Study Of Material Density Measurement Techniques Based On Microwave Coaxial Resonant Cavity

Density measurement technology is used widely in the basic research, such as metrology, application physics, oceanography, etc. and the application engineering, such as chemical industry, petrifaction, metallurgy, etc. The density measurement is one of basic methods to search material characteristic and product quality inspection by infrared measurement method, ultrasonic measurement method, and microwave measurement method, etc. The microwave measurement method has characteristics of strong anti-jamming ability, high precision, good reliability of the measurement result, realizing quick and on time measurement, safety to handle and low application cost which is great decreased by product cost falling. Therefore, the microwave measurement method will have wide application foreground. The core component of the microwave measurement device is microwave sensor which was designed by practicality measurement in the past. The practicality measurement had much research cost and long research period. Using emulational measurement instead of practicality mensurement can greatly lower the research cost and short the research period with the development of computer emulational measurement which is used as assistant design method on the design of the microwave component.The paper is devided into two parts to illustrate. The first part is to design a microwave coaxial resonant cavity which has good electromagnetism characteristic with HFSS emulational softwave. To achieve the purpose, we use dimension calculation formula of coaxial resonant cavity to gain original dimension. Then, main design paraments of the coaxial resonant cavity, such as coupling mode, the location of coupling ring in the ring coupling mode and the thickness of protect cover, are emulated by HFSS to receive a reasonable dimension of the coaxial resonant cavity. After that, the length of the coaxial resonant cavity is adjusted to elevate resonant frequency and the coaxial resonant cavity is obtained which has good electromagnetism characteristic. The second part is to measure material density using the received coaxial resonant cavity with HFSS. The emulation uses dryness tobacco leaf as measurement material. Firstly, the connection between dielectric constant and density of the material using diffenent dielectric constant and density which are gained by changing the aquiferous ratio of the tobacco leaf. Then, the function connection between the dielectric constant and the frequency of the coaxial resonant cavity is gained. The coaxial resonant cavity used in the emulation is gained in the first part. Finally, the equation of the aquiferous tobacco leaf density using the coaxial resonant cavity is achieved.The paper gives relatively design parameters of the coaxial resonant cavity to measure and particular measurement is gained by using certain material which has reference meaning on the using of coaxial resonant cavity to measure material density in practice application.