Research On Microwave Radar Level Measurement Technology

High-precision radar level meter has been playing a very important role in industrial production,with the arrival of "13th Five-Year" plan and industry 4.0,China's level instrumentation industry demand is rising rapidly,the traditional pressure level meter,ultrasonic level gauge,guided wave level gauge and laser range finder has the limitations of measurement accuracy or application range,it is difficult to meet the actual needs of industrial measurement.Therefore,this subject mainly studies a miniaturized,non-contact,high precision of linear FMCW radar level measurement system.This paper first analyzed the basic principle of linear FMCW radar measurement and the mathematical model of the beat signal,and then designed a radar level measurement system solution based on Infineon 24 GHz radar transceiver BGT24MTR11 as system front-end core and ARM controller STM32F4 as system baseband control processing part.Radar signal transmission and reception using microstrip antenna to achieve front-end module miniaturization design,microstrip antenna gain and half-power beam angle directly determine the measurement range of the system,so this article through the HFSS simulation software to optimized the antenna parameters to achieve the best performance indicators.Then,this paper analyzed the factors that affect the measurement accuracy of radar level gauge,including sweep bandwidth,VCO nonlinearity and digital signal processing frequency measurement error.The increase of sweep bandwidth can improve the measurement accuracy,but also lead to swept nonlinearity.The linearity and stability of VCO seriously affect the accuracy of the system distance measurement,so this paper designed the digital temperature compensation and nonuniform step correction methon to improve the sweep linearity and stability of the radar signal,and by using the method of synchronous signal to filter out the interference caused by frequency flyback.For the signal processing frequency measurement error,this paper used the method of linear frequency modulation z transform and spectral maximum estimation algorithm based on FFT technology to realized the fast and high precision measurement of the beat signal frequency.On the basis of the key technology research,the article designed the baseband hardware circuit with ARM controller as the core,including the modulation signal generation circuit,the pre-low noise amplifier circuit,the filter and program-controlled amplifier circuit,the signal acquisition circuit and so on,and use Keil software to achieve the overall architecture design and algorithm realization of the system software.Finally,the signal source is used to simulate the beat signal to test the function of each module of the baseband and verify the reliability of the software algorithm,and set up the experimental platform for the overall test and analysis of the experimental prototype.The experimental waveform and test data showed that the designed radar lever measurement system has good stability,but the measurement accuracy of the system needs further study and improvement.