Study On Sparse Array Space-based Radar System Analysis And Moving Target Imaging Detection Technology

Space-based radar can be used for high-resolution imaging and ground moving target detection on a global scale.The large detection range requires a high product of power and aperture which is limited for the space-based platform.And the higher detection sensitivity and resolution are required for the small target detection.These problems pose exceptional hardship for the space-based radar system research and development,and it is very important to research the sparse array system.In sparse array space-based radar system,a sparse array antenna is implemented based on the sparse microwave imaging theory,which can be used to improve radar detecting ability and achieve a high space resolution and light equipment volume and weight.In this thesis,the space-based radar system and moving target imaging detection are researched based on the sparse microwave imaging and sparse array antenna theory,and the main contributions are as follows.Firstly,the space-based radar system problem is researched.The technical system and key technology of the space-based radar are discussed based on large scale sparse array antenna,and a sparse array optimization method is proposed.The system parameters for an X band MEO space-based radar are designed and the system performance is analyzed.The SAR space resolution across track direction can be increased significantly for the same power-aperture product if the sparse array antenna transmitting wide beam and receiving narrow beam is used,which provides a new selection for the space-based radar development.Secondly,the phase error compensation between different channels is researched,which is important for the array antenna performance.A compensation method for the phase error between channels of space-based array SAR is proposed,and a cost function is constructed based on the antenna pattern and Doppler correlation coefficients,by which the estimation of the phase error between channels are transferred to the optimization of the cost function and the estimation precision is improved.The simulation results based on the RADAR-SAT data demonstrate that the proposed method is feasible.Thirdly,moving target imaging detection is a key mode of the space-based Radar.The along-track moving target detection is researched in this thesis firstly and a SAR moving target imaging technology based on the distributed compressed sensing theory is proposed.The distributed compressed sensing observation model is constructed by using the sparse property of moving targets and the non-sparse characteristics of the clutter background.The clutter background and sparse moving targets is reconstructed by optimization method,and the paired false target echoes in multi-channel SAR moving target are suppressed,by which the high-resolution wide swath SAR image can be achieved and the moving targets will be detected simultaneously.The method is verified by the simulation results based on the RADAR-SAT data.Finally,the across-track moving target imaging detection is also researched.A moving target imaging detection method based on the three-dimensional imaging technology under sparse sampling conditions is proposed,in which the MURA forward and reverse coding and the interferometric processing are implemented.The moving target detection problem is converted into a three-dimensional imaging problem,and the phase defocusing of the moving target caused by its movement across the track direction can be attenuated by the interferometric processing of the two threedimensional SAR image,by which the detection performance is improved.The sparse sampling in the range frequency domain has little influence on moving target detection,which ensures that the method is feasible.The method is verified by the simulations.