USA As Represented by Secretary of the Navy

James G Kelly

Edmund J Sullivan

Frank W Cuomo

John R Short

Martin Buffman

Robert N Carpenter

Charles R Walsh

A submergible towed body system carries an acoustic transmission/reception evice under the surface of the water and relays signals between the acoustic transmission/reception device and a surface platform. An elongated support frame has upper and lower horizontal frame sections maintained in a parallel spaced apart relationship by a plurality of vertical frame supports. A float is attached on top of the upper horizontal frame section and a tow point depends from the upper horizontal frame section. Attached to the upper and lower horizontal frame sections is a combination tilt and pan mechanism that allows the acoustic transmission/reception device to pan through a prescribed horizontal angle and tilt through a prescribed vertical angle. Circuitry is mounted between the upper and lower horizontal frame sections and aft of the tilt and pan mechanism for electrically connecting the surface platform to the acoustic transmission/reception device.

Submergible towed body system

A fiber optic bundle towed line array having a central strength member and plurality of longitudinal optical fibers spaced around the bundle near the array outer circumference. Each fiber has at least one in-line intensity modulated optical fiber hydrophone inserted at different preselected locations therealong. Patting material is molded around and embeds the optical fibers and the strength member so as to form a small diameter integral array unit.

Optic bundle towed array

A dual frequency, polymer hydrophone, array for a submersible vehicle is closed. A mid-frequency transducer array is employed in the forward end of a submersible vehicle. Between the mid-frequency array and a nose portion of the submersible vehicle is a single or multiple board piezoelectric polymer array employed to implement a secondary, high-frequency transducer array. Amplifying and signal conditioning units are mounted adjacent or on one metallic electrode layer or formed integrally thereon to minimize signal lead loss. The piezoelectric polymer material is chosen to have a density coefficient and sound velocity substantially equivalent to an acoustic window in the nose portion of the submersible vehicle and to be substantially transparent to the mid-frequency array. Minimal degradation of the mid-frequency received or transmitted signals occurs due to the transparency of the high-frequency array. Benefits of the present invention include providing wide area search capability with the mid-frequency array and high-resolution homing and object classification, among other things, with the high-frequency transducer array.

Dual-frequency sonar system

A method of acoustic processing for acoustic image classification of an underwater target from a set of known target hypotheses is provided. An acoustic waveform is transmitted into a test volume of water containing the target to be classified. The test volume is divided into test cells such that each test cell contains a portion of the target or scatterer that will scatter the transmitted waveform. Scattering of the transmitted waveform at each test cell is described by a scattering coefficient that is unique for each of the targets in the set of known hypotheses. Accordingly, the scattering coefficient serves as an identifier of the target to be classified. The relationship of the set of scattering coefficients for each of the known target hypotheses is provided by a known covariance matrix. An acoustic receive array receives a portion of the scattered waveform from each of the test cells in the test volume. This received portion is a function of the scattering coefficients of the target to be classified and the transmitted waveform appropriately time delayed by the time between transmission and receipt. The scattering coefficients at each test cell are then estimated for each of the possible hypotheses. Estimation is based upon the known covariance matrices and the receive portion of the scattering. Then, an estimation is made of the received portion of the scattering for each of the possible hypotheses. Estimation of this receive portion is based upon the estimated scattering coefficients and the time-delayed, transmitted waveform. Finally, the estimated received portion of the scattering is correlated with the actual received portion of the scattering. A high correlation is indicative of the target to be classified.

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Newport, RI, United States of America

James G Kelly