平板介质的微波分裂腔法介电常数测试技术

Permittivity measurement technology of flat dielectrics using microwave split-cavity method

摘要:

为实现微波频段平板类介质材料的介电常数的无损测试，研究了分裂式圆柱形谐振腔测试方法。介绍了分裂式圆柱形谐振腔的电磁场分析理论，采用模式匹配技术实现了介质加载条件下腔内电磁场分布的精确求解，得到了腔体谐振频率与材料介电常数之间的准确关系。在理论分析的基础上，制作了空腔谐振频率为10 GHz的分裂式谐振腔，并与前期研制的闭式谐振腔进行对比测试，介电常数实部测量结果相对误差小于1%。与国外同类产品进行对比测试，介电常数实部结果基本一致，损耗角正切测量结果更接近于文献参考值。因此，微波分裂腔法能够实现平板介质板材的无损测量，具有准确度高，使用方便等突出优势，可在微波频段内实现介电常数为 1~20，损耗角正切为1×10^-3~1×10^-5，板材厚度为0.1~2.0 mm的各类平板介质材料介电常数的准确测试。

Abstract:

The test method of split cylindrical resonator is studied in order to realize the nondestructive test of dielectric constant of flat dielectric materials in microwave band. The electromagnetic field analysis theory of split cylindrical resonator is introduced, and the accurate solution of electromagnetic field distribution in the cavity under dielectric loading is realized by using mode matching technology. The exact relationship between the resonant frequency of the cavity and the dielectric constant of the material is obtained. On the basis of theoretical analysis, a split resonator with cavity resonant frequency of 10 GHz is fabricated and compared with the previously developed closed resonator. The relative error of the measurement results of the real part of dielectric constant is less than 1%. Compared with similar foreign products, the real results of dielectric constant are basically consistent, and the measurement result of loss tangent of this device is closer to the reference value. Therefore, the microwave split cavity method can realize the nondestructive measurement of flat dielectric plates, with outstanding advantages such as high accuracy and convenient use. It can accurately test the dielectric constants of various flat dielectric materials with dielectric constant range of 1~20, tangent of loss angle 1×10^-3~1×10^-5 and plate thickness of 0.1~2.0 mm in the microwave frequency band.