A practical method for measuring the complex relative permittivity of epoxy resins and other viscous liquids over a wide temperature range in S-band is presented. The method involves inserting a hot glass tube, filled with the liquid-under-test (LUT), into a length of WR-340 rectangular waveguide connected between two ports of a Vector Network Analyzer, which measures the reflection and transmission coefficients at 2.45 GHz. The heating arrangement consists of a temperature-controlled glycol bath, where the LUT-filled glass tube is placed. The dielectric properties are determined using an optimization routine, which minimizes the error between the theoretical and measured scattering coefficient data. The theoretical values of the scattering coefficient data are computed with the help of a numerical 3-D electromagnetic field simulator, the CST Microwave Studio. The dielectric properties of the empty glass tube (required by the simulation code) are also measured using the above methodology.

中文翻译：

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测量环氧树脂随温度变化的介电特性的无损方法

提出了一种在 S 波段的较宽温度范围内测量环氧树脂和其他粘性液体的复相对介电常数的实用方法。该方法包括将装有待测液体 (LUT) 的热玻璃管插入连接在矢量网络分析仪两个端口之间的 WR-340 矩形波导中，该分析仪测量 2.45 GHz 下的反射和传输系数. 加热装置包括一个温控乙二醇浴，其中放置了填充 LUT 的玻璃管。介电特性是使用优化程序确定的，该程序将理论散射系数数据与实测散射系数数据之间的误差降至最低。散射系数数据的理论值是在数值 3-D 电磁场模拟器的帮助下计算的，CST 微波工作室。空玻璃管的介电特性（模拟代码需要）也使用上述方法测量。