Near-field mapping system using fiber-based electro-optic probe for specific absorption rate measurement
Near-field mapping system using fiber-based electro-optic probe for specific absorption rate measurement
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DOI：
10.1093/ietele/e90-c.2.436
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发表时间：
2007-02-01
影响因子：
0.5
通讯作者：
Nagatsuma, Tadao
中科院分区：
文献类型：
--
作者：
Togo, Hiroyoshi;Shimizu, Naofumi;Nagatsuma, Tadao
我们已经开发了一个近场映射系统与基于光纤的电光（EO）探头的微波，天线特性。在该探头中，EO晶体通过准直透镜安装在光纤的尖端上。由于透镜通过减少耦合回光纤的光束的损失而允许晶体厚度变长，因此提高了灵敏度。由于EO探针的尖端由I-mm立方EO晶体组成，并且不含金属成分，因此对映射电场的干扰非常小。将光纤固定在薄玻璃管中，在大面积的长期测绘过程中提供稳定的灵敏度。制作的EO探头的动态范围大于45 dB，平坦的灵敏度从1.95到20 GHz，方向性与交叉轴灵敏度隔离大于30 dB。偶极天线的测量和计算近场的比较表明，EO探头和偶极天线之间的静态或电感耦合可忽略不计。使用组织等效体模评估比吸收率（SAR），我们证明了EO探头用于绘制具有振幅和相位信息的电场的潜力。EO探头可以检测到小于0.6 V/m的电场，相当于0.5 mW/kg的SAR。该值满足确定SAR的法规中定义的最低检测限。这一结果显示了光纤光电探针近场成像系统在实际应用中的潜力。
We have developed a near-field mapping system with a fiber-based electro-optic (EO) probe for microwave, antenna characterization. In this probe, an EO crystal is mounted on the tip of an optical fiber through a collimating lens. Since the lens allows the crystal thickness to be lengthened by reducing the loss of an optical beam coupling back to the optical fiber, sensitivity is improved. Because the tip of the EO probe consists of a I-mm-cubic EO crystal and contains no metallic components, there is very little disturbance of the mapped electric field. Fixing the optical fiber in a thin glass tube provides stable sensitivity during long-term mapping over a large area. The fabricated EO probe has a dynamic range larger than 45 dB, flat sensitivity from 1.95 to 20 GHz, and directivity with cross-axis sensitivity isolation greater than 30 dB. A comparison of the measured and calculated near fields of a dipole antenna showed negligible static or inductive coupling between the EO probe and the dipole antenna. Using a tissue-equivalent phantom to assess the specific absorption rate (SAR), we demonstrated the potential of the EO probe for mapping the electric field with information of amplitude and phase. The EO probe can detect an electric field of less than 0.6 V/m, which corresponds to a SAR of 0.5 mW/kg. This value satisfies the minimum detection limit defined in the regulations for determining SAR. This result shows the potential of the near-field mapping system with the fiber-based EO probe in practical applications.