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26/03/2013

Analysis of Mobile Phone Design Features Affecting Radio-frequency Power Absorbed in a Human Head Phantom

Sven Kühn, Michael Kelsh, Niels Kuster, Asher Sheppard, and Mona Shum, Bioelectromagnetics, Volume 34, Issue 6, pp. 479–488, September 2013, online March 26, 2013

Accurate dosimetric models are a key factor in epidemiological studies that aim to assess human exposure to radio-frequency electromagnetic fields. The most dominant source of localised exposure to radio-frequency electromagnetic fields is the mobile phone on the body or operated at the head. The actual dose of exposure can vary by orders of magnitude depending on the type of mobile phone and communication technology, which results in inaccurate prediction of the exposure when simplified models, e.g., call duration, are applied as dosimetric quantities. 

In this study, we analysed the US FCC SAR compliance test database statistically to identify proxies for human exposure based on certain mobile phone design parameters. The aim of this analysis was to develop a simple yet accurate dosimetric model by identifying the mobile phone design parameters that insignificantly impact human exposure (simplification) and the design parameters that exhibit significant effects (accuracy). Service technology accounted for the greatest variability in compliance test specific absorption ratio (SAR) values, which ranged from highest for AMPS through CDMA, iDEN, and TDMA, to lowest for GSM. However, the dominant factor for SARs during use is the time-averaged antenna input power, a factor that is largely defined by the communication system, which may be much less than the maximum power used in testing, e.g., the GSM phone average output can be higher than CDMA by a factor of 100. Phone shape, antenna type, and phone orientation were found to be significant but only on the order of up to a factor of 2 (3 dB). Other tested factors showed smaller or insignificant impact on the differential dose from mobile phones operated at the human head. For the most significant factors, communication system and average antenna input power, we developed a novel simple formula to predict the actual induced dose in the human head based on easily accessible design parameters of the mobile phone.

The scientific impact of this study can be summarized as:

  • This is the first statistical evaluation of a large-scale SAR measurement data base to identify mobile phone design parameters as dosimetric proxies for epidemiological studies.
  • We found that the main distinguishing design factor with respect to spatial peak SAR is the mobile phone communication system.
  • A novel simplified exposure prediction model based on the communication system parameters, frequency, and output power was developed and validated.
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