A phase steered parametric array for sub-bottom profiling

The non-linear sonar developed at Loughborough University of Technology for sub-bottom profiling now meets the specifications of the REBECCA programme [Woodward et al., 1993]. At 5 kHz it gives a source level of approximately 196 dB re 1 μPa at 1m and a beam of approximately 2.50 x 2.50, A -3 dB bandwidth of +/- 3 kHz should be available at 5 kHz, permitting pulses as short as 200 μs to be transmitted. The phase steering characteristics also appear satisfactory over a +/-20° sector. This steering capability will be further developed to ensure that the selected NLA beam incidence angle to the seabed remains constant. Sensed towfish attitude errors should therefore be dynamically correctable an one axis