EXPERIMENTAL AND NUMERICAL EVALUATION OF SAR REDUCTION IN A HUMAN HEAD DUE TO RF SHIELDS DEVELOPED

Abstract

The use of mobile handsets has experienced exponential growth. It is known that exposure of the human body to Electromagnetic Radiation (EMR) from handsets leads to adverse health effects. Specific Absorption Rate (SAR) is one of the important criteria to evaluate the degree of the health hazard. In this thesis study has been done as an effort to design of a suitable ferrite sheet attached to a handset in reducing the SAR to a human head. Three samples one from Hexagonal ferrite (Ba3Mn(2_.,)Zn,,Fe24O41) and two from Spinel ferrite Ni(l_a)ZnoFe2O4 have been developed by dry attrition sintering method at different frequencies. Five different shapes and sizes of the shields from each prepared sample have been made to reduce SAR in head by attaching it externally to handset. To see the effect of the RF shields, experimental results have been taken for brain or muscle tissue simulated from ethanol and NaCl solution. For measurements head made from fiber glass and conducting box with (handset) quarter wave monopole antenna has been taken. SAR has been measured with and without shield attached to handset for different interest of parameters. SRF (SAR Reduction Factor) is used as the effectiveness of the shields. To numerically evaluate the performance of the RF-shield, FDTD method has been used. SAR has been calculated for homogeneous and inhomogeneous head models to see the effectiveness of RF shields