New Measurement method of whole body SAR by using Wheeler Cap method Takuji Arima*, Takashi Imamura, and Toru Uno Faculty of Engineering, Tokyo University of Agriculture and Technology *t-arima@cc.tuat.ac.jp Abstract In this paper a new measurement technique for whole body SAR of small phantom is proposed. The method is based on Wheeler cap method. Wheeler cap method is originally used for antenna efficiency measurement. In recent years, mobile phones are widely used. It is considered that a part of the radiated electromagnetic wave by mobile phones is absorbed into the human body. A lot of studies are accomplished about the interaction of the human body and the electromagnetic wave from such a background. The thermal effects are dominant in the microwave frequency region. And the quantity of energy absorption is evaluated by using SAR (Specific Absorption Rate). In order to measure the SAR from electric fields, electric field sensors are used. Optical fiber thermometer or Thermo camera are used to measure the SARs from a temperature rise. However, these methods are needed a huge measurement time to measure whole body SAR. On the other hand, it is necessary to measure the whole body SARs. However, it is not easy to measure the whole body SARs by the conventional technique. In this study, we will use wheeler cap method to measure the whole body SAR. The effectiveness of the method is confirmed by experimentally and numerically. 1. Introduction In recent years, communications equipment including a personal mobile phones which used in a human body neighborhood increases. The mobile phones are often used in a neighborhood of human body. It is considered that a part of the radiated electromagnetic wave by mobile phones is absorbed into the human body. In order to analyze interaction between electromagnetic wave and human body a lot of research have been performed. The quantity of energy absorption is evaluated by using SAR. SAR can be obtained by electric field as [w/kg] (1) ρ SAR σ 2 E = Where ρ is density, E is electric field (rms), σ is conductivity. There are three types of SAR measurement techniques, one of which is point SAR measurement technique. Point SAR can be measured easily by using electric field probe or temperature sensor. In the case of using temperature sensor, SAR can be estimated by [w/kg] (2) Where c is specific heat, ΔT is temperature elevation, Δt is heating time. Another type of SAR measurement techniques is surface SAR distribution. The surface SAR distribution can be measured by using thermography camera. Last SAR measurement technique is whole body SAR. Whole body SAR is total absorption power of target as human body. In order to measure whole body SAR, some techniques have been proposed. One of techniques is using electric field probe and scanning it. This technique can apply for only liquid type target as liquid phantom because the probe cannot scan if the target is solid. Another method is measuring total radiated power (TRP). A radiated power is absorbed by the human body. Therefore a part of radiated power is disappearing due to absorption by the human body. If TRP and input power of the antenna are known then whole body SAR can be measured by comparing these powers. This techniques is well known as measurement of antenna efficiency. However, large-scale equipment is required to measure TRP as 3-dimensional field scanner. Furthermore, huge measurement time is needed due to 3-dimensinal TRP measurement. Therefore a measurement technique of whole body SAR is not established yet. On the other hand, Wheeler cap method is well known as antenna efficiency measurement technique. Reflection coefficient of the antenna and shielding cap are used to measure antenna efficiency in the Wheeler cap method. This technique not requires large-scale equipment. In this paper, a new measurement technique of whole body SAR is proposed. The technique is using wheeler cap method. 978-1-4244-6051-9/11/$26.00 ©2011 IEEE