SBIR-STTR Award

A study is proposed in which the performance of an underwater acoustic vector sensor (AVS) containing conventional piezoelectric transducers is compared with that of an AVS containing single crystal piezoelectric transducers. An acoustic vector sensor is a device that measures three orthogonal components of the acoustic particle velocity in conjunction with the acoustic pressure at a single point in space. The sensor employs unimorph bender disks to measure pressure and bimorph bender disks to measure velocity. The size of each device is the same, so the chief parameters that will be evaluated are the sensitivity and bandwidth. Acoustic vector sensors are being planned for use in tactical underwater surveillance platforms that are operated by the U. S. Navy.

Benefits:
Improve performance of tactical underwater surveillance platforms operated by the U. S. Navy.

Keywords:
Acoustic vector sensor, single crystal piezoelectric , conventional piezoelectric

Acoustech plans a two-year effort aimed at evaluating acoustic dyadic sensors for prospective use in directional sonobuoys utilized by the U. S. Navy. The chief sonobuoys targeted in this study are the AN/SSQ-53 DIFAR, AN/SSQ-77 VLAD, and AN/SSQ-62 DICASS units. The DIFAR and VLAD buoys are passive devices that have a bandwidth of 5 - 2400 Hz, whereas the DICASS buoy is an active device that has a bandwidth of 6.5 - 9.5 kHz. All of the sonobuoys contain an orthogonal set of vector sensors of various designs (i.e., dipole hydrophones) and an omni-directional hydrophone (i.e., the so-called scalar sensor) to determine the bearing of a submerged submarine in the horizontal plane. Nevertheless, the overall intent of the project is to integrate dyadic sensors and the associated signal processing techniques into existing sonobuoy systems so that they have improved directivity and greater noise rejection without changing the aperture. Of particular interest is using scalar, vector, and dyadic sensors in a synergistic fashion to form the cardioid-squared beam pattern, which has a 3 dB beam width of 94 degrees. This represents a step gain in performance over current sonobuoys that exploit the cardioid beam pattern, which has a 3 dB beam width of 131 degrees. The use of piezoelectric single crystals will play an important role to support development of small transducers that exhibit high sensitivity and low noise. A step gain in performance over current directional sonobuoys can be achieved if dyadic sensors are used in conjunction with the existing sensors they employ. It is speculated that the historically large scale production of sonobuoys (e.g., over 10,000 units per year) will drive the cost of single crystal transducers to economically viable levels that are consistent with those associated with conventional PZT

Keywords:
dyadic sensor, directional sonobuoy, cardioid-squared beam pattern, single cyrstals, piezoelectric transducers, difar, vlad, dicass