Relative dielectric constant measurement system for natural soil in microwave region

研制了一种用于测量天然土壤介电常数的开放式同轴探针及其数据处理方法。根据探头的几何形状，建立了探头的等效电路，推导了探头内介质的反射系数（测量值）、复介电常数等参数之间的关系。利用这些关系，计算了介质的相对介电常数。给出了不同含水量下介电常数实部和虚部的测量结果。在雷达遥感中，土壤含水量的测量是一个重要的问题，其中使用了雷达后向散射⇔介电常数⇔含水量的关系。介质介电常数与微波散射有直接关系，该探针和方法适用于液体介质。该研究有望扩大其在微波散射领域的应用。

An open-ended coaxial probe and its data processing method are developed for measuring the dielectric constant of natural soil. An equivalent circuit of the probe is built based on its geometry, and relations among the reflection coefficient(measurement), the complex dielectric constant of the medium filled in the probe and others are derived. Using the relations, a relative dielectric constant of the medium is calculated. Measurements of real and imaginary parts of the dielectric constant with different water contents are demonstrated. In radar remote sensing, measurement of soil water content is an important issue, where the relation, radar backscatter⇔dielectric constant⇔water content is utilized. The dielectric constant is directly related to microwave scattering, and furthermore this probe and method are applicable for liquid media. This research is expected to expand its use in the field of microwave scattering.