Abstract
The U. S. Federal Communication Commission (FCC) has required the routine specific absorption rate (SAR) evaluation of portable telephones since 1997. The applicable SAR limit is 1.6W/kg as averaged over any one gram of tissue, defined as a tissue volume in the shape of a cube. Because of the irregular surface of the human head and tissue heterogeneity, computing the one-gram averaged spatial peak SAR in the shape of a cube is not so easy. A lack of standardized procedure for computing the one-gram averaged spatial peak SAR is resulting in confusion in the SAR assessment. In this paper, the SAR in an anatomically based human head model is computed using the finite-difference time-domain (FDTD) method, and the uncertainties of different four kinds of one-gram average procedures are evaluated numerically. The results show that an uncertainty up to 2.4 times may exists at 900 MHz. A nearly 1×1×1 cm cube with a mass of just one gram, but not containing the air cells, seems to be reasonable for the one-gram average of SARs.
