The Measurement Method Of Complex Dielectric Constant In VHP Band

Complex permittivity is an important physical property of dielectric materials,and it has important theoretical and practical significance for the study of dielectric constant.How to conveniently and accurately measure the dielectric constant of a material plays an important role in biomedical,microwave electronic technology,and geological exploration.This paper mainly studies the testing method of complex permittivity in VHF band of dielectric materials,focusing on the analysis of coaxial transmission/reflection method,and proposes an improved coaxial cavity test structure based on this method.Firstly,the approximate size of the coaxial air line was analyzed using three-dimensional electromagnetic simulation software,and a PTFE-filled coaxial cavity model was constructed.Based on this model,a correction algorithm based on the medium to be measured was given.Finally,the actual parameters of the PTFE with different dielectric parameters were measured.The corresponding relationship between the S parameters and the dielectric constant of the proposed structure was used to obtain the complex permittivity of the sample to be measured and compared with the nominal value.This verified that the coaxial cavity test structure has good accuracy and reliability.