Research On Echo Separation Method Of Target With Micro-motion Part In Inverse Synthetic Aperture Radar

Inverse synthetic aperture radar can image a rigid body whose scattered points have the same motion state,but under normal circumstances,in addition to the motion of the main body,there will be some micro-movements that are different from the motion of the main body.These micro-movements modulate the radar echo,thereby producing micro-Doppler effect.The micro-Doppler effect is a “double-edged sword”.For the imaging of the main body of the target,it is unfavorable.If the micro-Doppler effect is very serious,it will interfere with or even directly submerge the image of the main body of the target,thereby affecting the imaging effect.However,it is advantageous to target recognition and classification.The micro-Doppler signal in the radar echo can be used to obtain the information of the micro-moving parts of the target,which is conducive to target detection.Therefore,separating the signal of rigid body and the micro-Doppler signal in the radar echo can take into account both the main body of the target and the micro-moving part.The main target to research in this paper is the target with rotating parts,especially the propeller aircraft.This paper analyzes the radar echo signal model of the target with rotating parts,and draws the conclusion that the echo signal modulated by the rotating micro-movement is a time-varying non-stationary signal.Two timefrequency analysis tools,short-time Fourier transform and Wigner-Ville distribution,are introduced,and short-time Fourier transform is selected as the tool for subsequent analysis.The propeller blades of the propeller aircraft are modeled and the echo signal is derived.Based on the echo signal,the method of estimating the rotational angular velocity,the number of blades and the length of the propeller blades is introduced.A simulation experiment is carried out on the propeller blade,and the estimation of its structure and motion parameters is realized.This paper mainly realizes the separation of signal of rigid body and microDoppler signal from two aspects: parameter estimation and signal decomposition.When the main body of the target rotates at a uniform speed,the micro-Doppler signal of the rotating micro-moveing component is in the form of a sinusoidally frequency modulated signal.Based on this,the echo signal can be separated by estimating the parameters of the sinusoidally frequency modulated.In the method of parameter estimation,the inverse Radon transform and the discrete sinusoidally frequency modulated transform are mainly studied.Aiming at the shortcomings of the discrete sinusoidally frequency modulated transform,an improved artificial bee colony algorithm is used to optimize it.Through simulation experiments,the parameters of the sinusoidally frequency modulated signal are estimated,and the separated signal of rigid body is used to obtain the image of the main body of the target with the mitigation of micro-Doppler interference.Since the micro-Doppler signal is no longer in a strictly sinusoidal form when the main body of the target rotates at a uniform variable speed,the method of parameter estimation is no longer applicable,and the advantage of the method based on signal decomposition appears.In the method of signal decomposition,the complex-valued empirical mode decomposition and adaptive Chirplet decomposition are mainly studied,and aiming at the defects of the Chirplet decomposition,a short-time Chirplet decomposition method is proposed.Simulations and measured data experiments have obtained the image of the main body of the target without micro-Doppler interference.Imaging of micro-moving parts is also a place to pay attention.In this paper,methods of high-speed rotating target imaging based on particle swarm optimization algorithm and inverse Radon transform are studied.At the same time,the particle swarm optimization algorithm can also realize the separation of the signal of rigid body and the micro-Doppler signal in the range-slow time domain,which is conducive to the subsequent imaging of the main body of the target and the imaging of the micro-moving parts.The simulation experiments have obtained good imaging results of micro-moving parts.