Measurement And Research Of The Dielectric Constant For Materials At Different Wavebands

Dielectric constant is one of the important physical properties of materials.With the wide application of various dielectric materials,the measurement of the dielectric constant for different materials is particularly important.Based on relevant theoretical knowledge,two methods for measuring the dielectric constant of materials at different wavebands are studied in this thesis.(1)At the low frequency band,the dielectric constant of the material is measured based on the microstrip line measurement device.The equivalent dielectric constant of the microstrip line covered by the material to be measured is first calculated by the transmission line theory,and then the actual dielectric constant is obtained by the variational method.After that,the model is established in the simulation software,and the inversion calculation is used to verify the correctness of the theoretical derivation.The simulation frequency is 0-0.5 GHz.The final simulation results are basically consistent with the material values,verifying the validity of the theory.On the basis of theoretical derivation and simulation calculations,the physical prototypes were processed and experiments were conducted.Several different materials were measured.The results were basically consistent with the labeled values of the materials,and the error did not exceed 8%.The experimental results show that the device can effectively measure the dielectric constant of the materials.The measuring device has certain flexibility,simple operation,and is inexpensive.(2)At the high-frequency terahertz band,a method based on terahertz time-domain spectroscopy is used to measure the dielectric constant of the materials.Terahertz timedomain spectroscopy is a free-space measurement method with two different measurement ways,i.e.,reflection and transmission.In this thesis,the two measurement methods are theoretically deduced,and then the model is established in the simulation software and the simulation inversion is carried out to verify the feasibility and effectiveness of the theoretical deduction.On the basis of theory and simulation inversion,dielectric constants of several different materials were measured by the transmission method,and the experimental error rate was less than 6%,indicating that the method based on terahertz time-domain spectroscopy can effectively measure the dielectric constant of materials.The two methods working at different frequency bands,can effectively measure the dielectric constant of the materials,and the error is relatively low.It indicates that the measurement methods studied in this thesis are accurate and feasible,and have certain reference significance in the measurement of the dielectric constant of the materials.