A wide-band sonar for underwater acoustics measurements in shallow water

Defence Research Establishment Atlantic is developing a free-floating wide-band sonar for collecting acoustic data in the open ocean. The transmitter, a parametric array, offers three advantages: wide bandwidth (1-10 kHz), narrow beamwidth (/spl sim/3/spl deg/), and virtually no sidelobes. These features make the parametric sonar the ideal tool for direct measurements of environmental parameters in shallow water. By direct the authors mean the absence of complications resulting from unwanted interactions of the acoustic pulse with ocean boundaries. To complement the narrow-beam active sonar, a 6-channel superdirective/intensity array is being developed for the receiver. A 900 MHz RF command link is used to steer the array to any combination of azimuth and tilt angle. Along with control over azimuth and tilt angle, the sonar is instrumented to monitor depth, roll and vertical acceleration. Data transmission back to the ship is accomplished via a 2.3 GHz RF data link capable of a data transfer rate of up to 8 Mbits/sec. This paper presents an overview of the system.