Fast Moving Target Imaging And Parameters Estimation Of SAR

With the development of science and technology and the rapid progress of China's military-civilian integration,Synthetic Aperture Radar(SAR)ground moving target imaging technology is widely applied in various military and civil fields.For moving targets with large radial velocity,the problem of Doppler ambiguity results in a complicated imaging procedure.The traditional imaging algorithms cannot effectively and accurately focus the moving targets.This paper emphasizes on researching the fast moving target imaging technology with large radial velocity.In this paper,The content mainly includes the following aspects:Firstly,the geometric model of airborne SAR and ground moving target is constructed.According to the principle of electromagnetic wave propagation and the relative motion of SAR and target,the echo signal expressions of stationary target and moving target are constructed respectively.By comparison,the effects caused by different notion parameters are revealed,and the range migration phase term and Doppler parameters of echo signal are analyzed.Secondly,the range walk migration correction algorithm widely used in existing algorithms is introduced,the algorithms includes Keystone transform,Hough transform and Radon transform,meanwhile the advantages and disadvantages of these algorithms are analyzed.In order to reduce the computational complexity,a novel gradient based slope estimation algorithm is proposed in this paper.The algorithm can achieve accurate parameter estimation and save a lot of computing time.Simulation results show that this algorithm is suitable for real-time SAR imaging system.Finally,the problem of Doppler modulate rate estimation is solved.According to the fact that there are multiple targets existed in SAR observation area and some of them are located adjacent to each other,the radar echo signal is a multi-component Linear Frequency Modulated(LFM)signal.Therefore,Lv's Distribution(LVD)time-frequency analysis algorithm is adopted to estimate the Doppler modulate rate of the signal.This time-frequency analysis is free of cross terms,and has superior performance in analyzing the parameters of multi-component LFM signal.Compared with the traditional time-frequency analysis method,it can obtain the focusedimage with lower side-lobe.The simulation results show that,compared with the traditional imaging algorithm,the proposed algorithm can get better focusing effect.