Research On Passive Millimeter-wave Miniaturized And Standoff Imaging Techniques

As an advanced technique,Passive millimeter wave imaging system has essential applications in safety Inspection,fire detection and other detection fields.Millimeter wave can penetrate clothing to identify metal objects hidden between clothing and human body,so millimeter wave radiometer always utilized by security departments to detect dangerous hidden objects such as guns,ammunition,restricted knife and etc.,through a complex and messy environment.Compared with active millimeter-wave imaging technology,main advantage of passive millimeter-wave imaging technology shows in the process of using passive millimeter-wave imaging technology.Electromagnetic waves are not radiated to the human body,thereby avoiding any kind of affect to the human body.Especially the miniaturized station-open passive millimeter-wave imaging system can realize long-distance non-cooperative security inspection,which more effectively improves correlative efficiency and safety factor.This paper takes human security inspection as a discussion issue and designs a miniaturized standoff passive millimeter-wave imaging system.Then in the following parts of the dissection also studies the mechanism of passive millimeter-wave imaging system to detect hidden metal objects in human body.(1)As the theoretical basis of this paper,firstly,the principle of passive millimeter wave imaging is studied and analyzed.On this basis,the radiation characteristics of objects in 3mm band are analyzed.Theoretically,the influence of radiation characteristics of different materials on the resolution of passive millimeter wave imaging system is analyzed.(2)In the second part,according to the principle of quasi optical path design,considering the imaging distance,field of view and resolution of the system,the quasi optical credit system is designed with the design method of quasi optical path.The subsystem can concentrate the electromagnetic wave radiated by the target point on the receiving antenna,so as to improve the spatial resolution of near-field detection imaging.(3)In order to improve the resolution of the imaging system and reduce the edge illumination level,a dielectric rod antenna in the frequency band of 70 ? 110 ghz is designed,and the influence of the parameters of the dielectric rod antenna on the performance of the antenna is analyzed in detail.On this basis,a new feed antenna is designed,which has excellent performance in antenna gain and beam width.(4)The focus characteristics of the imaging system are analyzed by simulation,and the effect of focal spot distortion on the resolution is analyzed.(5)Aiming at the defect of focal spot distortion in traditional ellipsoid,a free-form surface based on Zernike polynomials is designed by combining optical imaging theory with millimeter wave imaging theory.