ISAR imaging of multiple moving targets using signals separation

The conventional motion compensation algorithms, which are designed for a single moving target, cannot be directly used to multiple targets ISAR imaging because the returned signals of these targets are overlapped in time and have low correlation. In this paper, a separated ISAR imaging method is proposed for multiple moving targets with uniformly accelerative rectilinear motion in the same radar beam. The second-order keystone transform (SKT) is used to correct range curvature for all targets without knowing their accelerations. Then the chirp rates of the signals of different targets are estimated by the Gauss Short-time Fractional Fourier transform (GSFrFT). The chirp rates of targets are different from each other. Then the returned signals of each individual target are separated based on its chirp rate in the fractional Fourier domain. Finally, after signals separation, the well-focused ISAR image of each individual target is obtained by the conventional motion compensation algorithm. Simulation results are presented to demonstrate the effectiveness of the proposed method.