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Calibration of reference antennas for vector measurements of SAR

Bownds, D J; Gregory, A P; Revillod, G; Cox, M G; Allal, D (2020) Calibration of reference antennas for vector measurements of SAR. NPL Report. National Physical Laboratory. TQE 15

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Abstract

Vector-based instrumentation for the determination of Specific Absorption Rate (SAR) uses measurements of the complex E-field inside a phantom at multiple locations. Re-construction algorithms are used to calculate the SAR and its peak spatial value. The required measurements can be made by using
an E-field vector probe that is controlled by a robot, or by using a static array of vector probes (for example, dipole antennas and receivers). The latter approach potentially offers much reduced measurement times, which is particularly advantageous for type-approval tests on smart phones as these can have 30 or more transmitting modes. To enable traceable measurement of SAR, an array-based system requires calibration data for its individual antennas,
which can be obtained by exposing the individual antennas to a characterised complex E-field from a stable antenna (which will be referred to as a reference antenna). This report describes the process for characterising a reference antenna: traceable mapping of complex E-fields inside a liquid phantom which
is illuminated by the antenna from beneath. The measurements of complex E-field were made by using an electrooptic probe that has been calibrated by using a traceable waveguide system.

Item Type: Report/Guide (NPL Report)
NPL Report No.: TQE 15
Subjects: Electromagnetics > Electromagnetic Materials
Divisions: Electromagnetic & Electrochemical Technologies
Publisher: National Physical Laboratory
Identification number/DOI: 10.47120/npl.TQE15
Last Modified: 05 Jul 2021 10:15
URI: http://eprintspublications.npl.co.uk/id/eprint/9034

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