Research On Ranging And Velocity Measurement Technology Of Linear Frequency Modulated Continuous Wave Radar

In recent years,millimeter-wave radar has been widely used in military and civilian fields due to its advantages of small size,low cost,light weight,high resolution,and strong penetration.Based on the background of Linear Frequency Modulated Continuous Wave(LFMCW),this thesis focuses on the two main problems of LFMCW radar ranging and speed measurement,speed ambiguity problem and frequency modulation nonlinear(FMN)correction problem.In practical application scenarios,high-speed moving targets will appear speed blur phenomenon,so the thsis studied the velocity defuzzification(VD)method to improve the accuracy of speed measurement.The actual millimeter radar system is affected by the non-ideality of the device and the stray and noise of the system,there will be a nonlinear problem of frequency modulation.Therefore,the thsis studied a nonlinear correction method to improve the ranging accuracy.The main research contents and work of this thesis are as follows:1.The thsis studied the VD method of millimeter wave radar.In view of the high time complexity of the existing velocity ambiguity resolution algorithm and the long scanning time of radar,The thsis proposed a VD method based on constant frequency assistance.Firstly,the combined waveform of constant frequency band and sawtooth band is used to avoid transmitting repetitive frequency pulses and improve the time utilization.Then,the real speed of targets in constant frequency band is estimated by fast Fourier transform(FFT).Finally,the discrete Fourier transform(DFT)rotation factor is constructed by using the real speed estimated in the constant frequency band to match the speed of the target in the sawtooth segment without additional multi-target matching operations,which improves the target matching performance.This method has the advantages of high speed measurement accuracy and simple algorithm.2.Studied the parameter estimation and one-dimensional range profile correction algorithms for LFMCW radar frequency modulation nonlinearity,Aiming at the error transmission problem of traditional nonlinear phase error parameter estimation methods,proposed an improved high order ambiguity function(HAF)estimation method.Firstly,FFT is used to roughly estimate the spectrum of high order instantaneous momentum(HIM).Then the Chirp-Z transform(CZT)is used to estimate the spectrum,which effectively reduces the impact of error transmission and improves the performance of parameter estimation.Finally,Aiming at the high time complexity of the existing correction algorithms,a cross-correlation correction algorithm based on signal processing is proposed,which not only ensures the correction performance,but also reduces the complexity of the algorithm.3.Relying on the chirp millimeter-wave radar platform of the research group,the thsis carried out the actual application of ranging and speed measurement.Firstly,introduced respectively the composition of the radar system,the selection principle of main parameters,the process of RF front-end processing and the design process of signal processing.Then,according to the functional requirements of the system software,designed and implemented the radar signal processing algorithm software platform and the radar embedded software architecture,and introduced the overall system design scheme.Engineering practice shows that the software can stably call algorithms of different functions in sequence according to the algorithm flow table in the designed embedded software architecture.Finally,using the realized software platform,the thsis collected the measured data and the verified the function of ranging and speed measurement.