Evaluation of a synthetic aperture sonar with a multi-aperture transducer

This paper presents a synthetic aperture sonar with a multi-aperture transducer. The pulse repetition frequency (PRF) is automatically modified so that conditions for both maximum search range and azimuth resolution are simultaneously satisfied. The PRF modification makes the ratio of two aperture lengths an integer, each of which is obtained for the above two conditions. Consequently, unnecessary areas on the transducer always appear at the same position, which can be eliminated for a shelter transducer. The phase errors in range curvature compensation can also be reduced by precise adjustment of the round-trip time on each aperture of the transducer. Simulation results show that over 40% of the original aperture length can be eliminated by the PRF modification. Evaluation in a test tank points out that the proposed range curvature compensation can reduce ghost targets due to phase errors.