Design of Capacitively Loaded Coupled-Line Bandpass Filters with Compact Size and Spurious Suppression

Marco Orellana, Jordi Selga, Paris Velez, Marc Sans, Ana Rodriguez, Jordi Bonache, Vicente E. Boria, Ferran Martin

Research output: Contribution to journalArticleResearchpeer-review

24 Citations (Scopus)

Abstract

© 1963-2012 IEEE. This paper is focused on the synthesis of capacitively loaded coupled lines for the design of bandpass filters with compact size and spurious suppression. The filters consist of cascaded pairs of coupled lines periodically loaded with patch capacitors. The loading capacitances provide a slow-wave effect to the coupled lines useful for filter miniaturization, whereas periodicity introduces bandgaps that can be controlled in order to achieve spurious suppression. Filter design is achieved following an automated process based on aggressive space mapping (ASM) optimization. The two reported examples, a third-order filter with central frequency f-{0} = 1.0 GHz, 8% fractional bandwidth, and 0.1-dB ripple level and a fifth-order filter with central frequency f-{0} = 1.8 GHz, 8% fractional bandwidth, and 0.1-dB ripple level, demonstrate the potential of the proposed ASM-based design approach, as well as the effectiveness of the loading capacitances to reduce filter size and reject the spurious bands. Significant size reduction in both filters is achieved, whereas the out-of-band rejection is better than 30 and 45 dB in the third-order and fifth-order filters, respectively, up to at least 4f-{0}.
Original languageEnglish
Article number7807287
Pages (from-to)1235-1248
JournalIEEE Transactions on Microwave Theory and Techniques
Volume65
Issue number4
DOIs
Publication statusPublished - 1 Apr 2017

Keywords

  • Bandpass filters
  • circuit synthesis
  • coupled lines
  • electromagnetic bandgap
  • microstrip technology
  • slow-wave transmission lines
  • space mapping

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