ISAR imaging for targets in nonuniform rotation based on phase history decomposition

In ISAR imaging, the nonuniform rotation would induce phase errors related to the distribution of scattering centers, which can´t be compensated by a single phase error function. To solve this problem, an imaging algorithm based on phase history decomposition is proposed, which can compensate the phase errors induced both by translational motion and by nonuniform rotation of the target. Firstly, the phase histories of different scattering centers are extracted by signal decomposition and they are arranged into a phase history matrix. Secondly, we remove the effect of the translational motion by wiping the average of the phase histories off. Thirdly, the singular value decomposition (SVD) is carried out to estimate the rotation angle function of the target. Finally, the focused ISAR imaging can be obtained by compensating the translational motion and resampling the origin high range resolution profiles (HRRP). The proposed algorithm can alleviate the imaging blur caused by traditional motion and nonuniform rotation at the same time, and does not require the model assumption of the rotation. Experiments using simulated and field-measured data verify the validity of this method.