EVALUATION OF THE SAR DISTRIBUTION IN THE HUMAN HEAD FOR CELLULAR PHONES USED IN A PARTIALLY CLOSED ENVIRONMENT

The purpose of this paper is to calculate the specific absorption rate (SAR) distribution in a human head exposed to the electromagnetic fie ld emitted from a handheld cellular phone operating in the 900 MHz ran ge in a partially dosed environment, The environment could be, for exa mple, the interior of a car, a condition of exposure which is largely diffused nowadays, The presence of reflecting surfaces near the phone modifies the current distribution on, and the emitting properties of, the phone antenna, Therefore, the distribution of the absorbed power i nside the head is different from that absorbed in the free space expos ure condition, The finite-difference time-domain (FDTD) method has bee n used to evaluate the SAR in a realistic anatomically based model of the human head for different antenna-handset configurations and for di fferent antenna-head distances, The environmental effects have been si mulated through partially or totally reflecting walls located in vario us positions with reference to the phone. It is found that the presenc e of a horizontal reflecting wall over the head decreases the SAR valu es in the part of the head directly exposed to the phone antenna, whil e it increases the SAR values in the part not directly exposed. On the contrary, the presence of a vertical wall, located in proximity of th e phone and parallel to it, raises the SAR values everywhere into the head.