Synthetic aperture sonar imaging based on auto-focusing method

Based on detailed analysis of causes resulting in phase errors in synthetic aperture sonar (SAS), this paper points out that the primary factors to affect our developing SAS can be ascribed to the shifts of Doppler center ( f/sub dc/) and Doppler rate (f/sub r/) for the irregular motion of the underwater carrier. Successively f/sub dc/ and f/sub r/ estimating methods in the image field based on multi-look processing are analyzed, and it is proved that these approaches are the better selections for SAS in the presence of both range migrant and partial aperture. A compensating and imaging complete SAS systemic design based on auto-focusing method is provided together with a modified range-Doppler imaging algorithm and a refined compensating step based on the PGA algorithm, and it is proved that this design is effective by real lake trial results.