Compact elliptic-function coplanar waveguide low-pass filters using backside metallic patterns

Miguel Durán-Sindreu, Jordi Bonache, Ferran Martín

Research output: Contribution to journalArticleResearchpeer-review

18 Citations (Scopus)


In this letter, compact elliptic-function low-pass filters (LPF) implemented in coplanar waveguide technology by etching stepped impedance resonators (SIR) in the back substrate side, are presented. The required transmission zeros of the elliptic-function response are provided by the shunt connected SIRs. As an illustrative example, an order-3 prototype LPF with 1 GHz cutoff frequency is designed and fabricated. The measured stop-band rejection is better than 30 dB up to 6.4 GHz, and a narrow transition band is obtained. To demonstrate the possibilities of the approach to synthesize arbitrary elliptic-function responses and order, a fifth-order elliptic LPF with 1 GHz cut-off frequency is also designed and fabricated. Filter dimensions are as small as 6.6 mm × 9.2 mm, i.e, 0.034λ × 0.047λ, for the third-order filter, and 12.1 mm × 13 mm (0.062λ × 0.067 λ) for the fifth-order filter, λ being the guided wavelength at cutoff. © 2010 IEEE.
Original languageEnglish
Article number5565378
Pages (from-to)601-603
JournalIEEE Microwave and Wireless Components Letters
Publication statusPublished - 1 Nov 2010


  • Coplanar waveguide (CPW)
  • elliptic-function filter
  • low-pass filter (LPF)
  • stepped impedance resonator (SIR)


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