38 kHz broadband phased array acoustic Doppler current profiler

Recently RD Instruments (RDI) finished developing and demonstrating the performance of a prototype 38 kHz broadband phased array acoustic Doppler current profiler (ADCP) for deep ocean current measurement. Unlike conventional RDI ADCPs with four circular transducers, the prototype uses one flat face broadband phased array which is about the same size of one circular transducer in the conventional ADCP. The array consists of 988 individual transducers and produces four beams simultaneously. The broadband technology implemented by the prototype makes a factor of 50-100 improvement in the variance of single-ping velocity estimates over the narrow band ADCPs. The measured beam pattern, transmit source level, receiving sensitivity and the system excess noise level of the prototype were consistent with theoretical predictions. The local ocean profile data of the prototype were consistent with the theoretical analysis and the simultaneous profile data from a standard broadband 150 kHz ADCP. The prototype demonstrated profiling depth of 1000 meters limited by the local ocean depth. The analysis indicates that greater ranges are possible provided the volume scattering strength (Sv) does not decrease below -100 dB encountered at 1000 m depth during the local ocean tests.