On The Millimeter Wave Imaging Algorithm By Motion Compensation For Pedestrian Safety Check

In recent years,as the number of people's traveling increased,so does the pressure of safety check in public places,and it will be time-consuming if each passenger is checked in tra-ditional ways,so new safety checking technique is needed for quick passing pedestrians.Compared to the millimeter wave safety checking system for stationary targets,the millime-ter wave imaging system for moving targets is not yet mature,and there are some usage limitations of the existing imaging algorithms.Hence,in this paper,the millimeter wave safety checking system and imaging algorithm for stationary and moving targets are studied.The main work and contributions of the paper include:(1)De-aliasing imaging algorithm is proposed.For stationary imaging targets,in practice,antenna intervals are usually greater than half the wavelength of the transmitted millimeter wave,which causes the received echo signal spectrum to alias.To solve the problem of aliasing,the relationship between the mixed echo signal spectrum and the unstacked echo spectrum is analyzed in the paper,using two-dimensional sampling theorem,and the process of obtaining the target's reflection coefficient spectrum from the mixed spectrum is described as the process of solving a least squares problem.The imaging results on the simulation data and the virtual data show that,in the case of aliasing,the imaging quality of the de-aliasing algorithm is better than that of the directly used traditional algorithm,and close to the imag-ing quality of the traditional algorithm when there is no aliasing.The simulation results also show that the de-aliasing algorithm has fast imaging speed and strong anti-noise ability,con-sequently it is practically valuable.(2)An imaging algorithm for the target moving at a constant speed based on motion com-pensation is proposed.The dense array scans the imaging target for a longer period of time,during which the apparent target movement results in strong motion artifacts in the imaging results.In order to handle this problem,based on the hypothesis that the target is relatively stationary during each line of antenna's scanning,the relationship between the echo spec-trum of the target moving at a constant speed and the echo spectrum of the target keeping stationary is derived.Then an imaging algorithm based on motion compensation is proposed.Matlab simulation results show that the algorithm has clear imaging results.Moreover,the algorithm has no special requirements for the distance from the target to the antenna array,and hence has a wide extent of applications.(3)A blocking imaging algorithm for moving target based on positions of scatter points ob-tained by depth camera is proposed.Concerning about the long scanning time of the dense array,this paper also divides the dense array into several blocks with short scanning time,and assumes that the target is relatively static during antenna scanning in each block.There-fore,using the echo data of each block to respectively image,and then based on the target's location information recorded by the depth camera at the sampling time of each block,the final imaging results are synthesized,and a blocking imaging algorithm is obtained.Mat-lab simulation results show that the algorithm has clear imaging results and a low algorithm complexity.In addition,the algorithm also has no special requirements on the distance from the target to the antenna array,so it has a wide range of applications.