Study Of Microwave Dielectric Measurement Method And Its Application

The microwave detection relys on the received electromagnetic wave echo signal.It judges and obtains the required information according to the received echo signal.The dielectric constant is the most important parameter to characterize the intrinsic characteristics of the ground media,the value of the parameters to echo signal entirely depends on the dielectric constant.It is significant to study the method to detect dielectric constant using microwave technology.Based on the relevant theoretical knowledge,the paper separately designs the measurement systems of these 3 dielectric constant measurement methods,including the waveguide method,free space method and radar detection method.Furthermore,the measurement principle and applicable conditions are introduced in detail.Firstly,the structure and algorithm are improved on the basis of the traditional waveguide method.The waveguide method has the characteristics of high measurement accuracy and simple calculation method.It's particularly suitable for the measurement of the dielectric constant of low-loss dielectrics.The design introduced in my paper covers a series of approaches to improve the measurement accuracy,including the calibration of non-standard parts,the correction of positioning error and the addition of standard organic glass material boxes,etc.According to the calibration process,the corresponding algorithm derivation is implemented,the hardware system equipment is set up,and finally the entire measurement system is improved.What's more,the feasibility of the improved method is verified experimentally.Secondly,based on the measurement principle and applicable conditions of free space method,my paper introduce a design of simple system which is suitable for field measurement including isolator,three-probe-impedance and lens antenna,the measurement principle is also recommended.Lastly,I focus on the radar detection method to the dielectric constant,and use oko-2 radar and 2.0G air-coupled antennas to build a detection system.In outdoor environment,the highway subgrade is used as detection object,and through the processes such as data acquisition,data process and interpretation,the relative dielectric constant of the surface layer material is measured according to the dielectric characteristics of each structural layer of the subgrade.Moreover,the thickness of the subgrade surface is further calculated.The data information acquired by the radar detection system is imported into the Reflex software,and the data is subjected to a series of process,such as static correction,filtering,and gain.Finally,the required parameters are obtained through data interpretation,and the relative dielectric constant of the subgrade material can be obtained through calculation.Based on the dielectric constant of the surface layer material,the thickness of the subgrade layer is further calculated by calculating the propagation velocity of the electromagnetic wave in the surface layer medium.The time profile displayed by Reflex can visually present the variation trend of the thickness of the subgrade surface and the specific thickness measurement.In my opinion,this application is of great significance for road safety inspection.