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Absorption Characteristics and SAR of a Lossy Sphere inside a Reverberation Chamber

This study presents an experimental approach to the analysis of absorption characteristics of a lossy dielectric object in a reverberant environment. The study used a canonically shaped water-filled sphere, convenient for Absorption cross-section ACS calculations (analytical or by simulations), and measured the internal temperature rise when exposed to RF radiation. All measurements were conducted in a reverberation chamber. The internal temperature rise due to EM absorption was used to calculate actual SAR, using the bio-heat equation. This was done at two discrete frequencies: 1 GHz and 1.8 GHz. ACS was derived experimentally from scattering parameters measured for a loaded and unloaded chamber. Measured ACS results were compared to the ones calculated analytically using Mie scattering theory, and to the ones calculated from SAR simulations using SEMCAD X, in the frequency range from 1 GHz to 8 GHz. The results show a good agreement, forming a basis for an experimental procedure that can then be used for other less canonical shapes. The results obtained for actual SAR in the reverberation chamber are indicative and can serve as a reference for further exposure studies.

absorption cross section; specific absorption rate SAR; lossy dielectric sphere; reverberation chamber

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