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Inverse Synthetic Aperture Sonar Imaging of Underwater Vehicles Utilizing 3-D Rotations

Inverse synthetic aperture sonar (ISAS) can obtain the image of a moving underwater vehicle (UV) with both high range resolution and high cross-range resolution. Existing ISAS imaging methods are based on the translational motion of the UV. Since a real UV also does 3-D rotations, these methods suffer from defocusing especially in severe sea condition. Hence, a novel ISAS imaging method utilizing the 3-D rotations is proposed in this paper. Under the 3-D rotational model, the echo in slow time is simplified as an amplitude modulated-cubic phase signal (AM-CPS), and a high precision signal parameter estimation algorithm based on the Radon transform cubic phase function is presented to process the AM-CPS. Moreover, the image plane is analyzed. The result shows that the ISAS imaging method based on the 3-D rotations can obtain the target's images on more image planes compared with the translational motion based methods, and the image quality is improved compared with other signal parameter estimation algorithms. The simulation verifies the effectiveness of the proposed method.