Research On Broadband Testing Technology For Dielectric Properties Of Low Loss Materials

With the rapid development and progress of economic society and science and technology,the performance requirements of materials are getting higher and higher in the fields of aerospace,television and radar.In the study of the dielectric properties of materials has also been more popular direction in the field of microwave materials.Clamping rod as a part of traveling wave tube,its axial dielectric properties also affect the performance of the holding rod.In this paper it is important to conduct testing of the dielectric properties of rod-shaped materials such as clamping rods.First of all,this article introduces the test methods commonly used in recent years,compared the application scope of each test method and their advantages and disadvantages.In this subject,in order to more convenient and accurate test,we choose cylindrical resonant cavity to test rod material dielectric constant.In theory,the distribution of electric field and magnetic field inside the resonator is analyzed,and the expression of resonant frequency and quality factor of the resonator is deduced.Based on the perturbation method and the exact field solution,the formulas of the dielectric constant and the loss tangent of the material to be tested are obtained according to the field structure in the cavity.Theoretical analysis and correction of cavity length changes caused by the cavity length,and the correction factor is taken into the dielectric properties of the formula,in order to reduce the impact of open-hole on the test results.In the meantime,the structure and distribution of the field in the case of incomplete filling of the dielectric material in the cavity are also theoretically analyzed.At the same time,the algorithm of material distribution test was deduced from the exact field solution method and the perturbation method,which provided theoretical support for the subsequent testing.Secondly,according to the requirements of the subject index,combined with the design principle of the cylindrical resonator,the size of the cylindrical resonator that meets the requirements of the index is designed and the slotting process is performed to suppress the interference of the interference mode.By the simulation software HFSS,the simulation was carried out,the cavity coupling structure was prepared,and finally the test cavity was debugged.In the test system,the mobile device has been improved over the traditional method,and each component of the mobile device has been developed.At the same time,an automatic control software has been programmed to control the motor for quick test.Finally,the aim of assembling and debugging the entire test system subcomponents is to ensure stable performance of each part of the test system.The test system is used to test several different standard samples in different positions.The test results are compared to show the uniformity of the axial complex permittivity of the samples.The test system also verifies that the following test indexes are satisfied:Test temperature:25?Test frequency:3-26GHzTest range:relative dielectric constant ?'_r:1¹1;loss tangent tan?:1×10^-65×10^3-Test error:???'_r/?'_r??3.0%??tan???8%×tan?+5×10^-6...