Abstract: The invention as disclosed is of a method to authenticate identify and trace sonar transmissions and echoes by embedding transparent, secure and robust digital watermarks in signal space, where the additional information incurs no cost in bandwidth. The complex short time Fourier transform is selected as the domain for embedding the digital watermark, secured by a secret key, in the time frequency representation of the signal. The watermark is designed through an iterative optimization step. This step insures that the watermarked sonar is also realizable. Selection of the time frequency region for watermarking is driven by avoidance of interference with the sonar itself, or in case of network operation, other watermarks. In addition, the selected time-frequency region remains robust to sound channel and other transmission effects. Sonar echoes are authenticated in the time-frequency plane by a correlation receiver tuned to the watermarked region using the secret key.

Abstract: A method for determining the likely range and depth of an acoustically radiating source in which characteristics are used from hypothetical ranges and depths. A received sonar signal is compared with modeled ranges and depths. The correlation between the received signal characteristics and the modeled characteristics gives the likely range and depth. In a preferred embodiment this is presented as a contour plot.

Abstract: A system for close range sonar is provided. The system provides sufficient warning to permit maneuvering to avoid a close encounter even in the forward starboard/port regions, which have been problematic in the past due to ownship noise. The system utilizes a hull mounted sonar array and a towed sonar array which may be controlled in position to provide sufficient separation of noise received by both sonar arrays such that the noise is largely uncorrelated. The system utilizes beamformers for each array to supply a cross-correlator section which is able to minimize the ownship noise and maximize the signal thereby providing more time for maneuvering. The system also provides a LOFAR display and other displays that are highly sensitive to detecting close encounters.

Abstract: A method and system for processing received sonar signals. The method and system generate bearing data signals based on the received sonar signal. The method and system continuously determine the signal strength of the received sonar signal and also continuously determine the total noise from the received sonar signal in the ocean environment in which the target is located. The method and system provide a sensor gain in response to the determined total noise and the signal strength, and adaptively calculate filter coefficients from the sensor gain and the determined total noise. The method and system also filter the generated bearing data signals using a filter having the calculated filter coefficients.

Abstract: A system and method for displaying sonar data are disclosed. In a presently preferred embodiment, each of N channels from a beamformer are separately processed utilizing a pair of passive broadband detection processors such as SCOT processors and SPED processors. The output of each SCOT processor and each SPED processor are scaled, aligned, and then compared. The maximum scaled and aligned output from each pair of processors is selected for input to a bearing time history display.

Abstract: A system and method for displaying sonar data are disclosed. In a presently preferred embodiment, each of N channels from a beamformer are separately processed utilizing a pair of passive broadband detection processors such as SCOT processors and SPED processors. The output of each SCOT processor and each SPED processor are scaled, aligned, and then compared. The maximum scaled and aligned output from each pair of processors is selected for input to a bearing time history display.

Abstract: A system is disclosed that provides. a sonar operator with the most likely range to a target of interest. The system generates and displays a contour based on ship's parameters, target parameters, environmental data, and operator parameters. The sonar operator can vary many of the parameters in “what if” scenarios so as to generate groups of contours for preselected probabilities of detection. Contours can be used to show the actions that should be taken to ensure a favorable outcome.

Abstract: A retractable sensor array system is used to provide a large aperture sen array, such as a sonar array, that receives acoustic energy in a deployment medium. The retractable sensor array system includes one or more sensor array sheets having one or more sensors and a sensor array positioning mechanism for deploying and retracting the sensor array sheet from a platform, such as a ship, submarine, aircraft, space vehicle or medical device. The sensor array positioning mechanism preferably includes a motor that automatically and selectively deploys and retracts the one or more sensor array sheets by rolling and unrolling the sensor array sheets. The retractable sensor array system allows the one or more sensor array sheets to be deployed from various locations on a platform and also in various directions from the platform depending upon the desired usage, platform orientation, position and deployment medium conditions.

Abstract: Disclosed is a sonar system comprising a platform, axially extendable supts projecting from the platform, a flexible cable array deployed from the platform means through said support means, and an acoustic detector connected to the flexible cable. By increasing the physical aperture of the sonar system, performance is enhanced.

Abstract: An acoustic receiver assembly includes a first tubular body and a multiplty of first acoustic receivers disposed on an outer surface of the first body. A second tubular body is slidably movable in the first body and is extendible therefrom. A multiplicity of second acoustic receivers is disposed on an outer surface of the second body, the second acoustic receivers being receivable by the first body.

Abstract: The present invention relates to a system and a method for determining the earing of an object located at a distance from a reference point. A plurality of sensors are mounted to a body to detect signals emanating from the object and to convert those signals into electrical signals. The electrical signals are then processed to determine the bearing of the object from the body. The system can include a float with the body suspended from said float immersed in a fluid medium. A method for processing the electrical signals and generating the bearing information is also described.

Abstract: A decoy capable of assuming the shape of a water craft comprises a maneuvble vessel, having a tubular body portion which defines an enclosed interior region. The vessel further has an opening formed in the body portion and a hatch door which covers the opening. An energy source powers the operation of the vessel, and a drive module propels the vessel under the water. A selectively deployable bladder is stored within the vessel in its interior region and is selectively deployable from a stowed position in which the bladder is contained within the interior region of the vessel to a deployed position in which the bladder exits the vessel through the opening and is inflated with gas for assuming the shape of a water craft. An inflation system inflates the bladder with gas when deploying the bladder. The decoy can also be provided with electromagnetic, infrared and acoustic decoy projectors for projecting the characteristics of the water craft.

Abstract: A vessel, such as a submarine, has onboard sensor processing, display, and omputer control capability for an array of sensors deployed from the vessel. The array includes a plurality of cables containing numerous sensors on each cable. The cables are suspended vertically from a housing on reels that provide a convenient means for deployment and recovery of the array. A submersible means at the lower end of the cables includes active transducers, propulsion devices and control surfaces for orienting and driving the structure so as to maintain a speed and direction for this structure corresponding to that of the vessel.