Research On Moving Target Detection For Near-space Hypersonic Vehicle Borne SAR

Near space hypersonic vehicle(NS-HV)is a high-speed aircraft operating at 20 ?100 kilometers of airspace on the surface of the earth at a speed exceeding Mach 5.NS-HV can reach any place of the world within one to two hour,making it possible to detect the targets of opportunity with random appearance and short duration in any place.Moving target detection(MTD)of NS-HV borne synthetic aperture radar(NH-SAR)is the core technology to realize this function.However,the extremely fast speed of NH-SAR platform causes the clutter spectrum to be severely broadened,which results in the constrained performance of traditional MTD methods such as DPCA,ATI,and STAP.Therefore,there is an urgent need to study MTD methods for NH-SAR to meet the needs of NS-HV rapid strike.In this thesis,the theoret-ical analysis,method research,and simulation experiments are systematically performed on the problem of NH-SAR moving target detection.The main contents are as follows:1.Quantitatively analyses the influence of the ”stop-go-stop” hypothesis on NH-SAR imaging and positioning,and derives the boundary conditions for the application of the ”stop-go-stop” hypothesis in NH-SAR imaging.The characteristics of NH-SAR echo signal-to-noise ratio(SNR),point target distance and Doppler spatial variation are analyzed,and the problems of low NH-SAR echo SNR and strong variability are pointed out.2.NH-SAR moving target echo model is established,and the defocus and offset calculation formulas of the moving target in the SAR image are derived.The application range of NH-SAR signal domain and image domain MTD methods is analyzed and its detection performance is evaluated.The essential reason for the limited performance of traditional SAR MTD methods is revealed.3.A Track Before Detect(TBD)MTD method based on multi-frame image se-quences is studied.The relative relationship between NH-SAR image frame rate and detectable speed under different operating conditions is analyzed.The TBD model is established and the algorithm flow is established to achieve NH-SAR moving target de-tection.Compared with the traditional MTD method,this method significantly improves the low-speed target detection performance under low SNR condition.4.A signal-image domain joint moving target detection method for NH-SAR is pro-posed.A fast-moving target signal domain and a low-speed moving target image domain joint detection model are constructed.The NH-SAR wide-range moving target detection task is completed.At the same time,The multi-level image sequence extraction method is further reduced,which further reduces the minimum detectable speed of the system and improves the detection performance.The above models and methods have been verified through theoretical analysis and simulation experiments.The results show that the above method can achieve the detection of SAR moving targets on near space hypersonic vehicles and expand the detectable speed range of moving targets for NH-SAR.