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Open AccessArticle

Validation of a Broadband Tissue-Equivalent Liquid for SAR Measurement and Monitoring of Its Dielectric Properties for Use in a Sealed Phantom

1
National Physical Laboratory (NPL), Hampton Road, Teddington TW11 0LW, UK
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ART-Fi SA, 2 Rue Jacques Monod, 91400 Orsay, France
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Laboratoire National de Métrologie et d’Essais (LNE), 29 Avenue Roger Hennequin, 78190 Trappes, France
*
Author to whom correspondence should be addressed.
Sensors 2020, 20(10), 2956; https://doi.org/10.3390/s20102956
Received: 29 April 2020 / Revised: 15 May 2020 / Accepted: 20 May 2020 / Published: 23 May 2020
(This article belongs to the Section Physical Sensors)
We report on the development of a method for measuring the permittivity and conductivity of fluids inside a sealed tank (or a pipe) by using an embedded coaxial probe. Permittivity and conductivity in the frequency range 600 MHz to 6 GHz are determined from measurements of a complex reflection coefficient by using a vector network analyser (VNA) that is connected to the embedded probe via a coaxial cable. Substitution methods for calibration of an inaccessible probe are studied in this paper. These require the VNA with attached cable to be calibrated prior to connecting the cable to the embedded coaxial probe. Measurement of permittivity and conductivity of fluids inside sealed tanks and pipes is needed for monitoring industrial processes, such as fermentation. The authors’ requirement, however, was to allow monitoring of a tissue-equivalent liquid that is contained inside a sealed tank. This tank is a component of a commercial system for rapid, multiple-band measurement of the specific absorption rate (SAR) of mobile phone handsets. Monitoring of permittivity and conductivity is needed to ensure compliance with international standards for SAR measurement. The paper also presents data for a new broadband (600 MHz to 6 GHz) tissue-equivalent liquid that is based on an oil-in-water emulsion. It is demonstrated that over an extended period of time, the liquid is stable, and an embedded coaxial probe enables its properties to be monitored with the required accuracy. View Full-Text
Keywords: dielectric measurement; process monitoring; open-ended coaxial probe; specific absorption rate (SAR); tissue-equivalent materials dielectric measurement; process monitoring; open-ended coaxial probe; specific absorption rate (SAR); tissue-equivalent materials
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Gregory, A.P.; Quéléver, K.; Allal, D.; Jawad, O. Validation of a Broadband Tissue-Equivalent Liquid for SAR Measurement and Monitoring of Its Dielectric Properties for Use in a Sealed Phantom. Sensors 2020, 20, 2956.

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