Research On Moving Platform Millimeter Wave Radar SAR Imaging

Compared with the traditional radar system composed of discrete devices,the monolithic miniature millimeter wave radar has obvious advantages in volume,weight,cost and power consumption,which is more suitable for near-range environment sensing scenes such as unmanned vehicles and UAVs.In recent years,more and more attention has been paid to unmanned driving,security monitoring and life detection.The development of synthetic aperture technology has greatly improved the ability of radar perception,and can work without the influence of weather and light.It has the characteristics of all-weather and all-time.It makes up for the short board of vision sensor,and is widely used in military,geographic exploration and other fields.Therefore,it is of great significance to realize the micro SAR imaging system with a single millimeter wave radar.Firstly,the basic principles of FMCW radar and SAR imaging are introduced,and the geometric relationship in the imaging process and radar imaging resolution are described.Based on 77 GHz millimeter wave radar and guideway system,a miniature synthetic aperture radar imaging experimental system is built as a platform for data acquisition.Secondly,the range doppler algorithm and the back projection algorithm are introduced respectively.The principle and process of the algorithm are explained.The point target simulation is carried out and analyzed.Then the measured data are collected in different scenes using the built experimental platform.The imaging results are obtained and analyzed after the algorithm processing.The applicability of the imaging algorithm in the near-range scene is verified.Finally,in order to solve the problem that the phase error caused by the motion process will affect the imaging quality,the source and classification of the error are introduced,and the influence of different kinds of errors is explained in the simulation.Then the self focusing algorithm is introduced,including the minimum entropy self focusing algorithm and the phase gradient self focusing algorithm.The phase gradient self focusing algorithm is widely used because of its good robustness.Due to the defects of the classical phase gradient autofocus algorithm in the process of point selection and estimation error,the algorithm is improved.The sliding window is used to calculate the evaluation value for point selection.The simulation results are compared with the original algorithm to improve the algorithm performance in the presence of interference.Finally,the measured data are processed and analyzed,and the results show that the image quality is improved.