薄板型介质材料复介电常数的无损测量

Non-destructive measurement of complex permittivity of dielectric slabs

采用带法兰结构的TE01n圆柱谐振腔,用无损检测的方法测量薄板型微波介质材料的复介电常数。利用轴向模式匹配法对谐振腔内的电磁场进行了求解,给出了相对介电常数和损耗角正切的计算公式,并利用矢量网络分析仪对几种常用微波介质材料进行了测量,其结果表明:该测量方法对相对介电常数的测量误差不超过1%,而对损耗角正切的测量误差不超过10%。该方法还具备一腔多模的测试能力,测量频率可调,可用于介质材料频率特性的测量。

Based on the traditional TE01, cylindrical cavity, a new resonator is proposed for non-destructive measurements of the complex permittivity of dielectric slabs. It consists of a large planar metal plate, a dielectric slab, and a cylindrical waveguide armed with a flange at one end and a tunable piston at another end. The dielectric slab is sandwiched between the metal plate and the flange. The rigorous mode matching method is employed for analyzing the electric fields in the cavity. Expressions relating the complex permittivity with the eavity＇s physical dimensions and the measured Sn parameter are developed. Thereafter, several di electric slabs are tested to demonstrate the usefulness of this proposed method. It is found that by using this cavity, the measure ment uncertainty for the relative permittivity is within 1%, while the measurement uncertainty for the dielectric loss could not ex ceed 10%. This cavity has the advantage of measuring the complex permittivity at multiple resonant modes. Therefore, it could be used as a robust approach for characterizing the frequency dependence of the complex permittivity of dielectric slabs.