Numerical Study of Maximum Peak Spatial SAR Reduction in a Mobile Phone
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ORIGINAL ARTICLE
Numerical Study of Maximum Peak Spatial SAR Reduction in a Mobile Phone Jisu Lee1 · Seungyong Park1 · Ae‑Kyung Lee2 · Hyung‑Do Choi2 · Kyung‑Young Jung1 Received: 28 April 2020 / Revised: 9 June 2020 / Accepted: 8 July 2020 © The Korean Institute of Electrical Engineers 2020
Abstract The government regulates specific absorption rate (SAR) levels of mobile phones and beyond that limit, mobile phones are not available on the market. The SAR measurement for a specific anthropomorphic mannequin (SAM) phantom is performed for four different positions and all 1-g peak spatial SAR values should meet the requirement. In this work, we propose a novel approach to reduce the maximum 1-g peak spatial SAR value by balancing the SARs. This SAR balancing can be achieved by modifying ground current distributions. Numerical examples are employed to validate our approach. It is observed that the maximum 1-g peak spatial SAR value can be reduced by 40% compared to the case without modifying ground current distributions. Keywords Mobile phone · Specific absorption rate (SAR) · SAM phantom · Finite-difference time-domain (FDTD) method
1 Introduction When the output power exceeds 20 mW and the center point of the electromagnetic wave emission is located within 200 mm from the human body in the usual usage status, the specific absorption rate (SAR) test should be tested. There is a maximum allowable level for the peak spatial specific absorption rate. For examples, the 1-g peak spatial SAR limit for a human head is 1.6 W/kg over a l g mass in South Korea and U.S and 2 W/kg over a 10 g mass in Europe and Japan. The SAR values are measured at four positions for head and the 1-g peak spatial SARs should satisfy the limit of the standard for all of these four positions. When the 1-g peak spatial SAR level of a mobile phone exceeds that value, it cannot be sold in the market, and thus various SAR reduction techniques were actively studied. For example, a ferrite sheet can be used to reduce the SAR by attaching it to conducting bodies in mobile phones [1]. In addition, metamaterials can be employed to reduce the SAR by * Kyung‑Young Jung [email protected] 1
Department of Electronics and Computer Engineering, Hanyang University, Seoul, Korea
Radio Technology Research Department, Electronics and Telecommunications Research Institute (ETRI), Daejeon, Korea
2
arranging split ring resonators (SRRs) periodically between the antenna and the head [2] or by using artificial magnetic conductor (AMC) as a reflector [3]. Moreover, there is a method called the compensation method, in which the SAR is reduced by canceling the electromagnetic fields of the main handset radiator with the auxiliary antenna located between the head and the handset radiator [4, 5]. It is also noting that a parasitic radiator was proposed to reduce the SAR by changing the current distribution [6]. In this work, we propose a novel idea to reduce the maximum 1-g peak spatial SAR value by balancing 1-g peak spatial SAR values. Differently from the
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