Bandwidth tuning of resonator filter using reduced number of tunable coupling structures

Boyoung Lee, Seunggoo Nam, Juseop Lee

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


This paper presents a new bandwidth tuning theory for Butterworth-response resonator filters. The presented theory shows that the bandwidth of odd-order Butterworth filters can be varied by adjusting only two interresonator coupling structures while maintaining a perfect impedance matching at the center frequency. In other words, this paper presents an analytic approach to reduce the number of tunable coupling structures when designing a bandwidth-tunable resonator filter. Theories for third- A nd fifth-order direct-coupled filters are discussed in detail, and it is shown that only two interresonator coupling structures are required to be tunable. In addition, for verifying the new bandwidth tuning method, a fifth-order cylindrical cavity filter has been designed, fabricated, and measured. The fabricated filter has an 11:1 bandwidth tuning range.

Original languageEnglish
Article number8653495
Pages (from-to)1496-1503
Number of pages8
JournalIEEE Transactions on Microwave Theory and Techniques
Issue number4
Publication statusPublished - 2019 Apr

Bibliographical note

Funding Information:
Manuscript received August 18, 2018; revised December 11, 2018; accepted January 2, 2019. Date of publication February 26, 2019; date of current version April 3, 2019. This work was supported by the Korea Government (Ministry of Science and ICT) through the National Research Foundation of Korea under Grant NRF-2018R1A2B6006095. (Corresponding author: Juseop Lee.) The authors are with the College of Informatics, Korea University, Seoul 02841, South Korea (e-mail:

Publisher Copyright:
© 2019 IEEE.


  • Bandwidth tuning
  • cavity resonator
  • interresonator coupling
  • topology

ASJC Scopus subject areas

  • Radiation
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


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