Temperature rise in the human head and brain for portable handsets at 900 and 1800

The purpose of this paper is to calculate temperature rises in an anatomically based model of the human head and brain for handset antenna at 900 and 1800 MHz. The specific absorption rate (SAR) is initially calculated with the use of the finite-difference time-domain (FDTD) method. The temperature rises in the human head and brain are then calculated by substituting the SAR into the bio-heat equation. The steady-state maximum temperature rises in the head and brain are determined through linear extrapolation of the peak average SAR. The averaged 1 g peak SARs in the head model are 1.590 W/kg at 900 MHz and 1.515 W/kg at 1800 MHz. The maximum temperature rises are 0.160 /spl deg/C in the head and 0.054 /spl deg/C in the brain at 900 MHz and 0.124 /spl deg/C, 0.044 /spl deg/C at 1800 MHz. Computed results show higher temperature elevation is obtained at 900 MHz in comparison to 1800 MHz and temperature increases rapidly within 3 min of phone time. In addition, after 7-8 minutes of phone time it reaches about 90 % of steady-state value and the steady-state condition in 30 minutes.