Research On Millimeter-wave Image Reconsruction Algorithm Of High Resolution Based On Spherical Wave For Security

In recent years,terrorist activities have occurred frequently around the world,and the international security situation is very critical.Most terrorist activities occur in crowded public places,and terrorists choose to hide explosives and other dangerous products on their bodies.The traditional security inspection technology is mainly based on metal detection and manual inspection.This method is simple and convenient,However,there are very few kinds of prohibited substances that can be detected,and the examination of human body is not comprehensive,and the safety of the security inspectors should also be taken into account.Millimeter wave is precisely to make up for the lack of existing security technology because of its penetrating characteristics.Therefore,millimeter wave holographic imaging technology for human safety inspection needs urgent research and development.In the process of security inspection,scanning and imaging time and imaging resolution need to be taken into account.Therefore,it is of great significance to improve the image resolution and save the cost of the system.In this paper,millimeter wave reconstruction algorithms are studied,and more accurate millimeter wave imaging formulas and algorithm for improving range resolution are derived.The main research contents include two algorithms:First,the traditional millimeter wave holographic imaging algorithm ignores the decay of the spherical wave with the propagation distance,Therefore,the imaging results are inaccurate.Different types of objects have different reflectivity.The same object with the same reflectivity at different distances shows inconsistencies in reconstructed images.In order to solve this problem,starting from the principle of imaging,millimeter wave holography is based on the principle of optical holography.In this paper,a more accurate reconstruction formula is derived from the angular spectrum theory in optics.The imaging algorithm can compensate for the attenuation of distance,and more accurate reconstruction images can be obtained for 2D and 3D targets.Second,in the accurate reconstruction of three-dimensional millimeter wave holography,it is found that the difference between azimuth resolution and range resolution is too large.Since the resolution of the range depends on the bandwidth of the system,the traditional improvement methods are devoted to broadening the system bandwidth to improve the range resolution.However,with the increase of system cost,new problems arise.The distance resolution improved by this method is always limited.Therefore,from the point of view of algorithm,this paper improves the range resolution without increasing the bandwidth of the system.According to the principle of millimeter wave holographic imaging,millimeter wave holographic imaging uses interference principle,not only the amplitude information is recorded,but also the phase information directly related to the distance.In the interferometric synthetic aperture radar,the phase information is used to restore the information of the target environment.The key is to expand the phase value.By using this technique,the range resolution can be significantly improved without increasing the system bandwidth.In summary,based on the principle,two-dimensional and three-dimensional millimeter wave holographic reconstruction algorithms and range resolution algorithms have been deduced.The algorithm solves the problem of the inaccuracy caused by the spherical wave attenuation in the traditional algorithm and solves the problem of too much difference between the range resolution and the azimuth resolution without increasing the system bandwidth without increasing the cost.It provides technical support for human body security imaging system to detect concealed objects accurately.