Cold tests and modeling of low-q quasi-optical resonators

Richard P. Fischer, Arne W. Fliflet

Research output: Contribution to journalConference articlepeer-review


Measurements are reported on low-Q open resonators at 85 GHz with a large centered coupling hole in each mirror. This is the first study of open resonators with large diffraction losses and efficient input coupling at millimeter wavelengths. The input resonator for a quasi-optical gyroklystron is described with quality factor Q = 2000 and 13% round-trip losses where approximately 65% of the incident power in the waveguide is coupled to the fundamental TEM00 mode. Two models have been developed to calculate the coupling from the rectangular waveguide through a circular aperture into the open resonator. Both models properly account for the increased diffraction loss of the resonator when coupling apertures are present. Measured results are in reasonably good agreement with values calculated using both scalar diffraction theory and an equivalent-circuit model.

Original languageEnglish (US)
Pages (from-to)59-66
Number of pages8
JournalIEEE Transactions on Microwave Theory and Techniques
Issue number1
StatePublished - 2001
Externally publishedYes
Event2000 Radio-Frequency Integrated Circuits (RFIC) Conference and Automatic Radio Frequency Techniques Group (ARFTG) Meeting - Boston, MA, United States
Duration: Jun 12 2000Jun 16 2000


  • Cold tests
  • Coupling holes
  • Diffraction theory
  • Fabry-perot resonators
  • Millimeter-wave resonators
  • Q factor

ASJC Scopus subject areas

  • Radiation
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


Dive into the research topics of 'Cold tests and modeling of low-q quasi-optical resonators'. Together they form a unique fingerprint.

Cite this