Abstract: An optical correlator using a light emitting diode array, in which analog gnals from two spaced sensors are correlated in order to locate and track a target. One signal is clipped and digitized and clocked through a shift register, and the other signal is delayed. The shift register is coupled to an LED array, element for element. Each shift register element modulates its corresponding LED element. The delayed signal is also connected at its output to the LED array via a transistor, and modulates each LED element. Therefore, the LED elements emit light in proportion to the product of the two signals. The emitted light is focused onto a CCD imaging array where it is integrated over a period of time before being sent to an integrator and output display device. The output is the correlation function versus the time delay between the two signals. Successive outputs display the movement of targets. Circuit design mitigates inherent errors within the system.

Abstract: A method of determining the bearing "S" of a signal transmitter relative to a remote signal receiver. A signal pulse having a high signal to noise ratio is transmitted and sampled at closely spaced receivers displaced from the transmitter by a distance "D". Sampled phase components are derived at each receiver by deriving in-phase and quadrature components of the sampled pulse and by deriving the arctangent of each such component. The arrival time of the sampled pulses is measured by applying a least squares Gaussian fit to the modulus or to the amplitude envelope of the pulse samples. The difference ".delta.t" between the time of arrival of the pulse at each receiver is determined and then the approximate phase difference 2.pi..omega..delta.t between the sampled pulses is determined where ".omega." is the carrier frequency of the transmitted pulse. The phase difference is then applied to resolve the phase ambiguity of the phase components and the bearing "S" is then calculated.

Abstract: In a displacement measurement system using waves in the sonic to ultrasonic range, a constant wavelength of the sonic or ultrasonic wave is established by driving the wave transmitter by a variable frequency oscillator whose frequency is varied as a function of a control voltage. The control voltage is varied as a function of the phase differential between the wave transmitted by the transmitter and the wave received by reference receiver to maintain both waves in phase.

Abstract: A directional microphone apparatus includes an array of at least three sets of microphone units, circuits for processing the output signals from the microphone units to produce a first signal which varies in accordance with the second order bidirectional sound pressure gradient characteristic of the array, weighting circuits for applying respective weighting coefficients to the output signals from the microphone units in accordance with a desired shape of directivity response characteristic, to produce corresponding weighted signals which are combined to form a second signal. The first and second signals are combined to produce an output signal which exhibits sharp directivity even at relatively low frequencies in the audio range.

Abstract: A goniotelemetry system comprises two acoustic goniometers directed along two perpendicular axes taking measurements of angles at the intersection O of the two axii, as well as a triaxial magnetometer and a magnetic field gradientmeter situated at this intersection O.It allows to localize marine craft simultaneously from their radiated acoustic noise and from their disturbance on the ground magnetic field in order to fire underwater mines.

Abstract: The detection of low-flying aircraft is accomplished using both a microphone and geophone as sensors and a signal processing system for measuring the correlation between the seismic and acoustic signals. The signal processing system contains two amplification and band-limiting circuits, a delay circuit, an adaptive noise cancelling circuit, two signal smoothing circuits and a comparison circuit. The two amplification and bandlimiting circuits enhance a selected portion of the seismic and acoustic signals received by the sensors. The optional delay circuit is applied to the input acoustic signal, allowing the user the option of sensing or rejecting the detection of jet aircraft. The adaptive noise cancelling circuit generates an error signal by subtracting the signal components which are correlated between the seismic and acoustic signals from the input seismic signal. The first signal smoothing circuit improves the quality of the input seismic signal for comparison.

Abstract: An apparatus for determining an angle of incidence of a received signal utilizes two widely spaced interferometers with equal length crossing baselines. The time differential of a signal arrival between the two elements of each interferometer is established and the difference between the two time differentials is determined. Multiplying this difference by a predetermined constant provides the desired angle.

Abstract: A system insensitive to nonspeech sounds utilizes a pair of spatially separated microphones to obtain the direction of origin of speech signals from a common sound source. The speech signal from each microphone is transformed into a pulse representative signal having a rapid increase responsive to pitch peaks of energy from the sound source. The cross correlation of these pulses accurately reflects the phase relationship between the speech signals arriving at the microphones. The cross correlation is implemented as time interval histograms which are periodically read to identify the direction of the common sound source.

Abstract: An acoustic direction finding method utilizes correlation between the signals of plural sound pickups on a rotating base. As the base rotates the pickups receive signals from a source of sound which is the target for which direction information is to be obtained, these signals are shifted in time from one pickup to the next. The base is rotated substantially at constant speed with one full rotation being divided into a plurality of angle sections. The pickup signals are correlated in the individual succeeding angle sections, thus obtaining a correlation function with a correlation peak corresponding to the target direction for each angle section. The correlation functions of the same angle section are added to each other with successive rotations of the base. A curve generated by the correlation peaks is then smoothed and utilized to determine the direction of the target.

Abstract: An ultrasonic defect detection assembly (A) and an elongated workpiece (B) are mounted for relative movement. A mechanical assembly (C) provides relative movement between the workpiece and the examination assembly. An electronic circuit and display (D) produces a visual display indicating the relative position of the workpiece and the examination assembly, particularly the relative positions at which the examination assembly detects defects. A transmitting ultrasonic transducer (30) and a receiving ultrasonic transducer (38) are acoustically coupled with the workpiece, one being mounted at a preselected position on the workpiece and the other being mounted for relative movement with the examination assembly. The relative position of the workpiece and examination assembly is determined by measuring changes in a characteristic of the acoustic wave traveling between the transmitting and receiving transducers.

Abstract: A range measurement system for a submarine also having a passive monitoring system with a beam forming circuit, one beam of which may be selected by a signal V.sub.N from a tracking computer. Two assemblies of three hydrophones are located respectively on the port side and on the starboard side of the submarine. The signals supplied by these receivers are correlated with a beam signal S.sub.V of the passive monitoring system selected supplying the delays of these signals. A computer receiving these delay values supplies to the tracking computer the values of the bearing angle .alpha. and the distance D of the noise source.

Abstract: A multi-detector intensity interferometer includes plural radiation detectors positioned in a predetermined geometric array. Incoherent radiation signals from a body are received by the respective detectors, time-delayed relative to one another, and the time-delayed signals are fed to a multiplier circuit. The multiplier circuit produces an output signal comprising the product of the time-delayed signals from each of the detectors. This output signal is then integrated by an integrator circuit. A significant output signal is produced by the integrator circuit only when the time-delays of the respective detected signals correspond to the location of the object relative to a reference location. In a preferred embodiment employing at least four such detectors, the three-dimensional coordinates of the body relative to a reference coordinate system can be determined from the time-delays.

Abstract: A narrow band compensating beamformer for a receiving array that conforms some surface other than a plane and thus is, in general, three dimensional. The array comprises a number of sensing elements arranged in a non-planar pattern. Each sensing element has its output signal delayed or phase shifted as a function of the receiving angle by the beamformer in such a way as to produce an equivalent "projected planar array" in a particular direction. This arrangement has the same beam pattern in the selected direction as an equivalent planar array with its lower side lobe characteristics permitting the taking of advantage of well known, low side lobe shading techniques.

Abstract: A fish sonar is capable of detecting ultrasonic waves from a desired direction by shaping the waveforms of the outputs of a pair of vibrators spaced apart by a certain distance, and detecting a delay of the output from one of the vibrators with respect to that of the other of the vibrators so as to detect the direction of the ultrasonic waves coming to the pair of vibrators and to delay the output of the other of the vibrators with respect to the output of one of the vibrators.

Abstract: A plurality of acoustical transducers such as microphones are placed in appropriate array so that they are capable of detecting sonic energy emanating from an acoustical source such as an aircraft or a ground vehicle. The outputs of the transducers are sequentially sampled and multiplexed together, the time multiplexed signals then being converted from analog to digital form in an analog/digital converter. The output of the analog/digital converter is fed to a fast Fourier transformer (FFT), which transforms these signals to Fourier transform coefficients represented as real and imaginary (cosine and sine) components. The output of the fast Fourier transformer is fed to a digital processor. In this processor, the power and phase of each frequency bin for each microphone output is determined and the phase differences between signals received by pairs of microphones for each frequency bin of interest are determined.

Abstract: A device for determining the position of a sound source includes a plurality of sensors disposed on an object for which the sound source is to be detected and organized in the form of a matrix with N rows and M columns. The sensors are connected in parallel through respective uni-directional transmission elements with a common terminal for each row and each column. A signal processing circuit amplifies and carries out a designated output waveform generation process on detected signals produced by the sensors.

Abstract: A signal processor for use with an array of antenna elements comprises a plurality of pairs of receiver channels which receive signals from respective halves of the array. The component of the signals resulting from noise, such as the noise generated within the ocean, is substantially decorrelated between the respective halves of the array, while a component of the signal obtained from a source of a desired signal is coherent between the two halves of the array. The signals in each pair of channels are translated to intermediate frequencies by mixing the signals with reference signals of differing frequencies in each of the respective pairs of channels. The translated signals in each pair of channels are then multiplied together to produce a signal of substantially constant amplitude which is suitable for detection, or for a bearing deviation indication.

Abstract: Apparatus for locating an acoustic source which includes a pair of gradient microphones each of which is adapted to receive an acoustic wave on one axis with the two axes of the microphones being orthogonal to one another. Processing means are included for receiving first and second signals from the two gradient microphones in comparing the phase of the two signals, whereby alarm means are provided for producing a signal identifying a change in state of the phase comparison. Upon the change in state of the phase comparison, from either mutually in phase or mutually out of phase with one another, the point of closest proximity to the sensor is determined.

Abstract: A delay line time compression correlation circuit for correlating two sets of serial data is disclosed, and includes a counter for defining the number of data pairs that have been correlated and the amount of time shift between the two sets of serial data. The two sets of serial data are digital samples of two clipped analog input signals which are simultaneously sampled as a function of the correlation count value. The samples are stored and serially cross-correlated with predetermined time displacements between the two sets of data. The correlation results for each particular time displacement are summed with such total being provided as an output while the correlation for the subsequent time displacement takes place.

Abstract: 2. In a combination, a transducer for an underwater object locator comprising a plurality of radiating elements, each element comprising a magnetostrictive member having a plurality of separate windings thereon, a first winding of each of said elements being connected in series for radiating a signal, a second winding of a first one-half of said elements being connected in series to form a first channel for receiving reflected signals, corresponding second windings of the other half of said elements being connected in series to form a second channel for receiving reflected signals, means responsive to the difference in amplitude of signals in said channels to provide azimuth information of a reflecting object, and means responsive to the difference in phase of signals in said channels to provide elevation information of such object.

Abstract: A positioning determining system using a delay element and driver transducer for producing a traveling wave in the delay element, the presence of a traveling wave being detectable by a receiver transducer for determining the relative positions of the driver and receiving transducers. In accordance with the invention, a driver transducer, the delay element, and a second transducer form a self-excited feedback loop oscillator, the frequency of oscillation of which is determined by the spatial filtering provided by the second transducer so as to generate a traveling wave having a selected wavelength. The system includes automatic frequency selection to compensate for position sensing errors due to changes in the velocity of propagation of elastic waves arising because of temperature effects on the delay medium.

Abstract: An acoustical deverberator for eliminating the reverberation from a sound gnal originating with a transient sound source in shallow water. The sound signal is received by a single hydrophone and autocorrelated to determine the time differences between the direct signal and the bottom surface reflected signals. Together with the surface and bottom reflection coefficients and known depths of the hydrophone and water, the time differences are used to determine corrections which are applied to the received sound signal. The result is a clean sound signal free from interfering reverberation.

Abstract: An improved position determining device using a delay line with energy absorptive terminations at the ends thereof and having a driver transducer coupled to the delay line for producing a traveling wave on the line and a first receiver transducer coupled to the delay line at the distance to be determined. A second receiver transducer, also coupled to the delay line, is displaced from the first receiver transducer by a distance preferably substantially equal to one-quarter wavelength of the traveling wave signal. Each of the receiver transducers detects the direct traveling wave signal from the driver transducer and a traveling wave signal component which is reflected from an end termination. The detected signals from the second receiver transducer are phase-shifted by a 90.degree. phase lag and the phase-shifted signals are combined with the signals detected by the first receiver transducer, whereby the reflected signal components in the combined output signal are effectively eliminated.

Abstract: A moving sound source identifying system wherein a correlation function signal between two sound signals derived respectively from two microphones arranged apart from each other on the ground for respectively receiving sounds which are simultaneously emitted by a sound source is used for identifying whether the sound source is moving or stationary and whether it is flying or moving on the ground, by means of discriminating the variation of respective times whereat maximum or minimum levels of the correlation function signal appear, which variation is caused in accordance with the angle of elevation of the sound source. Continuously obtained results of the identification are utilized for classifying sound sources, removing the noise disturbance and automatically pursuing the sound source.

Abstract: 1. A system for detecting in bearing a source of sound in a predetermined plane and for measuring the frequency of said sound comprising in combination: two hydrophone dipoles sustantially arranged in said plane, each having at least two hydrophones, the axis of said dipoles being at right angles to each other said hydrophones receiving said sound and providing output signals these hydrophones having respective axes perpendicular to said plane; means for detecting the respective phase shifts between said output signals of the same dipole and providing phase shift indicating signals; and display means having two inputs for receiving respectively said phase shift indicating signals.

Abstract: A secure sonar communication system for transmitting and receiving intellnce signals within an aqueous medium comprising in combination means for generating an electrical pseudo random noise signal within a predetermined bandwidth, means connected to said pseudo random noise generating means for selectively driving same at one of a plurality of predetermined frequencies, keying oscillator means adapted to selectively produce an output of one of a plurality of predetermined frequency signals, a balanced modulator means coupled to said pseudo random noise signal generating means and said keying oscillator means for mixing the output signals therefrom, bandpass filter means connected to the output of said balanced modulator means for passing the upper sideband thereof, means for receiving an electrical pseudo random noise signal, transducer means, said transducer means being capable of broadcasting acoustical energy upon excitation by the upper sideband from the aforesaid bandpass filter means and in proportion

Abstract: 6.

Abstract: 1. A system for locating a radiating source comprising a plurality of mutly spaced radiation detectors, first means for correlating the output of one of said detectors with the output of a second of said detectors, second means for correlating the output of the second of said detectors with the output of a third detector, means coupled to said first and second correlating means for separately integrating the outputs thereof to produce a pair of integrated signals, and means for delaying one of said integrated signals with respect to the other of said integrated signals, whereby the delay is indicative of the range of the source from the detectors when the maximum amplitude of the delayed integrated signal coincides with the maximum amplitude of the other integrated signal.

Abstract: A Doppler compensated PSK signal processor which receives a plurality of sages from a sensor array and decodes each message for further data processing. The signal processor compensates for the Doppler shift in the message frequency due to the velocity differential between the transmitting vehicle and the sensor array. The message is decoded for a valid identification code from which is derived a time mark related to a specified system time to provide range and direction information for the identified transmitting vehicle. The telemetry data in the message and the time mark are output to a data processing system on an interrupt basis to provide tracking and data analysis for the transmitting vehicle.

Abstract: Method and apparatus are provided for locating a towed float relative to the towing vessel. The method determines the range from at least two known spaced apart locations on the towing vessel to the float and determines the position of the float from the intersection of the at least two ranges. The apparatus includes a microwave transceiver selectably interconnectable with a plurality of microwave antennas at known spaced apart locations on a towing vessel, a microwave transponder on each float whose locations is to be determined, and suitable controller and/or computer means to calculate ranges and intersections of ranges.