Study On Ground Moving Target Indication And Localization For Hybrid Baseline Array

Ground moving target indication (GMTI) is an important technique widely used in both military and civilian field, and it is always a cutting-edge and challenging research topic all over the world. In order to enhance the performance of GMTI, Space-time Adaptive Processing (STAP) technique is adopted to enable airborne radar to suppress strong clutter. Spaceborne interferomatric synthetic aperture radar system utilizes the formation flying of multi-satellites to measure terrain digital elevation model (DEM) and provide the possibility of large-scale surveillance, spying, target tracking and target position. Normally airborne radar and spaceborne radar work in non-ideal array configuration to implement multi-task.Airborne radar and spaceborne radar can significantly improve the performance of GMTI. However, there are many challenging problems when they are working in non-ideal array configuration. Ground clutter of airborne non-sidelooking radar is notâ…¡D due to different range gates, and clutter spectrum spreads in angle-Doppler domain. In the current InSAR/GMTI system, due to influence of the long hybrid baseline, the degree of freedom (DoF) of clutter patches increases drastically, which leads to the difficulty of clutter cancellation. On the other hand, the phase induced by the moving target couples with the phase of the terrain, which also cause problems in the estimation of ground target velocity. In this dissertation, aiming at the key points for irregular configuration, we deeply discuss the signal processing methods to suppress clutter and achieve satisfactory accuracy of GMTI. The main contributions of this dissertation are as follows:1. In chapter 2, the clutter and signal models are given for non-sidelooking and hybrid baseline configuration. The effect of clutter suppression and GMTI is analyzed while the phenomena induced by increasing of clutter DoF and phase coupling are discussed. The above analysis and further discussion provide the theory foundation to suppress clutter and GMTI effectively.2. The clutter has range dependence for non-sidelooking radar in short range gates, hence directly using these data to estimate the clutter plus noise covariance matrix depresses the ground moving target indication (GMTI) performance. To solve this problem, a new strategy based on least square algorithm is proposed. The method uses least square to conform short range clutter and knowledge based on radar navigation data is not necessary. It is robust in factual environment with array errors. The experimental results demonstrate the effectiveness and feasibility of the method.3. For Subsequently, a novel approach of GMTI and velocity estimation based on InSAR system is presented. Under the circumstance of terrain interferometric phase and velocity phase coupling, this method uses the coherence information of neighboring pixel pairs to compensate terrain interferometric phase. To suppress the increasing clutter degree of freedom with the terrain induced by long across-track baseline, the joint pixel method is applied to improve the performance of GMTI and accuracy of velocity estimation. The validity and superiority of proposed algorithm are verified by the computer simulation.4. For InSAR together with GMTI system, the problem is that the terrain interferometric phase coupling and the non-stationary clutter induced by the long across-track baseline arise. To avoid these problems, an alternative GMTI method is addressed. Coherence information to coregister two SAR images is applied, and then the local flat-earth phase is removed to compensate the terrain interferometric phase, finally suppression of the non-stationary clutter is achieved. Thereby, the GMTI function is well implemented in the existing InSAR system. Compared with conventional methods, the performance of target detection can be enhanced and the accuracy of velocity estimation can be greatly increased. Theoretical analysis and real data illustrate the effectiveness and practicability of the proposed GMTI method.5. A new algorithm is presented to detect moving targets in airborne side-looking SAR system. In this method, the spectrum estimation method is applied and can easily achieve a better accuracy of target radial velocity, especially in the condition of low signal-to-clutter ratio (SCR). It is shown that both Capon method and MUSIC method for velocity estimation can be unified to a simple combination by the power of R (POR) method. The unified framework of spectral-based estimation method is presented. Encouraging simulation results are given to demonstrate the effectiveness of the method. Furthermore, it is shown that multiple moving targets within same resolution cell can be distinguished by using the proposed method. The validity and practicability are verified by the simulation and real-test data.