1 SAR Evaluation In Human Heads

Existing scientific data on absorption of electromagnetic fields in the human body during the use of mobile telephones are mainly based on measurements on phantoms and on simulations. Up to now it has been unclear if measurements in human tissue would lead to the same conclusions as evaluations in phantoms and simulations did. During this project, the specific absorption rate (SAR) was evaluated in the heads of five fresh cadavers. The evaluation was performed at the frequencies 433 MHz, 900 MHz, 1,300 MHz, 1,800 MHz and 2,450 MHz. We used dipole antennas at varying radiated powers. The emitted fields were unmodulated. Measurements were performed in the brain, the inner ears and the eyes of the heads. Evaluations were performed at two antenna positions: next to the ear (at 20 mm distance to the skull) and at 40 mm in front of the eye. The specific absorption rate was evaluated by performing measurements of the electric field strength in human tissue and also by measuring the temperature versus time during irradiation of the heads. The evaluation of the absorption rate requires the knowledge of the permittivity of the human tissue. Therefore permittivity and conductivity were examined in isolated samples of human brain, muscle and eyes before performing the SAR evaluation. At a radiated power below 1 W the limit of the specific absorption rate of the Austrian prestandard ÖNORM S1120 of 4 W/kg averaged over 1 gram tissue was not exceeded. A radiated power of 2 W led to SARs above the mentioned limits in some cases. For comparison reasons measurements of the SAR were also performed in phantom heads. We found good correspondence between the SAR values evaluated in the human heads and the phantom heads