An efficient range alignment method for long-range ISAR imaginig

For the inverse synthetic aperture radar (ISAR) imaging of a target at a long range, range alignment using existing methods bring about poor results. This paper proposes a three-step range alignment to solve the problems of the existing methods. After coarsely aligning the range profiles using the center of mass of each range profile, range bins irrelevant to the target are removed by thresholds to narrow the search space. Then fine alignment is carried out using the entropy minimization method. An optional particle swarm optimization can be used to further fine-tune the aligned range profiles. This method is computationally more efficient and preserves the image quality.