Evaluation of Wireless Resonant Power Transfer Systems With Human Electromagnetic Exposure Limits

Andreas Christ, Mark G. Douglas, John Roman, Emily B. Cooper, Alanson P. Sample, Benjamin H. Waters, Joshua R. Smith and Niels Kuster, IEEE Transactions on Electromagnetic Compatibility, Volume 55, Issue 2, pp. 265-274, April 2013, online October 25, 2012

Wireless power transmission (WPT) systems using adaptive and tightly coupled resonant coils can efficiently transmit power of 100 W or more over up to a few meters distance. They typically operate at frequencies between 0.1 and 10MHz. Since they generate reactive fields of high field strength, they may violate the reference levels for human exposure and therefore regulators requests demonstration of compliance with the basic restrictions defined in SAR, induced currents and electric fields. In this paper, we investigated the exposure of a generic representative wireless power transfer system. Anatomical high-resolution models of adults and children are used to assess the whole-body and the peak spatial average SAR, In addition, a generic body phantom is proposed for experimental compliance testing.

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

  • WPS systems are not intrinsically compliant with the safety guidelines.
  • The methodology applied is suited for demonstration of compliance for any WPS and the results could also be used to derive a specific product standard for WPS.
  • Special considerations are need for persons with implants.
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