Research On The Technology Of Complex Permittivity Measurement With Free Space Resonator

With the development of science and technology, the technology that how to accurately measure the complex permittivity of microwave materials under different environment and different application has been playing an important role in our society.At present, there are a lot of methods to measure the complex permittivity of microwave materials, mainly including the resonance method and the network parameter method. In this paper, we use the method of free space resonator to measure the complex permittivity on non-destruction condition.First of all, this paper introduces the domestic and foreign methods about the progress of the complex permittivity of the material testing and introduces these methods briefly. Based on non-destruction testing, this article analyzes the advantages and disadvantages of the current method, and a new test method was proposed—free space resonance method. Secondly, for the new test method, this paper introduces basic principle firstly and analyzes the field distribution of the test system. According to the resonant condition of the resonance method, the article using the equivalent resonator method to obtain the basic principle and calculation formula of free space resonance.Thirdly, this paper designs the needed components for the system, including an X-band sport-focusing horn lens antenna an X-band coaxial-to-rectangular waveguide transition,an X-band circular-to-rectangular waveguide transition and coupling device. Finally, the test system was built with equipment already existing in the lab, the test software was written and the free space resonator test system was finished. Meanwhile, when the free space resonator system removes the coupling device, this system will become a single-reflection method test system, and it can be used to measure microwave complex dielectric constant of high-loss materials.This paper analyzes free space resonance with the same cavity length method and variable physical cavity method, and discusses complex dielectric constant test method of the two cases, to analyze of the test error by testing a variety of materials. Based on the works above, the free space resonance with good accuracy of complex permittivity test was finished.The testing index:Frequency: X-bandTesting range:?r: 1-10tan?:0.005-0.5Testing error:|??r/?r|?5.0%|?tan ??| ? 20% tan ??+0.002...