Fast moving target imaging and motion parameters estimation based on Radon transform and bi-directional approach

摘要

Current algorithms for focusing a moving target usually adopt the quadratic approximation when expanding the range equation of the moving target. However, for a fast moving target, the cubic term of the range equation may lead to severe azimuth side-lobe asymmetry, which affects the quality of SAR image and thus degrades the recognition performance. Therefore, the cubic term cannot be ignored. In addition, motion parameters estimation is a key step for focusing the moving target, but the existing algorithms suffer from ambiguity, complex realisation, or heavy computation load while estimating the motion parameters of the fast moving target. To address this issue, this study proposes a novel algorithm for focusing the fast moving target and estimating its motion parameters. First, the cubic term of the range equation is kept and its impact on the imaging quality is analysed. Then, radial velocity estimation is converted into extracting the slope of the range walk trajectory, and the imaging quality of the fast moving target is improved by removing the effect of the cubic term. Finally, the Bi-Directional approach is utilised to estimate the along-track velocity with low computation load. Both simulated and real data are used to demonstrate the validity of the proposed algorithm.