Tank test results of synthetic aperture sonar image reconstruction using two frequency bands

Abstract

Synthetic aperture experiments have been done in water tanks using two different frequency bands. Their center frequencies are around 25 kHz and 300 kHz, respectively. The lower frequency system has eight equally spaced receiver channels with one wavelength distance and the higher frequency one has sixteen receiver channels with about seven wavelength spacing. Five different types of structures were selected as sonar targets. They are sphere, cylinder, octahedron-shape structure, star-shape structure, and an in-plane grid target. The sphere and cylinder were floating in the water column while the others were located on the tank bottoms. As the transmitting signals linear frequency modulation was applied. Sonar images were reconstructed by synthetic aperture processing and the deviated motion from the perfect rectilinear trajectory due to the vibration of the vertical support was compensated by using motion sensor data and receiver signals. Synthetic aperture images were experimentally generated using the two different frequency bands and compared.