Cylindrical Cavity Of The Dielectric Parameters Of Low-power Media Measurement Method

The complex permittivity measurement of low-loss materials using a cylindrical cavity is researched in this paper. Based on the technique, a set of automatic system at X band is built. This system controls the vector network analyzer by a computer, measures the cylindrical cavity with sweeping frequency method. According to the frequency and the quality factor of the cylindrical cavity unloaded and loaded, thesystem can calculate the permittivity ε'_r and the loss angle tangent tan 8 of thematerials being tested. In this paper, the distributing of electromagnetic field and basic parameters of thecylindrical cavity are analyzed, based on this, the process of designing the TE_01p modecylindrical cavity is described in detail. In order to avoid disturbing modes, the cylindrical cavity is inspired with signals of reverse phases and is made with somenotches on the inside surface. The formulas of calculating the permittivity ε'_r and theloss angle tangent tan δ are figured out. At last, a set of automatic system at X band is built. The way of using the system and the process of measurement are given. The system is easy to operate and works at high speed. The results of some low-loss materials tested under this system show that the system works at high accuracy and it can satisfy the requirements of project.This paper provides a set of good way to solve the complex permittivity measurement of low-loss materials.