SAR Distributions in a Head Model The development of cellular telephones and mobile communication systems has led to a growing awareness of the vital role that wireless systems play in communication networks and the biological effects of EM fields on users. Since cellular hand phones are operated in close proximity to human heads while in use, there has been increasing public concern about the health effects of the human head exposed to EM energy emitted from mobile handset antennas. | Spheroidal Wave Functions in Electromagnetic Theory Le-Wei Li Xiao-Kang Kang Mook-Seng Leong Copyright 2002 John Wiley Sons Inc. ISBNs 0-471-03170-4 Hardback 0-471-22157-0 Electronic 7 SAR Distributions in a Spheroidal Head Model INTRODUCTION The development of cellular telephones and mobile communication systems has led to a growing awareness of the vital role that wireless systems play in communication networks and the biological effects of EM fields on users. Since cellular hand phones are operated in close proximity to human heads while in use there has been increasing public concern about the health effects of the human head exposed to EM energy emitted from mobile handset antennas. To avoid the harmful effects of EM fields radiated by mobile phones designers of hand-phone antennas must be able to develop highly efficient low-profile antennas that can be mounted on handheld transceivers and operated in the proximity of human tissues. To evaluate potential health effects the specific absorption rate SAR is normally used to evaluate the rates of EM energy deposition in animal or human tissues. An important motivation for researchers is to gain a detailed understanding of the EM field distribution and power absorption distribution inside the human head 138 139 . There exist a variety of techniques that can be used to perform the required analysis of SAR deposition in human heads each with its own strength and weakness. In the analysis the model obtained from medical imaging serves as a realistic model but requires a lot of computational time as in the methods of finite element 140 finite difference MIMS and moments 146 147 . To increase computational speed the spherical human head model is also often adopted as an idealized representation of a real biological human head in the analysis 148-151 but it is less accurate. 191 192 SAR DISTRIBUTIONS IN A SPHEROIDAL HEAD MODEL In view of the fact that the geometry of a human head can be better approximated by a .
