Electromagnetic absorption in the human head from experimental 6-GHz handheld transceivers

We have used a new millimeter-resolution MRI-based model of the human body to calculate the electromagnetic absorption in the head and neck for three experimental Yagi antennas suggested for the handheld transceivers of a proposed 6-GHz personal communication network (PCN) system, The SAR distributions are obtained with a resolution of 1.974 x 1.974 x 1.5 mm for the transceivers that are held against the ears and tilted forward by 33 degrees. The finite-difference time-domain technique is used to calculate the EM fields and SAR's for the transceiver, antenna, and head and neck coupled region that is divided into 158 x 84 x 188 or nearly 2.5 million cells. The highlights of the numerical calculations are verified by means of a head-shaped experimental model made of tissue-equivalent materials simulating the electrical properties (epsilon(r),sigma) of skull, brain, muscle, eyes, and ears developed for use at 6 GHz. Because of the proximity to the antenna, the highest SAR's are obtained for the upper part of the ear, For a planned radiated power of 0.6 W, the peak SAR's averaged over any 1 g of tissue defined as a tissue volume in the shape of a cube are on the order of 0.5-1.0 W/kg for two of the proposed antennas and considerably higher (2.06 W/kg) far the third antenna using a narrower off-axis reflector, Low SAR's for the first two antennas are likely due to the shielding provided by the relatively wider strip reflector plates used for these antennas.