ISMOT 2011, June 20 - 23, Prague, Czech Republic, EU The Effect of the Water on the Interaction between Human Head Model and Dipole Antenna (900MHz) Mohamed Nabil Srifi *, Mohamed Essaaidi** * Telecommunications Systems Laboratory, National School of Applied Sciences (ENSAK) Ibn Tofail University, 14000 Kenitra, Morocco. Tel: +212 5 37 37 40 52; Fax: +212 5 37 32 92 00; E-mail: srifimn@yahoo.fr **LaSiT Department of Electrical Engineering, Faculty of Sciences Abdelmalek Essaadi University, Tetuan, Morocco; E-mail: essaaidi@ieee.org Abstract-The goal of much research into the biological consequences of exposure to RF/MW energy is the understanding of how such exposure may compromise the normal biological functioning of human beings. This exposure is influenced by several factors, such as the frequency of the signals, distance… People use their mobile and wireless communication devices (e.g. mobile phone) anywhere and any time. In this paper we study the effect of the presence of water layer at the surface of the mobile user’s head, which may affect the absorption of the radiated energy in the head. Index Terms- Biological effects, mobile phone, specific absorption rate (SAR). I. INTRODUCTION The study of biological effects of RF energy is a mature scientific discipline with a literature database that is extensive, but of uneven quality. The goal of much research into the biological consequences of exposure to RF/MW energy is the understanding of how such exposure may compromise the normal biological functioning of human beings. People use their mobile and wireless systems (e.g. mobile phone) anywhere and any time. For instance, during the summer, people in the beach use their mobile phones as usual and often after swimming. Then, their bodies are wet including the head, which is the mainly part exposed to the radiation during calls. A similar situation occurs when the man uses his mobile phone, with his hair wet, just after having taken its shower. In this paper, we attempt to study the effect of the presence of water layer in the surface of human head on the absorption of radiated energy by 900MHz dipole antenna. II. Specific Absorption Rate (SAR) Classical EM Exposure limits were simply defined by exposure quantities such as frequency, power densities and field strengths. But since 1982, the American National Standards Institute (ANSI) introduced a dosimetric approach for non-ionizing radiation referring to the same concept as in ionizing radiation protection [1]. The dose is defined as the energy absorbed per unit mass. Due to the complexity of the interaction mechanism between EM fields and human body, the dose concept was extended by defining the absorbed power per unit mass (W/kg) as the critical quantity for safety considerations rather than the absorbed energy per unit mass (J/kg). The amount of absorbed energy is quantified by the absorbed power per unit of exposed biomaterial mass, and it’s given by the specific absorption rate (SAR) which defines the incremental electromagnetic power ( dP ) absorbed by an incremental mass ( dm ) within a volume element ( dV ) with the specific mass density( ρ ) as follow: dP dP SAR dm dV ρ = = (1) The specific absorption rate can be determined by assessing the electric field in biological tissue (with the conductivity σ , and the mass density ρ ). The instantaneous or peak SAR value is proportional to the square of intensity of the electric field induced in the material, and the constant of proportionality increases with the conductivity of the material.