Study Of Micro-doppler For ISAR

Except for the movement of main body,the imaging targets of inverse synthetic aperture radar(ISAR)usually exist some inner-motion parts,such as the rotor blades of a flighting helicopter,the wheels of a moving vehicle,the coning motion of warhead of ballistic missile,the swing motion of hands or feet while pedestrians walk or run,and so on.These movements are named as micro-motion.Micro-motion generates additional Doppler frequency,which is named as micro-Doppler(m-D)effect.Different targets have specific the micro-motion characteristic,which provides a new method for radar target recognition and classification.This dissertation focus on the research of the m-D effect for ISAR imaging,including the removal of the m-D effect,three dimensional micro-motion trajectory reconstruction of space target by three-antenna interferometric radar,study of m-D signatures of a pedestrian,and body gesture recognition based on polarimetric m-D and using deep convolutional neural network(DCNN).The major contributions and innovations of this dissertation are summarized as follows:1.Study on m-D effect removal for ISAR imaging.We proposed a bivariate variational mode decomposition(BVMD)method which can reserve the main body of target and remove the micro-motion part of target.The variational mode decomposition(VMD)method is extended to complex values,and the BVMD method was proposed.The BVMD method decomposes the radar echoes of range cells into a series of complex-valued mode functions according to which the echo signals of the main body and the micro-motion part can be separated by setting reasonable energy threshold.A refined ISAR imaging of removing micro-motion interference can be produced using conventional range-Doppler imaging algorithms.Both simulated and real measured data are processed to show the effectiveness of the proposed method.Furthermore,considering the aliasing phenomenon under low pulse repetition rate(PRF),VMD method is applied to micro-motion part of time-frequency(TF)spectrogram,and the period can be extracted effectively.2.Study on three dimensional micro-motion trajectory reconstruction of space target.A radar system of single transmitting and single receiving can only obtain the information of targets on the radar line of sight(LOS),and the three dimensional motion trajectory can not be extracted.We proposed a method for retrieving the three dimensional micro-motion trajectory of space target based on the interferometric phases obtained by using a wideband interferometric radar system with three antennas positioned in L-shape.The echo signals received by three antennas are decomposed based on Viterbi algorithm and intrinsic chirp component decomposition(ICCD)method,and the interferometric phases of different scatterers are respectively obtained.According to the extracted interferometric phases,three dimensional micro-motion parameters can be estimated and three dimensional micro-motion trajectory can be reconstructed.Simulation results demonstrate the effectiveness of the proposed method.Dual-antenna interferometric experiment has been carried out,and two dimensional micro-motion parameters have been estimated and two dimensional micro-motion trajectories have been reconstructed.The effectiveness of the proposed method was also verified via experimental result.3.Study on polarimetric micro-Doppler signature(MDS)of pedestrian.We carried out both simulation and experiment for pedestrain by using a Ka-band dual-polarization radar.In the simulation,the motion-captured dataset developed by Carnegie Mellon University motion graphic laboratory was used and the position information of a pedestrian can be obtained.FEKO and MATLAB are used to calculate the radar scattering of pedestrian'arms,based on which,HH and HV polarimetric MDS are analysed.Simulation results clearly show that in the TF diagram,HH m-D of arms is rising,while HV m-D is falling,which is verified by practical Ka-band radar experimental on a pedestrian.Our work show that by using polarimetric radar the MDS of human motion can be much well detected and identified which can be further explored for classification of different people.4.Study on body gesture recognition via using polarization radar system.Experimental data sets were recorded based on a Ka-band dual-polarization radar system under different angles and distances,and the echo signals of four body gestures have been acquired.The TF spectrograms can be obtained by short-time Fourier transform,from which we can see that different body gestures have different pplarimetric MDSs.We propose to classify four body gestures using the DCNN method via combining HH and HV polarization TF spectrograms.Compared with only using single HH polarization TF spectrogram or single HV polarization TF spectrogram,the recognition results show that a higher recognition rate can be achieved via combining HH and HV polarization TF spectrograms.