Mechanisms of RF Electromagnetic Field Absorption in Human Hands and Fingers

Chung-Huan Li, Mark Douglas, Erdem Ofli, Nicolas Chavannes, Quirino Balzano, and Niels Kuster, IEEE Transactions on Microwave Theory and Techniques, Volume 60, Issue 7, pp. 2267–2276, July 2012, online June 26

The objective of this paper is to analyze the mechanisms of absorption of electromagnetic fields in the hand over the 900–3700 MHz frequency range. From this analysis, we calculate the envelope of the peak spatial specific absorption rate (psSAR) in the hand with respect to the psSAR limits. We use this analysis as a basis to determine whether a standardized test method using a flat phantom is conservative. Both plane waves and dipole antennas are used to investigate the patterns of RF absorption in hand and finger tissue models for far- and near-field exposures. The results demonstrate that absorption enhancements are found in the hand in some circumstances that are not present in a flat phantom. Enhancements of several decibels are observed, depending on the model parameters. Guidance is developed to conservatively estimate the exposure in the hand based on flat phantom measurements.

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

  • The mechanisms of electromagnetic field absorption in the hands and fingers have been analyzed in detail.
  • Slab and cylindrical dielectric models were developed to understand the enhancements observed in anatomical models.
  • Models for the absorption as a function of frequency, length and diameter have been developed in order to determine the envelope of psSAR in the hand and fingers.
  • We have shown that in some circumstances, absorption enhancements are found in the hand and finger models that are not present if measurements are conducted in a large flat phantom.
  • International committees developing psSAR measurement procedures will benefit from the knowledge of the absorption mechanisms and conservative assessment principles provided in this paper.
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