TABLE I: ELECTRICAL PROPERTIES OF THE NaCl SOLUTION USED IN EQUIVALENT ANTENNAS WITH CONCENTRATION OF 2.7 % f [MHz] 30 40 45 60 80 100 εr 86.4 85.2 84.7 83.5 81.7 80.7 σ[S/m] 4.04 4.05 4.06 4.07 4.09 4.09 Comparison of Induced Ankle Currents of the Human-Body Equivalent Antennas and Anatomically Human Models Exposed to Nearby Monopole Antennas Ally Y. Simba 1 , Akira Itou 1, 2 , Lira Hamada 1 , Soichi Watanabe 1 , Takuji Arima 1, 2 , and Toru Uno 2 1 National Institute of Information and Communications Technology, Tokyo, Japan 2 Tokyo University of Agriculture and Technology, Tokyo, Japan Email: simba@nict.go.jp Abstract In this paper, the induced ankle currents of the liquid-type human-body equivalent antennas are compared to those of their corresponding Japanese adult male and female models when exposed to monopole antennas placed at a distance of 3 m away. The purpose is to determining if they will be in good agreement like the case of plane wave exposure from which they were designed. The investigation of the monopole antennas exposure is important, because they have been used to provide experimental validation of the performance of the equivalent antennas. Our results indicate that good agreement in induced ankle current is obtained for the frequencies above 45 MHz. This may be explained by the fact that at the frequencies above 45 MHz, at 3 m distance away, the equivalent antennas appear to be at far fields of the monopole antennas, at which the fields becomes almost like those of the plane wave. 1. Introduction At Very High Frequency (VHF) bands (30-300 MHz) the power absorption by the human body due to RF exposure reaches maximum values. This is because the whole-body resonant absorption frequencies lie within this region [1]. It is known that large current flows at the ankle if the human body stands on the ground at the whole-body resonant condition. The local SAR around the ankle (SAR ankle) can be estimated from the induced ankle current (I_ankle) and the equivalent section area of the ankle (A_ankle), i.e., SAR_ankle = (I_ankle/A_ankle)2/sigma. As a result, the induced ankle current is used as an additional exposure limit in the VHF bands in the ICNIRP and IEEE guidelines. The liquid-type human-body equivalent antenna that can be used for measuring these currents has been previously proposed [2]. The antennas consist of acrylic rectangular blocks and metal plate, which are filled with NaCl solution and connected together using conducting pins. While we have conducted detail investigation of the induced currents of the equivalent antennas using plane wave exposure, and validated our numerical calculations using experimental results obtained when the antennas are irradiated with nearby monopole antennas, there have been no investigations to compare the induced ankle currents of the equivalent antennas and their corresponding human model so far. This is important because, we have been using monopole exposures to validate our numerical assumptions. In this paper we consider equivalent antennas for adult Japanese male and female models [3]. The induced ankle currents are calculated using non-uniform mesh FDTD analysis to minimize computer resources [4]. 2. Equivalent Antennas and Method of Calculation 2.1 Equivalent Antennas Fig.1 shows the structures of the liquid-type human-body equivalent antennas for the adult male and female Japanese models [3]. The equivalent antenna for the adult male model is made up acrylic blocks placed on top of metal plate; they are connected together using conducting pins. Antenna for female model is made up of 5 blocks. The antennas are filled with NaCl whose electrical properties are obtained by measurements. The electrical properties of the liquid used are listed in Table I. It should be noted here that, the electrical properties of the human models were derived from Gabriel reports [5]. 978-1-4244-6051-9/11/$26.00 ©2011 IEEE