FDTD Analysis of Electromagnetic Interaction between Portable Telephone and Human Head

Masao TAKI  So-ichi WATANABE  Toshio NOJIMA  

IEICE TRANSACTIONS on Electronics   Vol.E79-C    No.10    pp.1300-1307
Publication Date: 1996/10/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section INVITED PAPER (Special Issue on Electromagnetic Theory-Foundations and Applications)
near-field exposure,  biological effect,  specific absorption rate,  FDTD method,  cellular telephone,  

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Finite-difference time-domain (FDTD) analysis is performed to evaluate the distributions of specific absorption rate (SAR) in a human head during use of a handheld portable telephone. A heterogeneous head model has been assumed which is comprised of 273 108 cubic cells 2.5 mm on a side, with the electrical properties of anatomical equivalents. A handset model has been assumed to be a metal box with either a quarter-wavelength monopole or a half-wavelength dipole operating at 900 MHz or 1.5 GHz. The maximum local SARs in the head are evaluated under various exposure conditions. The dependence of the maximum local SARs on the difference in the structures or parameters of the model, i.e. the distance between the antenna and the head, the heterogeneity of the head, the antenna type, the volume of the smoothing region of the local SAR value, skin electrical constants, and the presence or absence of auricles, are examined. It is shown that the heterogeneity of the head barely affect the maximum local SAR when the telephone is located sufficiently close to the head. It is also shown that the electrical constants of skin which has lower conductivity provide the lower maximum local SAR in the head while the maximum local SAR within the brain is not significantly affected. The auricle which lies in closest proximity to the antenna is shown to have significant effect on the maximum local SAR. It is suggested that the presence of the auricle enhances the maximum local SAR by a factor that is 1.7-2.4 larger than the model without auricles.