Efficient Determination of Reverberation Chamber Time Constant

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Determination of the rate of energy loss in a reverberation chamber is fundamental to many different measurements such as absorption cross-section, antenna efficiency, radiated power, and shielding effectiveness. Determination of
the energy decay time-constant in the time-domain by linear fitting the power delay profile, rather than using the frequency-domain quality factor, has the advantage of being independent of the radiation efficiency of antennas used in the measurement. However, determination of chamber time constant by linear
regression suffers from several practical problems, including a requirement for long measurement times. Here we present a new nonlinear curve fitting technique that can extract the time-constant with typically 60% fewer samples of the chamber transfer function for the same measurement uncertainty, which enables faster measurement of chamber time constant by sampling fewer chamber transfer function, and allows for more robust automated data post-processing. Nonlinear curve fitting could have economic benefits for test-houses, and also enables accurate broadband measurements on humans in about ten minutes for microwave exposure and medical applications. The accuracy of the nonlinear method is demonstrated by measuring the absorption cross-section of several test objects of known properties. The measurement uncertainty of the method is verified using Monte Carlo methods.
Original languageEnglish
Pages (from-to)1296-1303
JournalIEEE Transactions on Electromagnetic Compatibility
Issue number5
Early online date14 Dec 2017
Publication statusPublished - Oct 2018

Bibliographical note

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Submitted 1 August 2017, Accepted 2 Nov 2017, Online 14 Dec 2017


  • Antenna measurements
  • Frequency measurement
  • Loss measurement
  • Measurement uncertainty
  • Signal to noise ratio
  • Time measurement
  • Absorption cross section (ACS)
  • Monte Carlo method
  • chamber time constant
  • inverse Fourier transform
  • power balance method
  • power delay profile (PDP)
  • reverberation chamber (RC)

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