Research On The Low Temperature Measurement Of Dielectric Parameters By Quasi Optical Cavity Method

With the rapid development of microwave and millimeter wave technology,dielectric materials are widely used,the measurement of the dielectric parameters of the dielectric material is becoming more and more important.The dielectric parameters of the dielectric material are closely related to the frequency and temperature.Under different operating frequencies and working conditions,the material will exhibit different electromagnetic properties.As the frequencies of the electronic devices are increased higher and higher and application environment are getting worse and worse,sometimes below zero or a few degrees below zero,so it is becoming more and more important to establish a set of test system for the dielectric parameters at millimeter band under low temperature environment.Firstly,the thesis introduces the progress of temperature measurement technology of dielectric parameters in China and abroad.By comparing the advantages and disadvantages of different test methods,the quasi-optical cavity method is used as the test method.Secondly,the paper analyzes the optical field and energy distribution of the optical resonator through MATLAB,and introduces the test principle of the dielectric parameters of the material.Based on the theoretical analysis,the quasi-optical resonator is designed which can be used in the frequency bands of 3mm and 8mm at the same time.The material is tested under vacuum and non-vacuum condition through the built system,and the influence of temperature and frost degree on the performance of the cavity is analyzed by data.In order to eliminate the effects of temperature and degree,the structure of the cavity is improved and the sealing device and the test fixture are developed.At the same time,in order to facilitate the connection with the external device,a coupling device with the quasi-optical cavity is designed.In this paper,semiconductor refrigeration dehumidification is chosen as the dehumidification scheme,and the corresponding dehumidification device is developed by comparing the advantages and disadvantages of different dehumidification techniques.In order to real-time testing,the paper developed a heating and temperature control device.Finally,each subsystem of the test has been tested,and the paper build a quasioptical resonant cavity temperature test system which can be worked in-50 ~ 100 ?,the test process has been determined and the test software has been prepared by VC ++.The standard test samples were tested by the developed temperature test system,and the test results were analyzed by error.The test results show that the temperature measurement system developed in this paper has good stability and practicability,and the dielectric parameters of low loss materials can be accurately tested.For high-loss materials,the dielectric parameters of the material can only be accurately tested at several frequencies.