A multi-grid finite-difference time-domain (FDTD) method was applied for numerical dosimetry analysis in the human head for 5 GHz band portable terminals. By applying fine FDTD grids to the volumes in the human head where the highest electromagnetic (EM) absorption occurs and coarse grids to the remaining volumes of the head, the spatial peak specific absorption rate (SAR) assessment was achieved with a less computation memory and time. The accuracy of applying the multi-grid FDTD method to the spatial peak SAR assessment was checked in comparison with the results obtained from the usual uniform-grid method, and then the spatial peak SARs for three typical situations of a person using a 5.2 GHz band portable terminal were calculated in conjunction with an anatomically based human head model.

This paper presents a dosimetric analysis in an anatomically realistic human head model for a helical antenna portable telephone by using the finite-difference time-domain (FDTD) method. The head model, developed from magnetic resonance imaging (MRI) data of a Japanese adult head, consists of 530 thousand voxels, of 2 mm dimensions, segmented into 15 tissue types. The helical antenna was modeled as a stack of dipoles and loops with an adequate relative weight, whose validity was confirmed by comparing the calculated near magnetic fields with published measured data. SARs are given both for the spatial peak value in the whole head and the averages in various major organs.