A study of electromagnetic radiation and specific absorption rate of mobile phones with fractional human head models

Abstract

The specific absorption rate (SAR) value is a key parameter in defining the energy absorbed by the human head and body under electromagnetic (EM) radiation. It is known that the complex configuration of the mobile phone antenna with the human head modeling makes the evaluation of the SAR extremely complicated; this result in requiring high computational resource and long simulation time in numerical modeling. The theme of this thesis is to examine the electromagnetic radiation and SAR of mobile phones with fractional human head models. The evaluation of SAR induced in the head models in this thesis starts off with a simple monopole antennae using finite-difference time-domain (FDTD) method. This numerical analysis on the EM radiation and the SAR due to the monopole antenna installed on the mobile phone casing with the presence of fractional human head models is presented aiming at reducing the simulation computational time in the numerical analysis. Initial results have indicated that the idea of using fractional phantom head model can be used for an efficient SAR analysis. The common antenna in modern mobile communication applications falls into two categories - the external helical antenna and the internal patch antenna. Helical antenna consists of a small wire spring, and the patch antenna mainly consists of a patch and a ground plane. These antennas have been commonly adopted in the mobile applications in recent years. The numerical investiga tion of the EM radiation and the SAR induced in the human head because of both antennas together with various fractional phantom head models is also presented in this thesis. Results have indicated the feasibility of the fractional phantom head model for the SAR evaluation in most common types of mobile antennas. Measurements have also been carried out, and the MapSAR measurement system is used to verify the SAR value induced in the fractional phantom head models. Three types of antennas including the monopole, helical, and patch antenna are examined. The comparison of the measured and simulated SAR value on the fractional spherical phantom due to these antennas is presented. Both simulation and measurement results have shown a good agreement on the SAR analysis. Finally, the fractional head model is also examined in the mobile antenna design’s applications, the relationship between various ground plane configurations of mobile patch antennas and the SAR value are studied. It is found that the SAR value is sensitive to the size of the antenna ground plane; it can be summarized that the fractional phantom head model can be adopted in the mobile phone design analysis. In general, a study of the EM radiation and the SAR of mobile phones with different numerical human head models, including different shapes and different fractional models, are examined in this thesis. It is summarized that the fractional phantom model can be considered as an alternative phantom head model in the SAR analysis.

Date of Award	15 Jul 2008
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Sai Wing Peter LEUNG (Supervisor)