USA As Represented by Secretary of the Navy

Robert J McDonald

Jo Ellen Wilbur

Robert C Manning

Meir Gershenson

Joellen Wilbur

Lisa B Tubridy

A wideband-to-narrowband conversion method and apparatus performs the operational step of receiving an acoustic wideband signal, initially incident on an array of acoustic wideband transducers and subsequently digitized, and in response thereto generating a spatial Wigner bilinear kernel output signal, and the operational step of receiving and spatially bandpass filtering the spatial Wigner bilinear kernel output signal to remove a wideband low frequency portion as well as any unwanted noise therefrom and retain and output only a narrowband portion thereof.

Wideband-to-narrowband conversion method and apparatus

A method is provided to compress and display received data from a toroidal olume search sonar (TVSS) in terms of horizontal range. For any TVSS receive beam having a horizontal component projection that is equal to or greater than a selected horizontal range, the data values occurring at that selected horizontal range are averaged to form a compressed data value. Range dependent weight factors are applied during the averaging process so that the effects of surface and bottom reverberation do not bias the compressed data value. The compressed data value can then be displayed as a function of horizontal range for a series of sonar pings in order to provide a time history.

Image conversion for a scanning toroidal volume search sonar

An apparatus and method for beamforming for a toroidal volume search sonar. onar array vehicle motion is used to reduce reverberation by fixing beams geometrically in space to prevent beam contact, prior to a specified range, with the sea surface or sea bottom interfaces. Reverberation is further reduced by creating a composite beam from one scanned beam containing the target dominated by surface reverberation and another dominated by bottom reverberation. A correlation and averaging procedure is applied to the two scanned beams to further reduce the reverberation in the composite beam. To further reduce reverberation, the two beams selected for correlation and averaging processing are chosen such that the number of common elements associated with the two beams is a minimum within a given angular separation.

Shallow water beamforming methodology for toroidal volume search sonar

A DC superconductor quantum interference device (i.e. DC SQUID) is used in a flux-locked loop as a sensitive detector of magnetic flux. Prior art devices of this sort had a transfer function which was frequency-limited by the transfer function of impedance matching circuitry which is used to connect the DC SQUID with the first preamplifier, which amplifies the DC SQUID signal before it is applied to a detector circuit. The present invention corrects this frequency limitation by creating a compensating circuit having a transfer function which is the inverse of that of the impedance matching circuitry, and inserting it in the system after the first preamplifier and before the detector circuit.

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Panama City Beach, FL, United States of America

Robert J McDonald