Traditional security check technology is mainly based on metal detection by manual inspection. This method is simple and convenient, can detect a few different kinds of contrabands, and also takes into account the safety of inspectors. Because of its strong penetration characteristics, millimeter waves make up for the deficiency of existing security check technologies. Therefore, it is urgent to research and develop millimeter wave holographic imaging technology for human security inspection. In traditional imaging methods, the azimuthal resolution can be improved through various methods of image processing, but the traditional way to improve the range direction resolution is to increase the system bandwidth. However, improvements of the system bandwidth will greatly increase the cost. The bandwidth improvement space is also limited, so it cannot be expanded indefinitely in practical applications. In this study, the interferometric synthetic aperture theory was used to improve the range direction resolution of 3D millimeter wave holographic images without improving the system bandwidth. Phase unwrapping was used to reconstruct the phase information of complex images and restore the continuous phase distribution of the target object so as to achieve improvement of the range direction resolution without increasing the system bandwidth. This work has theoretical guiding significance to improve the range resolution of millimeter wave imaging.
Range resolution enhancement of WISDOM/ExoMars radar soundings by the Bandwidth Extrapolation technique: Validation and application to field campaign measurements
