Towards development of autofocusing schemes for phase compensation of synthetic aperture sonars

This article is dedicated to the phase compensation problem associated with synthetic aperture sonar beamforming. Array movements during the time of synthesis and medium heterogeneity have to be compensated at a degree of accuracy of a fraction of wavelength to achieve the full resolution expected from theory. We present a phase noise correction scheme based on 2D correlations of conventional beam signals coming from adjacent pings. Successful compensation of ping to ping lateral displacement amplitudes up to 75 /spl lambda/ have been achieved by the proposed method on DUBM-42 actual sonar data (the DUBM-42 is a French Navy owned high resolution side looking imaging sonar at 400 kHz).