In this letter, a new microwave sensor of the coaxial resonant cavity with a single-open-ended circuit loaded capacitor is proposed and used to detect the liquids’ complex permittivity. The improved cavity has a higher internal electric field and smaller size when compared with the cylindrical cavity, which gives the sensor a high sensitivity in measuring liquids’ complex permittivity. A coaxial resonant cavity operating in 1.9 GHz was designed in this work. The silicone hose used for the test is inserted vertically from the center of the cavity, and the liquids under test (LUTs) are guaranteed to be 2 ml each time. The dielectric properties of LUTs will cause perturbation to the internal electric field of the cavity. By analyzing the measured data, the sensitivity of the cavity is 0.12%, and the relative errors of the real part of the measured value and the reference value are 3.67%. which shows the measured value has a good agreement with the reference value.

中文翻译：

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用于测量液体复介电常数的同轴谐振腔

在这封信中，提出了一种带有单端开路负载电容器的同轴谐振腔的新型微波传感器，并用于检测液体的复介电常数。与圆柱形腔相比，改进的腔具有更高的内部电场和更小的尺寸，这使得传感器在测量液体的复介电常数时具有更高的灵敏度。在这项工作中设计了一个工作在 1.9 GHz 的同轴谐振腔。用于测试的硅胶软管从腔体中心垂直插入，每次保证被测液体（LUT）为2毫升。LUT 的介电特性会对腔体的内部电场造成干扰。通过分析实测数据，腔体的灵敏度为0.12%，实测值与参考值的相对误差为3.67%。表明测量值与参考值吻合较好。