Research Of Measurement Method For Solution Concentration Based On Microwave Perturbation Technique

With the continuous development of microwave technology,microwave measurement technology has been widely used in society,technology and economy.The fields of microwave technology applications include military,industrial,medical,scientific research,precision detection,and communication systems.In the context of information technology,microwave technology plays a huge role in every technological change,such as the upgrade of communication networks,global positioning systems,wireless local area networks.The application and development of microwave has also become a hot topic in contemporary scientific research.Based on the material perturbation technique of perturbation theory,this paper constructs a microwave cavity sensor solution measurement system to detect different concentrations of glucose solution.The resonant frequency of the microwave cavity designed in this study is 7 GHz.And the working mode is TE₀₁₁ main mode.The simulation model is built by electromagnetic simulation software,in which the sensor size is simulated and optimized.And the specific size of the microwave cavity is determined.Based on the material perturbation technique,the mathematical model of the TE₀₁₁ mode cylindrical cavity sensor solution measurement is derived.The resonance frequency is linear with the solution concentration.The solution is placed in the resonant cavity by obtaining the amount of change in the resonant frequency.According to the results of previous theoretical research and simulation optimization,the TE₀₁₁ cylindrical cavity sensor is processed and fabricated,and the waveguide is coupled to the cavity through a small hole.Configure 70-150 mg/dl glucose solution,step by 10 mg/dl,put different concentration of glucose solution into the cavity solution tube,and record the corresponding resonance frequency through the network analyzer.The experimental results show that the experimental measurement accuracy is below KHz,and the glucose solution concentration is linear with the resonant frequency shift.The mathematical model of glucose solution is derived.The theoretically calculated frequency shift slope is 4460,and the experimentally measured frequency shift slope is 4515.The two are basically consistent,and the relative error is about 1.233%.This measurement method has high-precision detection performance.Theoretical mathematical models can be used for scientific prediction and guidance for subsequent experimental measurements.This paper designs a scheme for the automatic detection circuit of the cavity measurement.The automatic detecting circuit is used to test the resonant frequency,which is mainly composed of a low frequency circuit for judging whether the resonant cavity is resonant,the frequency source frequency adjustment direction,the frequency source is controlled,and the corresponding microwave device.The microwave device transmits the resonant cavity signal to the low frequency circuit,and the information obtained by the low frequency circuit is converted into a digital signal input to the FPGA,and the FPGA adjusts the automatic detection circuit according to the signal,thereby realizing the automatic detection of the resonant frequency of the microwave resonant cavity.