STUDY ON MEASUREMENT METHOD OF POWER ABSORPTION BY HUMAN BODY IN THE VICINITY OF PORTABLE TELEPHONE

在设计天线时，测量人体在移动电话和个人手持电话系统等无线电设备附近的吸收功率是非常重要的。在本研究项目中，提出了一种基于方向积分法测量天线和人体模型沿方位角方向旋转，接收天线沿仰角方向旋转的天线附近人体吸收功率的方法，并获得了以下结果：(1)用该方法测量了半波长偶极子天线的辐射效率，并与随机场法的结果进行了比较。结果表明，该方法的精度高于随机场法。(2)采用微机控制旋转装置，研制了高速自动测量系统。(3)测量了安装在便携式电话机机身上的半波长偶极子天线和单极子天线在COST 244头影附近的辐射效率。将计算结果与时域有限差分法的数值结果进行了比较，验证了所提方法的有效性和较高的精度。本文还指出，球面光体的吸收功率比立方光体的吸收功率小。(4)基于Yagi-Uda天线的原理，设计了单极子阵列天线和低轮廓环形阵列天线，采用时域有限差分法降低了天线的吸收功率。数值和实验结果表明，所设计的天线的辐射效率高于一般的单极天线。

It is very important to measure the absorbed power by human body in the vicinity of radio equipments such as the portable telephones and the personal handy phone systems (PHS) when designing antennas. In this research project, a method based on the pattern integration method for measuring the power absorption by the human body in the vicinity of antenna, in which the antenna and the human model are rotated along azimuth direction and the receiving antenna is rotated along the elevation direction, has been proposed and following results have been obtained.(1) The radiation efficiency of the half-wavelength dipole antenna has been measured by using the proposed method and compare with the results by the random field method. It has been shown that the accuracy of the proposed method is higher than that of the random field method.(2) High-speed and automatic measuring system has been developed by controlling the rotators by personal computer.(3) The radiation efficiency of the half-wavelength dipole antenna and a monopole antenna mounted on the body of portable telephone in the vicinity of the COST 244 head phantoms has been measured. The results have been compare with the numerical results obtained by the FDTD (Finite Difference Time Domain) method confirming the validity and the high accuracy of the propose method. It has been also pointed out that the absorption power of the spherical phantom is smaller than that of the cubic phantom.(4) A monopole array antenna based on the principle of the Yagi-Uda antenna and a low-profile loop array antenna have been designed to reduce the absorbed power by using the FDTD method. It has been confirmed numerically and experimentally that the radiation efficiency of the designed antennas is higher than the usual monopole antenna.