21/10/2011

Chung-Huan Li, Mark Douglas, Erdem Ofli, Benoit Derat, Sami Gabriel, Nicolas Chavannes, and Niels Kuster, IEEE Transactions on Antennas and Propagation, Volume 60, Issue 2, pp. 1066–1074, February 2012, online October 21, 2011

The influence of the user’s hand holding a mobile phone to the ear on the peak spatial-average Specific Absorption Rate (psSAR) averaged over any 1g and 10g of tissue in the head is investigated. This study is motivated by recent reports that found substantial increases in psSAR by the presence of the hand in some cases. Current measurement standards prescribe the measurement of SAR in a head phantom without a hand present. The mechanisms of interaction between the hand and mobile phone models are studied. Simulations and measurements at 900 and 1800 MHz have been conducted to complement the understanding of the hand grip parameters leading to higher SAR in the head. Numerical simulations were conducted on four mobile phone models, and parameters such as the palm-phone distance and hand position were varied. Measurements of 46 commercial mobile phones were made, and the maximum psSAR with different hand positions and palm-phone distances was recorded. Both simulations and measurements have found increases in the psSAR in the head of at least 2.5 dB due to the presence of the hand. Furthermore, the psSAR is sensitive to the hand grip, i.e., the variations can exceed 3 dB.

The scientific and technical impact of the study can be summarized as:

• The paper represents the largest scientific study to date of the influence of the user’s hand on SAR in the head.
• Significant and reproducible psSAR increases in the head are possible when the hand holding a mobile phone is included. This challenges the previously held assumption that the presence of the hand reduces the SAR in the head.
• This study also is an important input for the international measurement standard committees as they have not decided yet how to consider  the hand in psSAR assessment.

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