Research On Millimeter Wave Imaging Of Target Object And Electromagnetic Parameter Extraction

Aiming at the current situation of security inspection and the development and application of millimeter wave imaging technology in China,the principle of millimeter wave imaging technology has been studied in depth,and the algorithm of millimeter wave imaging has been deduced in detail.On this basis,the millimeter wave imaging of metal and non-metal targets and the accurate estimation of electromagnetic parameters of non-metallic dielectric objects are realized.At the same time,the millimeter wave imaging experiments for various objects are built and carried out.The prototype of millimeter wave test system has designed preliminarily.The main research objectives of this thesis are as the follows.(a)Basic Millimeter Wave Imaging Theory and Target Detection Algorithm.The basis of SAR imaging theory and the scenario of different working mode have studied,the resolution of distance and orientation of SAR imaging are analyzed,and the image reconstruction of single frequency point and broadband millimeter wave have studied.The basic principle of convolution neural network and the implementation process of target detection of SSD algorithm are introduced.(b)Implementation and Simulation of Millimeter Wave Imaging Algorithm for MIMO Array.The basic theory of MIMO array millimeter wave imaging has been introduced.It has listed the detailed derivation process,and have compared with the method of cylindrical scanning way.Through the simulation experiments for different frequency band widths,the different angle parameters and the different imaging system parameters,the influence between the imaging and the shortest distance and minimum angle of adjacent antennas have been analyzed.The relationship between the resolution in all directions and the parameters of MIMO imaging system is also achieved.Based on imaging algorithm,it is realized the imaging of metal and nonmetal target objects,the experiments of target recognition and detection for pistols and daggers are also carried out,the experimental results verify the feasibility of target detection algorithm applied to millimeter wave imaging system.(c)A Method of Extracting Electromagnetic Parameters Based on Millimeter Wave Imaging.It has deduced the method and principle of electromagnetic parameter estimation of target object based on millimeter wave imaging,and the simulation experiments are carried out with lossless and lossy media objects.The feasibility and correctness of the method are verified by measuring the electromagnetic parameters of common blocks in real life.(d)Construction and Measurement of Near-Field Millimeter Wave Imaging System.It has introduced the construction method of millimeter wave imaging system,and present the test problems and key points that need to be paid attention to in the process of construction and actual measurement,at the same time,on this basis,gives the actual measurement of the target object,and illustrates the feasibility of the construction of imaging system.A preliminary measurement platform for MIMO imaging system has been designed.The design drawings and instructions are given,and the recommended sample parameters are provided.