基于多路开口同轴探头的介电常数测试系统开发

本文提出并开发了一种基于多路开口同轴探头的介电常数测试系统，利用射频多路开关实现多探头分时工作，获取多路反射系数并对其进行补偿，基于准静态模型反演得到介电常数，首次利用开口同轴探头法实现了介电常数的空间多点测量；然后通过测量已知介电常数的液体，对照液体介电常数理论值进行误差分析，验证了该系统的准确性；最后使用该系统对非均匀含水石英砂进行测量，获得了空间多点的介电常数分布，进一步结合介电混合定律反演得到了空间多点石英砂中水体积分数。结果显示：该系统获得的介电常数反演值与理论值吻合度高，误差分析表明该系统精度优于现有主流的单探头商业测试系统，利用该测试系统可实现对非均匀介质介电常数空间多点分布的精确测量，且测量精度高、可靠性好，扩展了开口同轴探头法在非均匀介质测量中的适用范围，对非均匀介质的微波介电特性研究具有重要科学及工程意义。

Development of Permittivity Test System with Multi-Channel Based on Open-Ended Coaxial Probe

In this paper, a test system with multi-channel based on open-ended coaxial probe was proposed. The time-dividing operation of the multi-probe was realized by setting a RF multi-way switcher, meanwhile reflection coefficients were compensated, and the permittivity was inversed with quasi-static model. This is the first time to achieve dielectric measurement at multi-point with open-ended coaxial probe. In order to verify the reliability of this test system, several liquids with known permittivity and medium with homogeneous permittivity were measured. Finial, special dielectric distribution information of inhomogeneous sand containing water was obtained by using this system, and water saturation was reversed with dielectric mixing law. Experimental results show that permittivity obtained by the test system match theoretical data precisely. Results from error analysis present that the precision of the system is better than the existing mainstream commercial single probe test system, and it can be used to measure the permittivity of inhomogeneous media accurately. The proposed test system with high precision and reliability expands the application of open-ended coaxial probe method in permittivity measurement of inhomogeneous samples, and it is scientifically and engineeringly significant to dielectric properties study of inhomogeneous media.