Numerical and Experimental Methods for Determination of SAR and Radiation Patterns of Cellular Telephones

摘要

The finite-=difference time-domain (FDTD) method has been used to caluclate the mass-normalized rates of electromagnetic energy absorption (specific absorption rates or SARs) in an anatomically-based model of the human head and neck for wireless telephones operatig at 835 and 1900 MHz using a variety of antennas such as a monopole, helix, helix-monople whip or stacked-patch antenna. The handsets are assumed to be held against the ear at varying angles of 0deg, 20deg, 30deg and 45deg relative to the vertical to obtain the SAR distribution in an MRI-based model of the human head and neck where different tissues have been identified for each of the subvolumes or voxels of dimensions 1.974x1.974x3.0 mm along the three orthogonal axes. Such simulations allow determination of peak 1-g SAR which for all new personal wireless devices must comply with the RF safety guidelines approved by the U.S. Federal Commmunications Commission. The electromagnetic fields calculated at the boundaries of the FDTD simulation space can also be used to determine the radiation patterns of these personal wireless devices in the presence of the human head by the use of near-to-far field transformation. This numerical method can, therefore, be used as a tool for design of wireless devices wiht desired radiation patterns and reduced ocupling to the human body.