Research On Target Detection And Parameter Estimation Of UAV Based On Micro-doppler Signatures

In recent years,the detection and parameter estimation of radar targets by using the micro-doppler effect generated by the micro-motion of radar targets has attracted widely attention in the radar field.The micro-doppler effect generated by the micro-motion of target can reflect a lot of information about the target’ s motion state,size and shape,and this feature is "unique",which provides an effective way for the feature extraction and parameter estimation of radar target.In this paper,the unique micro-doppler effect generated by the high-speed rotation of rotor blades in the flight process of unmanned aerial vehicle(UAV)target is utilized to realize the research on the method of UAV target detection and parameter estimation.In addition,the ku-band linear frequency modulation continuous wave(LFMCW)radar system is used to collect the field experimental data of the small UAV,processing the measured data and extracting the microdoppler characteristics,and compare with the results of theoretical simulation.Firstly,the modulation effect of target micro-motion on radar echo and the principle of generating micro-doppler effect are analyzed.On the basis of rigid body’s motion model,the motion model of multi-rotor UAV is established,the mathematical expression of UAV target echo of LFMCW radar is deduced,the signal processing method of LFMCW is studied,and the micro-doppler characteristic of rotor is analyzed.Then,the Constant False Alarm Rate(CFAR)detection method based on LFMCW radar is studied.CFAR detection is performed on the echo spectrum of distance domain and doppler domain respectively.In order to reduce the influence of clutter,moving target indication(MTI)detection method based on LFMCW radar is studied.Finally,the method of micro-doppler feature extraction and parameter estimation of multi-rotor UAV target is studied by using the joint time-frequency analysis technology.The time spectrum of target echo is analyzed to estimate the parameters.In view of the weakness of the joint time-frequency method,which requires high micro-doppler intensity and signalto-noise ratio,a set of empirical mode decomposition method for radar echo signal of UAV has been studied.By analyzing the intrinsic mode functions(IMFs)decomposed after empirical mode decomposition(EMD)of radar echo,the relationship between the speed and number of blades of UAV and the number of flicker in the IMFs component has been found.In the case of spectrum aliasing caused by excessive frequency modulation period of radar,a parameter estimation method based on radar echo spectrum is proposed,by combining with EMD method,the further estimation of UAV’s parameters is realized.