Research On The Key Technology Of Water Content Microwave Detection System

Many areas of fast, high-precision, non-contact, non-destructivematerials testing system urgently needs moisture, through research at homeand abroad microwave detection technology research status and key technologyin the material moisture detection, based on the dielectric properties of watermicrowave moisture content of materials detection system design and testingof key technologies to achieve studied, the topic has important theoreticalsignificance and application value, paper work is as follows:1. Based on microwave dielectric materials moisture detection needs andcharacteristics detection principle, a mathematical model was used to detectthe microwave transmission attenuation material moisture content, moisturecontent of the material discussed microwave and density independentattenuation and phase shift detection algorithm to analyze the rectangle TEwave resonator, TM wave resonance conditions, multi-harmonic and qualityfactor calculation, discussed the resonant cavity excitation coupling method.2. Based on microwave dielectric properties of the resonant structureselection and detection principle cavity perturbation method to study themedium column packing perturbation conditions and microwave resonant cavityperturbation method moisture content of materials detection algorithm model;perturbation method based on the dielectric constant of the resonator defectdetection model analysis, research and detailed derivation of the samedielectric cylinder shaped cavity perturbation system to improve themathematical model, solving the moisture content of the material expression.3. For the moisture content and density-independent detection of materialneeds, the study summarizes the double cavity parametric methods, materialdensity and pre-control law has nothing to do with the density of the sub-base operator assay principle, to study and propose a system based onconductive particles dispersed solid-liquid-gas-phase mixture of complexpermittivity of the mixture model based on volume, for the establishment of a function of the resonant frequency and the quality factor of the resonatormaterial with moisture and universality laid a theoretical foundation.4. Given the use of microwave resonant cavity opening to achieve thedensity-independent moisture content of materials online testing design,research and design phase locked loop microwave signal source, pulsedmicrowave frequency and power detection circuit, through experimental testson coaxial sensing properties of linear esonator material moisture detectionsystem simulation analysis, combined with experimental results discussedexcitation signal frequency selection, the protective cover of the mediamaterial selection, given the measured material prototyping, materialmoisture given obtaining standard curve.Finally, based on microwave material moisture detection system with asingle open-ended coaxial resonator, the paper gives the mathematical modelabout the water content of the material, the calibration curve, detection curve.The analysis on the detection results shows that, the system achieves highdetection accuracy, with error less than1%. It has good practicability, trulyrealize the online, real-time, high precision, and has practical function ofsingle end open coaxial resonator material external perturbation methodmoisture detection system.