Synthetic aperture beamforming with automatic phase compensation for high frequency sonars

The author discusses a phase compensation technique suitable for both high- and low-frequency sonars using displaced phase center receive elements to compute phase corrections directly from the acoustic scene. The phase compensation corrects ping-to-ping incoherence due to both medium and vehicle motion instabilities over the integration period of the synthetic aperture, thereby improving image quality. The phase compensation technique was evaluated using both simulated hydrophone data and acoustic test tank data at 550 kHz. General-purpose beamformers have been developed to allow side by side comparison of physical aperture and synthetic aperture images processed from the same set of hydrophone data. Performance results are presented for both simulated and acoustic test data, depicting the improvements provided by this phase compensation method