Tunable and high directivity coupler for MRI applications

Sung Min Sohn, Anand Gopinath, John Thomas Vaughan

Research output: Chapter in Book/Report/Conference proceedingConference contribution

4 Scopus citations


This paper proposes a tunable and high directivity coupler that is used a RF power monitor in ultra-high field magnetic resonance imaging (MRI) systems. High directivity of a coupler is a critical factor to assure the accurate output in the reflected power measurement. To obtain a tunable and high directivity coupler, a novel directivity tuner includes tunable capacitors and resistors in a passive circuit. A well-tuned capacitance and resistance compensates phase difference and improves directivity in MRI operating frequencies. Therefore, this method significantly reduces the uncertainty of power measurement outputs and can accurately determine reflected power with load variation. The measured results of the proposed coupler agree with the simulation data and achieve excellent isolations (more than 65 dB) and directivities (more than 40 dB) in a compact size of 40 mm × 25 mm.

Original languageEnglish (US)
Title of host publication2014 IEEE MTT-S International Microwave Symposium, IMS 2014
PublisherInstitute of Electrical and Electronics Engineers Inc.
ISBN (Print)9781479938698
StatePublished - Jan 1 2014
Externally publishedYes
Event2014 IEEE MTT-S International Microwave Symposium, IMS 2014 - Tampa, FL, United States
Duration: Jun 1 2014Jun 6 2014

Publication series

NameIEEE MTT-S International Microwave Symposium Digest
ISSN (Print)0149-645X


Other2014 IEEE MTT-S International Microwave Symposium, IMS 2014
Country/TerritoryUnited States
CityTampa, FL


  • Tunable coupler
  • directional coupler
  • high directivity
  • magnetic resonance imaging (MRI)
  • power detection

ASJC Scopus subject areas

  • Radiation
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


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