Research Of Ultra-high Temperature Meashrement Technique For Complex Permittivity Of Materials

Microwave materials are widely used in many fields such as military, aerospace, communications, electromagnetic properties of microwave materials are directly related to the designed electronic device and system performance. The microwave material not just works at room temperature environment, even more works at high or ultra-high temperature environment. Especially for radomes on high-speed flight missiles, rockets and other aircrafts. Due to aerodynamic heating between the aircraft and the atmosphere, the radome’s temperature will increase to thousands of degrees. Since the dielectric properties of microwave dielectric material will change with the variation of temperature, the change of antenna aperture working environment temperature will have a serious impact on the aircrafts’ proper functioning of communications, guidance and other electronic devices. During the development, production, and applications of microwave materials, it is necessary to master the variation of dielectric properties at different temperatures and operating frequency. Therefore, building an ultra-high temperature system, which can effectively test the dielectric properties of microwave materials precisely, has an extremely important strategic significance and practical value.Based on the electromagnetic parameters testing technical indicators and methods of microwave materials, short-circuited line method is selected to accomplish testing research of dielectric properties of microwave material at ultra-high temperature in this article. In order to improve the precision of the testing system, improvement and innovation on the core components of traditional testing system can be found in the following two aspects: First, using the large reflective sheet waveguide to calibrate is proposed innovatively, which improves testing accuracy of the system; Second, by opening the short circuit board, the sample can be in close contact with the short circuit board, which improves testing accuracy and is convenient for taking and putting the samples. Both of these two method have been applied for a patent for invention. Meanwhile, rectangular-coaxial mode conversion connector and high performance high temperature testing waveguide components for testing subsystem are designed and fabricated. Moreover, taking the subsystems as the core, by combining the solid state induction heating, vacuum cavity, water cooling, automatic temperature control and other subsystems scientifically and system debugging, the testing system is built. Ultra-high-temperature testing of dielectric properties of microwave materials at a temperature of 1800 ℃is realized by using automatic testing software developed by ourselves.The technical indicators of the test system are as follows:Test temperature: Room temperature ~ 1800℃Test frequency: X Band(dot frequency)Test range:Room temperature: ε_r’ = 1.0 ~ 10 tanδ_ε = 0.001 ~ 1.01800℃: ε_r’= 1.0 ~ 10 tanδ_ε = 0.05 ~ 1.0Test errors:Room temperature:|Δε_r’/ε_r’|≤3.0%，|Δtanδ_ε|≤18%tanδ_ε+0.0031800℃:|Δε_r’/ε_r’|≤6.0%,|Δtanδ_ε|≤ 25% tanδ_ε+ 0.01...