https://doi.org/10.1515/freq-2016-0111


A new microstrip lowpass filter with sharp roll-off and high suppression level in stop-band is presented. To achieve the lowpass filter with high performance, coupled T-shaped, elliptical and radial resonators are adopted. New formulas for calculating LC equivalent circuit of elliptical and radial resonators are derived based on T-shaped resonators. Transfer functions of the resonators are calculated using the LC equivalent circuits. The designed filter with 3 dB cut-off frequency at 1.67 GHz has been fabricated and measured. Results demonstrate that a relative stop-band bandwidth (RSB) of 157 % (referred to a suppression degree of 30 dB) is obtained while achieving a sharp roll-off about 255.2 dB/GHz. The features of lowpass filter exhibit that the figure of merit is about 45372. Also good agreements are achieved between measured and simulated S-parameters of the fabricated and designed filter.

Keywords: microstrip lowpass filter; LC equivalent circuit; transfer function; elliptical and radial resonators


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About the article

Received: 2016-04-12

Published Online: 2016-12-14

Published in Print: 2017-07-26

Citation Information: Frequenz, Volume 71, Issue 7-8, Pages 349–356, ISSN (Online) 2191-6349, ISSN (Print) 0016-1136, DOI: https://doi.org/10.1515/freq-2016-0111.

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