Research Of Variable Temperature Measurement Technique For Complex Permittivity Of Dielectric Materials By Free Space Short-circuited Line Method

With various of electromagnetic products be used in people's lives and work,microwave materials,which are important carriers of electromagnetic wave propagation,have been widely used in all industries.For example:Aerospace,wireless communications,industrial production,medical education,etc.The electromagnetic parameters of microwave materials vary with the frequency and environment,so it is especially important to test the electromagnetic parameters of microwave materials,especially the electromagnetic parameters at high temperatures.At present,China and other countries'research methods on the electromagnetic parameters of microwave materials have been conducted in-depth research,and have get great results,but many test methods are limited to normal temperature testing,the accuracy of high-temperature testing is not accurate.This subject uses the free space terminal short-circuit method to test the material at room temperature and high temperature.It is relatively simple in theory and the test fixture is easy to make and does not directly contact or destroy the material.It has low requirements for the accuracy of the material production,and it has many big advantages compared with other test methods.This article introduced a variety of electromagnetic parameters testing methods and their research background at China and abroad.Then compared several common test methods and chose to use the terminal short circuit method for testing.Then the test principle of the terminal short-circuit method was analyzed,and the traditional test model was improved:the metal ellipsoid reflector was used instead of the dielectric lens to focus the antenna,and the original linear structure was changed to an L-shaped structure,which reduced the fixture,saved the space and Improved focusing performance.In this paper,the ellipsoidal reflector,14GHz-16GHz feed antenna and metal short circuit board are designed,and the whole system is verified by simulation.Then the calibration model and method of single-port test system are introduced.The influence of multipath effect on the test in free space is analyzed and the method of weakening multipath effect is given.Then set up two sets of test systems at room temperature and high temperature,and give detailed test procedures for the corresponding two systems,and tested some microwave materials.Finally,according to the test results,the deficiencies and improvement methods of the test system designed in this paper are analyzed.The testing index:Frequency:14GHz?16GHzTeste temperature:Room temperature?1000?Test range:Room temperature:1??_r?10,0.001?tan ??0.51000?:1??_r?10,0.005?tan ??0.5Test errors:Room temperature:|??_r~?/?_r|?5.0%,|?tan ?/tan ?|?20%tan ?_?+0.0051000?:|??_r~?/?_r|?10.0%,|?tan ?/tan ??20%tan ?_?+0.005...