Abstract: A method and apparatus of determining the range and depth of a far field underwater target is provided. A multi-sensor device is released into the water from a surface ship or other deploying platform and allowed to exhibit vertical free-fall in the water. Acoustic field, temperature and depth information are received from the multi-sensor device at depth points along the free-fall. The depth points from a virtual vertical aperture. The acoustic field, temperature and depth information at the depth points are inputs of a virtual vertical sensing array used to determine the range with depth of the target.

Abstract: An underwater sensing arrangement in which hydrophones are embodied in horizontally disposed arms of a hydrophone support structure adaptive to be suspended below the surface of the water and in which the support arms are elliptical and orientated so that they present the lowest resistance to horizontal flow of water past the structure and present the highest resistance or drag against movement.

Abstract: A sonobuoy suspension system is disclosed wherein a spring motor having a substantially constant output torque is mounted within an upper sonobouy unit secured to a buoyant flotation member. Formed from a coiled band, constant force extension spring wound in opposite directions about a pair of rotatable drums so that the spring is extended tangentially therebetween, the motor is coupled to a lower sensor unit by a non-compliant suspension cable for supporting the sensor unit at a predetermined underwater depth substantially isolated from the wave affecting the upper unit and flotation member.

Abstract: A top mounted buoy signaling device for marine navigation which is selectively activated in response to a coded address signal. The buoy signaling device includes a buoy having a top mounted receiver assembly which is activated by a transmitter assembly. The receiver circuit, transmitter circuit and antennas therefor are printed on circuit boards. The transmitter circuit includes an encoder chip which is preset to provide a coded address. The coded address is utilized to modulate a carrier signal to provide a coded address signal to activate the receiver circuit. The receiver circuit includes a decoder chip which is preset to the coded address of the corresponding transmitter. A lamp driver subcircuit is enabled in response to the coded address signal. The lamp driver subcircuit includes a master timer subcircuit which maintains the driver subcircuit in an operative condition for a predetermined period of time and a flash timer subcircuit which periodically energizes a lamp to provide a flashed output.

Abstract: A high frequency (HF) communications buoy that employs HF surface wave, and sky wave, communication and spread spectrum modulation to suppress multipath fading and to decrease the undesired detectability of transmitted signals. The buoy comprises a water-tight floatable enclosure that may be deployed from a flying vehicle or a submerged vessel. An HF communications transceiver is disposed within the enclosure that is capable of transmitting and receiving signals employing high frequency (HF) band surface wave and sky wave propagation. The transceiver further comprises spread spectrum modulation and demodulation circuitry for modulating transmitted signals utilizing spread spectrum modulation and for demodulating received signals encoded by means of spread spectrum modulation. The spread spectrum modulation and demodulation circuitry is provided to suppress multipath fading and decrease the probability of detection of transmitted signals.

Abstract: A sonobuoy comprising: a sonobuoy body; a main cable having a proximal end secured to the body and a distal end; a spool on which the cable is wound from the distal end toward the proximal end; and release means securing the spool to the body, and operative in response to immersion in water to release the spool from the body.

Abstract: A marine transponder system which is selectively activated to produce a predetermined signal pattern of light/sound/radio transmissions for maritime devices and structures such as navigational aids, mooring, docking or slip facilities and/or EPIRBs and other emergency signalling devices. A remote transmitter is used to broadcast an uncoded or coded signal at a predetermined frequency to activate the marine transponder system. The transponder system includes an RF receiver tuned to the predetermined frequency, and optionally a decoder unit for verifying the coded signal. Upon receipt of the transmitted frequency signal, the transponder system causes an omni-directional light/sound/radio source to be energized to produce the predetermined signal pattern. The marine transponder system may be an add-on adapted for integration with existing navigational buoys, a standalone buoy, a package configured for mounting on a dock, pier or boat, or a package adapted to be mounted on a life vest/preserver.

Abstract: A sonar array connected to a data unit includes a substantial number of hydrophone units distributed along a small diameter cable having a substantial number of connecting wires, a center strength member and a tough polyurethane jacket. The hydrophone units each include a strong metal bracket bifurcated at each end and fastened to the strength member. A generally cylindrical hydrophone member is fastened to the bracket as is a circuit board including a preamplifier and the entire unit is sealed with paraxylene resin and then molded into a smooth generally cylindrical unit which is tapered at the ends and sealed to adjacent parts of the cable jacket. To minimize the cross-sectional area and the effects of cross currents, the cable is composed of a plurality of interconnected sections, each of which is of smaller cross-section and carries fewer conductors than the section next closer to the data unit.

Abstract: A demultiplexer circuit responsive to a composite input signal from a sonobouy. The invention circuit has a filter and comparator means responsive to the composite signal for providing a filtered frequency pilot reference signal. The filtered frequency pilot reference signal has a frequency equal to one half the frequency of a reference carrier signal in the composite signal. The invention circuit has a sine demodulator means responsive to the composite signal and to an east/west demodulator signal for providing an east referenced output signal. A cosine demodulator means is responsive to the composite signal and to a north/south demodulator signal for providing a demodulated phase pilot signal and the north referenced output signal. A north/south filter means is responsive to the output signals from the cosine demodulator means for filtering the demodulated phase pilot signal to provide the north referenced output signal.

Abstract: A demultiplexer test circuit having a signal source summing means responsive to a selected target angle theta for adding a first independent noise signal to an input signal to provide a composite omni signal and for adding a second noise signal to the product of the cosine of the selected target angle and the input signal to provide a composite cosine signal, and for adding a third noise signal to the product of the sine of the selected target angle and the input signal to provide a composite sine signal. A dual output phase shifting means responsive to a selected heading angle phi provides a quad count signal, a quad count clock signal, a reference count signal and a reference count clock signal. The reference count signal is lags the quad count signal by a time interval proportional to the selected heading angle phi.

Abstract: A buoy released from an aircraft for carrying out under water listening includes a balloon fixed to a body by way of a set of halyards extending from the top to the base of the balloon and fixed inside the neck of the body of the buoy. The inflation air penetrates into this neck then into the balloon through triangular openings formed in the neck. A textile sleeve fixed to the internal wall of the neck above the inflation openings turns inside out after impact on the water so as to close these openings, which avoids deflation of the balloon and loss of the buoy.

Abstract: Motion of an instrument suspension cable assembly is attenuated in a liquid aving flow fields and surface swells. Strumming which causes vibratory motion is precluded by enclosing the cable assembly along the axis of suspension to isolate it from the flow fields. Motion along the axis of suspension due to the surface swells is substantially reduced by incorporating drag therealong on the cable assembly enclosure.

Abstract: The present invention enables tomography data in the sea to be collected and transmitted via an artificial satellite to a ground station. Accordingly, data on the Doppler phenomenon and shift of a sound wave is also obtainable based on the temperature and density of sea water and an ocean current. This makes it possible to obtain information about a wide sea area, such as the relationship between the KUROSHIO and the El nino which is now attracting attention in relation to fishery, agriculture and abnormal weather. Hence, the present invention will be of wide application.

Abstract: A sonobuoy has several components slidably mounted in an elongated tube. The components are longitudinally stacked one above the other at the lower end of the tube when the sonobuoy is in a pre-deployed state and are caused to slide longitudinally upwardly in the tube during sonobuoy deployment to provide a predetermined longitudinal spacing between the components when the sonobuoy is deployed. The components typically include an electronics canister, acoustic wave phase controls and one or more active electroacoustic transducers. The components are attached to a plurality of flexible support cables. The cables are attached at their respective upper ends to the bottom of the canister and are attached at their respective lower ends to the bottom of the tube. The cables are collapsed during the pre-deployed state and tautly extended during the deployed state. Axial guide strips are affixed to the inner surface of the tube.

Abstract: A power active filter circuit for an electric power system includes a reference generator for producing a plurality of balanced, constant amplitude, positive sequence, AC reference voltages, each being phase-locked to a corresponding phase voltage of the power system. Error signals are produced by subtracting the reference voltages from their corresponding phase voltages and a plurality of correction signals, which are proportional to the error signals, are combined with the phase voltages to produce a plurality of output voltages having substantially only a fundamental component.

Abstract: A cable driver and method for an underwater telemetry transmitter puts a signal on a single insulated wire forming part of a cable pack in which the wire is coiled and which is connected to a surface transmitting unit. The underwater transmitter includes an amplifier having an input, directly, time division multiplexed or digitally encoded from one or more hydrophones and an output into the primary winding of a toroidal transformer having a center hole through which the cable passes as it is deployed from the cable pack. The cable also passes through a similar toroidal transformer whose winding is connected to provide a feedback signal to the input of the amplifier. Since the insulated wire may be of greatly varying length and the cable pack may have greatly varying numbers of turns, the load impedance and resulting noise also vary and the above described arrangement makes the signal on the wire substantially independent of the variable load.

Abstract: An energy generator of a Sonobuoy is overlapped by a sleeve or chimney guiding gas bubbles given off by the generator to a sufficient distance from an electro-acoustic transducer of the Sonobuoy, to prevent such bubbles from coming into contact with the transducer under heaving effects. The result is suppression of unwanted noise produced by the contact between the bubbles and the transducer.

Abstract: In a system for deploying an immersible unit by a cable from a floating platform, the cable deploys freely from a cable deployment unit until a comparator unit, which provides for variable depth control, activates an anchoring unit. Activating the anchoring unit causes a jacket external to the cable to be tightened about the cable, thereby gradually braking the descent of the cable deployment unit from which the cable is payed out.

Abstract: A system for deploying an array of sonar projector transducers includes a housing in which a plurality of disk shaped projectors are stacked, a pair of small diameter cables are reeled from a powered drum for tethering the projectors, the cables being anchored to the bottom projector, a pair of electrical conductors are connected to the projectors, each conductor constituting a series of sections interconnecting electrical connectors fastened to opposite sides of each projector, a centering ring attached to the bottom projector including a series of pressure responsive latches which serve to secure the array in the housing and to release the array upon its reaching a desired depth. Where the drum is actuated the stack is lowered with each projector being successively suspended by its pair of conductor sections, and each of the conductor sections is given a predetermined twist such that when the array is again returned to the housing the conductor sections are caused to form predetermined loops.

Abstract: An automatic attenuator for use in Sonobuoy Missile Impact Location System (SMILS) sonobuoys to separate re-entry which impact signatures from other acoustic phenomena is disclosed. The attenuator for the sonobuoy device is divided into a high gain, narrow band channel for detection of ping signals and a low gain, wide band channel for detection of impact signals. The output of the two channels are summed in a summing amplifier. A switch is provided to turn off the high gain channel whenever received signals are large enough to cause a comparator circuit to activate a time which turns off the switch for 15 seconds time. Thus, the stronger impact signals are distinguished from other random signals.

Abstract: A sonobuoy has several components slidably mounted in an elongated tube. The components are longitudinally stacked one above the other at the lower end of the tube when the sonobuoy is in a pre-deployed state and are caused to slide longitudinally upwardly in the tube during sonobuoy deployment to provide a predetermined longitudinal spacing between the components when the sonobuoy is deployed. The components typically include an electronics canister, acoustic wave phase controls and one or more active electroacoustic transducers. The components are attached to a plurality of flexible support cables. The cables are attached at their respective upper ends to the bottom of the canister and are attached at their lower ends to the bottom of the tube. The cables are collapsed during the pre-deployed state and tautly extended during the deployed state. Axial guide strips are affixed to the inner surface of the tube.

Abstract: A programmable phase-locked loop frequency synthesizer for a multi-channel onobuoy transmitter is disclosed. The phase-locked loop, including a counter/divider utilizing variable modulus prescaling techniques, is modulated at its voltage-controlled oscillator (VCO) by an external signal which is preemphasized by a compensation network in order to correct for the roll-off characteristic response of the loop below its natural frequency.

Abstract: Three or more listening devices (A1, A2, A3) are dispersed over the water area where the location of a sound source is to be determined, and transmit radio signals over respective channels to a master station upon detecting sound. The master station correlates the signals from selected ones of the listening devices to derive the position of the sound source relative to those listening devices. If the positions of those listening devices are unknown, for example if the devices are floating free, their positions are determined by the master station by comparing the relative times at which an identifying radio signal transmitted by each listening device is received by the master station directly and relayed from each of two stationary radio stations with known positions. The listening devices may also be provided with receivers for receiving radio command signals from the master station, for example relating to activation of certain listening devices and assignment of radio channels.

Abstract: A sonobuoy launching system having an electrical connection device for prding a data transmission link between a sonobuoy launch tube and launch container mounted therein. Conductive metal rings are disposed on the end surface of the launch container. A contact-pin device having spring-loaded conductive metal pins is mounted in the breech end of the launch tube. The contact-pin device is oriented such that when the launch container is coupled to the launch tube each of the conductive metal pins will make electrical contact with one of the conductive metal rings.

Abstract: A seismic data acquisition system for use in shallow water covered areas comprises a flotation device which serves also to house the electronic components; anchoring device with mechanical filter device to protect the anchor, so as to insure its maintaining its position; seismic sensor device for detecting seismic waves in the water and converting them to electrical signals; radio receiver device for receiving operational control instructions; and device for amplifying, digitizing and storing the electrical signals provided by the sensor, preferably on a removable tape recording device.

Abstract: An airborne buoy droppable from an aircraft into water, comprising, as a float, a balloon which inflates during its fall. Before being dropped the balloon is protected by a hood locked by a bent blade bearing on a wedge. During the fall, the scoop-shaped mechanical parts lift up, a cloth placed below an opening in the scoops inflates and frees the hood by drawing back the wedge fixed on the tongue forming an extension of the cloth.

Abstract: A system for transferring cargo at sea by helicopter includes an automatily activated self inflatable apparatus for reducing the velocity of the cargo if jettisoned or inadvertently dropped into the sea and for keeping the cargo afloat until retrieval may be accomplished. The cargo is lifted by a support sling attachable to a helicopter suspension cargo hook and simultaneously connected to a second sling in parallel to the helicopter through the rapidly deployable retardation and floatation device. Release of the support sling causes the cargo to drop and initiate deployment and inflation of the ribs of the parachute thereby retarding the cargo's descend and providing buoyancy for its floatation.

Abstract: A system for determining the direction of an underwater discrete source of acoustic vibrations by sensing acoustic wavefronts produced thereby, which system comprises a neutrally buoyant semirigid underwater platform which may be made of a water inflated soft walled material and having mounted thereon an array of omnidirectional hydrophones arranged in a predetermined geometric pattern. Circuit means are connected to the hydrophones and an array steering means is associated with the circuit means to allow determination of the time relationship of the signals obtained from the hydrophones.

Abstract: Serving as a hydrophone in the lower unit of the sonobuoy, two surface acoustic wave resonators for determining the resonant frequency of two independent oscillators are also used to sense pressure and thus sound. The outputs of the two resonators are mixed and then passed through a low pass filter to provide a low frequency hydrophone output signal and to remove temperature induced signal distortion. A line driver and low cost twin lead transmission line provides the signal to the upper floatation electronic unit of the sonobuoy for conversion to the desired RF carrier frequency. In a single-channel sonobuoy, this signal is multiplied and amplified for transmission to a distant receiver. In a multi-channel sonobuoy, this signal acts as a reference frequency for the frequency synthesizer section of the sonobuoy transmitter.

Abstract: Disclosed is an underwater seismic exploration system utilizing a sonobuoy for the radio telemetry of seismic data signals to a remotely located receiver, the sonobuoy including circuitry for digitizing the analog signals generated by hydrophones suspended from the sonobuoy prior to the application of these signals to an RF antenna. The remotely located receiver includes an antenna for receiving the transmitted modulated digital signal information, and means for demodulating, demultiplexing, and appropriately converting the signals for either analog or digital recording of the received data.

Abstract: A buoy capable of being dropped onto water from an aircraft, comprising a balloon which inflates during the descent through a forced intake of air through adjustable openings at the base of the balloon. Inside the balloon there is a flexible membrane allowing the air to enter through holes, the balloon remaining inflated to the maximum pressure encountered during the descent. Pockets with openings are traversed by the air and prevent the balloon from rotating during its descent.

Abstract: A high resolution underwater acoustic navigation system is provided by a combined pulse and continuous-wave or Doppler system. Locations of the object being tracked are periodically determined by the pulse subsystem and are used to initialize the Doppler subsystem. The Doppler Subsystem tracks the location from the fix obtained by the pulse subsystem. Both subsystems are interfaced with a central processing unit or digital computer and the data rate input to the computer is substantially reduced by the use, in the Doppler subsystem, of a phase angle quadrant change counter whose accumulated count is periodically provided as an input to the computer.

Abstract: An active filtration system is described which may be particularly useful for filtering undesired harmonics of the fundamental AC frequency produced by AC to DC or DC to AC conversion. The filtration system of the invention produces currents of a phase, frequency and magnitude for injection into the AC system such that the undesired harmonic currents to be filtered sum with the injected currents giving a net zero current at the undesired harmonic frequency. The system can incorporate existing passive filtration elements and provides a high-impedance parallel-filtration network to prevent the filteration system from acting as a "sink" for the ambient harmonics generated elsewhere in the AC system. Because the frequency, phase and magnitude of the injected currents are controlled, the filter of the invention remains highly effective even when these quantities and the filter component values vary.

Abstract: A connector assembly such that when a first half of the connector receives a second half, a vent hole is defined therethrough. With the second half disconnected and a third half coupled to the first half, the vent hole is sealed.

Abstract: An aerodynamic housing is disclosed for stabilizing the free-fall descent an article, particularly a sonobuoy, launched from an aircraft. The housing is cylindrically-configured and includes a tail section wherein a plurality of symmetrical channels are formed obliquely to the cylindrical surface of the housing about the circumference thereof, each channel having a leading edge in the shape of a truncated ellipse. A tailring mounted at the rear of the tail section partially covers the channels thereby forming contoured air ducts through which air flows during the free-fall to orient the housing vertically and stabilize the descent.

Abstract: In a system for deploying an immersible unit by a cable from a floating platform, the cable deploys freely from a cable deployment unit until a comparator unit, which provides for variable depth control, activates an anchoring unit. Activating the anchoring unit causes a jacket external to the cable to be tightened about the cable, thereby gradually braking the descent of the cable deployment unit from which the cable is payed out.