Large-size Sample Permittivity Test System Applications

The main purpose of this dissertation is to measure the permittivity of big size samples. The material used for road constructing is the mixture of asphalt and rocks, so the big scale sample can represent the material's dielectric property accurately.After the research and analysis of several present permittivity measuring method, as the cavity perturbation method and free-space method can measure large-quantity sample more easily, we choose the two methods in this dissertation. Based on the dispersion characteristics of normal materials, we use the measuring result on 0.915GHz to represent normal material's dielectric on 2.45GHz, forerunner's measuring result of many normal materials can support this practice, the experiment in this dissertation can also prove this method practicable.In this dissertation I design the free-space dot-frequency permittivity measuring system, the calculating and designing work of the metal-lens and three-probe impedance measuring apparatus has been done. After software simulating, the sample's influence on permittivity measurement error has been researched, and the advice of choosing measure-sample has been given. In the process of permittivity cavity perturbation measurement, I found the suitable size of coupling-hole used in resonant cavity; a data processing method based on interpolation used in measuring Q-quantity has been given, after the measurement of plexiglass sample has been done, the measurement system has been proved to be accurate; after the permittivity measurement of big size asphalt mixture, the dielectric property varying caused by temperature change has been found. A data-correcting technique based on software simulating has been given to enhance the accuracy of measurement of samples which don't conform to measuring condition.