Specific Absorption Rate (SAR) Induced in Human Heads of Various Sizes When Using a Mobile Phone Adel Z. El Dein Alaeddin Amr Abstract - This paper analyzes the specific absorption rate (SAR) induced in human head model of various sizes by a mo- bile phone at 900 and 1800 MHz. Specifically the study is con- sidering in SAR between adults and children. Moreover, these differences are assessed for compliance with international safe- ty guidelines. Also the effects of these head models on the most important terms for a mobile terminal antenna designer, namely: radiation efficiency, total efficiency and directivity, are investigated. Index Terms—Human Head, Mobile Phone, SAR. I. INTRODUCTION In recent years, much attention has been paid to health implication of electromagnetic (EM) waves, especially hu- man head part, which is exposed to the EM fields radiated from handsets. With the recent explosive increase of the use of mobile communication handsets, especially the number of children using a mobile phone, that develops many ques- tions about the nature and degree of absorption of EM waves by this category of public as a function of their age and their morphology. For this reason the World Health Organization (WHO) has recommended to undertake re- search studies on this subject [1]. This paper investigates the effects of head models of various sizes on the most impor- tant terms for a mobile terminal antenna designer, namely: radiation efficiency, total efficiency and directivity; and also on the Specific Absorption Rates (SAR) which are induced in them. For this purpose, a comparison is performed con- cerning those parameters between an adult human head and some children heads obtained as a percent of an adult human head. The results are obtained using an electromagnetic field solver employing the Integral Equations method [2]. The SAR is the most appropriate metric for determining EM effect exposure in the very near field of a Radio Frequency (RF) source [3-7]. The local SAR (W/kg) at any point in the human head is defined as:   2 2 E SAR  (1) where E is the peak amplitude of the electrical field in the human head tissue (V/m), σ is the tissue conductivity (S/m) and ρ is the tissue density (kg/m 3 ). The SAR over a mass of 10g and 1g in the head and the other parameters of the mo- bile antenna are determined in each case. II. MODELING OF HUMAN HEAD For this study, five head models are used namely: that of an adult and other children human heads of sizes; 95%, 90%, 85%, and 80% of the adult head size (which of size 100%), as they are shown in fig. (1). Each head model consists of shell of skin tissue which is filled with a liquid of brain properties. For simulation of the EM fields in the human head, the appropriate parameters for the conductivity σ (S/m), the relative permittivity  r and the tissue density ρ (kg/m 3 ) of all different materials used for the calculation must be known. Additionally, the frequency dependence of these parameters must be considered and chosen appro- priately. A recent compilation of Gabriel et al. covers a wide range of different body tissues and offers equations to de- termine the appropriate dielectric values at each desired frequency [8]. 100% 95% 90% 85% 80% Fig. 1 The description of the various sizes human head models Table I shows the real part of the dielectric permittivity ε r , conductivity σ (S/m), and mass density ρ (kg/m 3 ) of tissues used in the simulations at 900 and 1800MHz. Table II Manuscript received February 24, 2010. Paper no. ICWN_14. Adel Z. El Dein is with the Department of Electrical Engineering, High Institute of Energy, South Valley University, Aswan 81258, Egypt (e-mail:azeinm2001@hotmail.com). Alaeddin Amr is with faculty of Computer Engineering and IT Al-Hussein Bin Talal University P.O. Box 20 Ma'an Jordan (e-mail:amroru@ hotmail.com). Proceedings of the World Congress on Engineering 2010 Vol I WCE 2010, June 30 - July 2, 2010, London, U.K. ISBN: 978-988-17012-9-9 ISSN: 2078-0958 (Print); ISSN: 2078-0966 (Online) WCE 2010