PHASED ARRAY DOPPLER CURRENT PROFILER

THIS PROPOSAL REQUESTS PHASE I FUNDING TO DEMONSTRATE THE FEASIBILITY OF DEVELOPING AN ACOUSTIC DOPPLER CURRENT PROFILER (ADCP) WITH TWICE THE DEPTH RANGE OF PRESENT INSTRUMENTS. THIS WILL REQUIRE CUTTING THE OPERATING FREQUENCY IN HALF, AND DOUBLING THE TRANSDUCER APERTURE FOR EACH BEAM. TO KEEP THE SIZE OF THE TRANSDUCER MANAGABLE, WE PROPOSE TO DESIGN A NEW PHASED ARRAY TRANSDUCER WHICH WILL GENERATE ALL FOUR BEAMS FROM A SINGLE SET OF ELEMENTS, USING ONLY 90-DEGREE PHASE SHIFTS. IN PHASE I WE WILL EVALUATE THE POTENTIAL PERFORMANCE AND COST OF THIS DESIGN. CRITICAL ISSUES ARE TRANSDUCER SIDELOBE LEVELS, BEAM-TO-BEAMCROSSTALK, SIMPLICITY OF THE ELECTRICAL NETWORK, AND THE INCREASE IN SHIP'S NOISE WITH LOWER OPERATING FREQUENCIES. BOTH AN ANALYTICAL EVALUATION AND AN EXPERIMENTAL DEMONSTRATION OF A PROTOTYPE PHASED ARRAY TRANSDUCER WILL BECONDUCTED.