Abstract: A system and method are provided for an adaptive filter that is especially useful for sonar signal processing. The beam outputs of a conventional beamformer are provided as inputs to adaptive notch filters in accord with the present invention. The outputs of the plurality of adaptive notch filters are applied to a standard cross correlation process. In each of the adaptive notch filters, the beam outputs are split into two paths and in one path are applied directly to a signal combiner. In the second path, the beam outputs are delayed. The delayed beam outputs are applied to an adaptive finite impulse response filter, the output of which is an estimate of the narrowband interference contained within the beam output. The narrowband interference is then suppressed in the signal combiner prior to application to the standard cross correlation process.

Abstract: Signals from microphones 1, 2 are first stored in memory circuits 4, 6 and then supplied to a cross-correlation arithmetic circuit 7, following which a cross-correlation operation is carried out and cross-correlation function values are calculated for each time difference. An evaluation function circuit 8 carries out addition processing of particular time intervals based on the cross-correlation function values and then searches for the maximum value to calculate time differences. Signals from the microphones 2, 3 are first stored in memory circuits 6, 5 and then supplied to a cross-correlation arithmetic circuit 9, following which a cross-correlation operation is carried out and cross-correlation function values are calculated for each time difference. An evaluation function circuit 10 carries out addition processing of particular time intervals based on the cross-correlation function values and then searches for the maximum value to calculate time differences.

Abstract: According to one aspect of the present invention an apparatus for multiple document detection includes an ultrasonic transmitter (14) for transmitting an ultrasonic signal (16). An ultrasonic receiver (20) receives the ultrasonic signal (17), after it passes through the at least one of the multiple documents (18). A phase comparator (24) compares the transmitted ultrasonic signal (16) and the received ultrasonic signal (17), and an amplitude measurement circuit (26) compares the received ultrasonic signal (17) to a reference. A microprocessor (32) compares an information signal (28) from the phase comparator (24) and an information signal (30) from the amplitude measurement circuit (26) to a predetermined threshold to determine if multiple documents are present.

Abstract: A method of determining the bearing of a source of a sonar signal comprising determining the phase of a cyclic variation of the output signal of a sonar detector having a directional characteristic which occurs as the orientation of the detector, and hence its characteristic, is rotated. In a preferred method the sonar detector output is spectrum analysed at each of a plurality of different orientations of the detector to provide for each orientation a signal representative of the amplitude of a component of the signal produced by the source of a chosen frequency. The signals so obtained are then arranged to form a time series of samples of said component as the orientation of the detector is rotated at a predetermined frequency and the time series used to analyse the spectrum of the signal defined by the time series and thereby determine the phase of the sinusoidal component of the signal defined by the time series at the predetermined frequency. Apparatus for carrying out the method is also disclosed.

Abstract: A method includes the steps of segment-wise detecting and bringing into coincidence signal waveforms for conversion into monotone and continuous trajectories for real-time pattern recognition, localization, and monitoring optical and acoustic signals. The method also determines transit-time differentials, wherein pre-programmed key signals are detected by signal sampling, data is correlated from the sampled signals, and pairs of signal combinations of given signal transit-time differentials from the coincidence of the detected signals are determined.

Abstract: The invention involves a computationally simple and fast method for aligning the phases of complex signals (real (in phase) and imaginary (quadrature) components) before performing a coherent (in phase components) or vector sum, thus achieving the high gains of in phase summations without pre-processing overhead to determine an optimum progression of phase shifts to enable in phase summations. The method of the invention for aligning the phases, without preprocessing to get an optimum set of phase shifts, uses the temporal relationship that exists in the phase angles of successive vectors that occur evenly spaced in time.

Abstract: A method and system for use in an air acoustic system for determining and using beamform factors for forming air acoustic beams approximating an optimum air acoustic beam for the directional transmission or reception of air acoustic energy by an air acoustic phased array system. Maximum and minimum dependent beamform factors of an optimum beam are determined from initial beamform factors and an initial parent population of chromosomes is generated, each chromosome including a gene corresponding to a dependent beamform factor and representing an initial candidate beam and subsequent parent populations are generated by cloning of the chromosomes of surviving populations. A child population is generated from a parent population by exchanging statistically selected pairs of genes of the parent population and generating a mutated population from the child population by mutating statistically selected genes of the child population.

Abstract: A system and method for finding the direction of a wave source using an array of sensors. The system includes a sensor array for measuring waves from the wave source, an approximate-direction finder for finding the approximate direction of the wave source in terms of a sensor pair from the sensors, a precise-direction finder for finding the precise direction of the wave source based on the approximate direction found, and a measurement qualification unit for evaluating the validity of the precise direction under a measurement criterion and discarding the measurements if the criterion is not met.

Abstract: A method of localizing signals utilizing auto-correlation functions and cross correlation functions includes: collecting data at a plurality of input channels; filtering the data collected from the plurality of input channels in order to identify a primary signal; identifying at least two lags and at least one reference lag in a function of the data; and estimating relative travel times of the data.

Abstract: The hybrid adaptive beamformer of the present invention includes a plurality of microphones for receiving sound energy from an external environment and for producing a plurality of microphone outputs from the sound energy. A processor produces a plurality of first order beams based on the microphone outputs. The processor determines an amount of reverberation in the external environment and adaptively produces a second order output beam taking into consideration the determined amount of reverberation. The processor may determine the amount of reverberation based on a comparison of the first order beams. The processor may produce the second order output beam by adaptively combining the plurality of first order beams, as further described below, or by adaptively combining the microphone outputs. The adaptation varies taking into consideration the determined amount of reverberation.

Abstract: A personal direction finding apparatus for determining the direction to be followed in order to reach a predetermined spot which includes a headset provided with two earphones and a circuit for generating a track error signal. The circuit includes a compass supported on the headset for outputting a heading signal corresponding to the heading of the direction of travel, a receiver for a position location and navigation system outputting a signal for the heading to be followed via one output, and a track error computing circuit.

Abstract: An underwater combination of a passive and an active acoustic mechanism is sed to detect and locate a surfaced or submerged object or target. The passive mechanism utilizes a pair of separated hydrophones to detect an object. The hydrophones are then followed by bandpass filters according to the frequency of interest and the outputs thereof correlated to locate the object. A positive correlation output indication initiates the active acoustic mechanism which then verifies the detection of an object by transmitting a pulse sonar. The output of a transducer responsive to the reflected pulse sonar is then analyzed to indicate whether the detected object is surfaced or submerged and whether the detected object is approaching, departing or stationary.

Abstract: A displacement measuring method that measures phase changes between a reference and a phase-shifted signal from -.infin. to .infin. degrees (limited by the size of counters) in precise incremental steps using a method referred to as Digital Phase Signature Comparison. Digital Phase Signature Comparison uses an n-bit digital pulse train synchronized to a reference signal to sample a binary phase-shifted signal of a known duty cycle. This n-bit sampling creates a unique phase signature which is stored in a memory device. One digital n-bit phase signature is created for each synchronized pulse train. Each stored phase signature is compared with the previous phase signature to determine whether the phase of the phase-shifted signal has changed, the magnitude of that change, and the direction of displacement. Error detection can protect against unknown phase signatures and phase signature transitions, thus ehminating accumulated or incident inaccuracies.

Abstract: A short baseline navigation system employs the real-time estimation of the positions of multiple cooperative targets. Each target replies with a unique stepped frequency sequence signal that covers the usable frequency band. A processor operates on reply signals received by elements on the tracking platform and develops a coarse time-difference-of-arrival estimate using an algorithm derived herein. The processor also estimates the Doppler shift of received signals, and determines a time-window (or gating) that eliminates the portions of the received signals corrupted by multipath interference. The relative phase differences between the received signals are then used in conjunction with the coarse time-difference-of-arrival estimates for a precise direction-of-arrival estimation.

Abstract: A sound enhancement system including a beamed linear array microphone system for the acoustic pickup of voice and music from substantial distances with a relatively narrow sound pickup beam and with the avoidance of acoustic feedback. The acceptance beam angle is relatively constant over the desired sound octaves. Response outside of the acceptance beam is relatively low. The system includes a microprocessor-controlled circuit for processing the signals from a multiplicity of microphone elements in the linear array for application to a loudspeaker.

Abstract: The present invention-relates to an ultrasonic array imaging system for focusing ultrasonic signals which are reflected from an object to be imaged and received by an array transducer. A digital focusing method and system in accordance with the present invention compensates for phase errors which are contained in digital data by using a quadrature sampling method in digital-processing and focusing of ultrasonic signals. Each of a plurality of delayed-time eliminators receive signals generated by quadrature sampling and removes delayed-time differences from signals. Each of phase compensators receives a digital signal in which a delayed-time difference is removed, and compensates the received digital signal for phase errors. An envelope detector is used to detect an envelope signal using the phase error compensated date.

Abstract: Methods and systems for beamforming are disclosed that include a signal processor that can dynamically determine the relative time delays between a plurality of frequency-dependent signals. The signal processor can adaptively generate a beam signal by aligning the plural frequency-dependent signals according to the relative time delays between the signals. The signal processor can store one frequency-dependent signal as a reference signal and can align the remaining frequency-dependent signals relative to this reference signal. One advantage of the signal processor is that it can align the plural frequency-dependent signals generated by an array of microphones that can be arranged in a linear, two dimensional or three dimensional array and located in a room environment.

Abstract: A process for locating a transmitter in which the signal is received by first and second receivers and then processed by respective analog to digital converters and filtered to yield first and second digital signals. There is relative motion between at least one of the receivers and the transmitter. A compression process local to the first receiver compresses the first digital signal. The result of the compression process is transmitted to a cross-correlation unit which is local to the second receiver and coupled also to receive the second digital signal. Locally to the first receiver, correction factors for the solution to the cross-correlation function are determined and transmitted to a correction unit at the second receiver site which applies the correction factors to the solution of the cross-correlation function. The location of the transmitter is determined based on time difference of arrival and frequency difference of arrival results output from the correction unit.

Abstract: A system for the instantaneous determination of the frequencies and angles of arrival of a plurality of simultaneously incoming signals. The system includes beam network matrix for receiving the simultaneously incoming signals, the matrix providing one or more superimposed output signal which includes phase information associated with the angles of arrival of the signals. The system uses a Fourier receiver which includes a sampler means for periodically producing a sample of the superimposed output signals and a frequency differentiator for differentiating the sample by frequency into a train of discrete waveforms. Each of the train of discrete waveforms is associated with one of the incoming signals and includes phase information associated with one of the incoming signals. The Fourier receiver further includes a mechanism for determining frequency which determines from one of the train of discrete waveforms the frequency of one of the incoming signals.

Abstract: The present invention is directed to provide an underwater detection system which can determine frequency components contained in echoes arriving from all azimuthal directions at high speed and enhance target discriminating capabilities by presenting such frequency components.The underwater detection system rotates a pair of ultrasonic receiving beams having a fixed phase angle difference, measures phase differences between two signals picked up by both ultrasonic receiving beams, determines carrier frequencies contained in target echoes from the phase differences, derives magnitudes and directions of moving velocities of targets from the carrier frequencies, and displays such target data in different colors. Furthermore, it provides such information as over-the-ground velocities of targets themselves upon compensating target velocity data with ship velocity data.

Abstract: A signal processor for obtaining frequency and bearing information of an ustical signal. Responsive to the acoustical signal, a multimode hydrophone generates a plurality of electrical signals which are combined to form a first omnidirectional signal and two spatially orthogonal directional signals. The directional signals are then combined to form a second omnidirectional signal. Additional circuitry is provided to analyze the two omnidirectional signals using the cross-spectral density function of the two omnidirectional signals to obtain said frequency and bearing information.

Abstract: An ultrasonic tracking system embodying the invention has an array of plural ultrasonic detectors at discrete locations, the plural detectors being responsive to an ultrasonic signal of frequency f emanating from a single remote transmitter to produce respective plural electronic signals corresponding to the ultrasonic signal as received at respective ones of the plural detectors, and a processor for determining from the plural electronic signals a direction of travel of the ultrasonic signal relative to the array of ultrasonic detectors. In order to provide range, a phase shift key encoder connected to the transmitter encodes every N cycles of the ultrasonic signal with one of a succession of encoder counts, while a phase shift key decoder coupled to receive an electronic signal from one of the plural detectors produces a new decoder count every N cycles of the electronic signal that are decodable.

Abstract: A transmitter (12) broadcasts a PN encoded message (16). A receiver (14) includes a SAW correlator (38) configured to autocorrelate with the PN sequence used in the broadcast signal. A preamble of the message (16) conveys two successive bits (18) that are each encoded with the PN sequence. After the correlator (38) has been preloaded with the PN sequence from the first bit (18), its non-correlation output exhibits reduced amplitude time sidelobes. A timing comparison circuit (60) compares a correlation signal (46) with a timing threshold (72). The timing threshold (72) is established at a very low level to minimize the influence of multipath. False triggering on noise is prevented by disabling the timing comparison circuit (60) until after the first bit (18). At this point in time the correlator (38) has been preloaded with its PN sequence, is again being loaded with its PN sequence, and outputs reduced amplitude time sidelobes.

Abstract: A transponder of an active digital sonar system identifies a multifrequency underwater activating sonar signal received from a remote sonar transmitter. The transponder includes a transducer that receives acoustic waves, including the activating sonar signal, and generates an analog electrical receipt signal. The analog electrical receipt signal is converted to a digital receipt signal and cross-correlated with a digital transmission signal pattern corresponding to the activating sonar signal. A relative peak in the cross-correlation value is indicative of the activating sonar signal having been received by the transponder. In response to identifying the activating sonar signal, the transponder transmits a responding multifrequency sonar signal.

Abstract: An object locating system, especially for use in locating a gaming ball in the game of football, utilizes a series of three sensors positioned on one side of a football playing field and a calibration source positioned on the other side. The calibration source emits an ultrasonic signal which is received by the sensors in order to provide a calibration signal. A ball marking unit is positionable on the field at a location of the ball and emits an ultrasonic signal which is received by the sensors and an RF signal which is received by the calibration source in order to turn the calibration source off. The sensors provide signals in which a processing unit calculates time delays by a time acquisition process in order to determine the position of the ball. In an alternate embodiment, the ball marking unit emits only an RF signal which is received by the sensors. The sensors again provide signals which are analyzed by the processing unit to determine delay between receipt of the signals at the sensors.

Abstract: A system for target detection and localization with an algorithm for performing target motion analysis (TMA) using data from a passive sonar array and which works directly with beam spectra to estimate the target track. The system determines when the coordinate trajectory of a hypothesized target aligns with the coordinate trajectory of an actual target and operates by forming long-term integrated spectral values from short-term values of frequency and angle coordinate values. The hypothesized target track that yields the maximum long-term integrated spectral value is used as the estimate of the true target track. A track generator is used to generate hypothesized target tracks for a search grid in the form of vectors that are clocked downward in a chain of latches. The latches are connected through computational elements, which are supplied with non-acoustic data, and RAMs to a summation pipeline, the RAMs being supplied with data from an array's sonar processor.

Abstract: A detection method and system utilizing silicon models of the traveling wave structure of the human cochlea to spatially and temporally locate a specific sound source in the presence of high noise pandemonium. The detection system combines two-dimensional stereausis representations, which are output by at least three VLSI binaural hearing chips, to generate a three-dimensional stereausis representation including both binaural and spectral information which is then used to locate the sound source.

Abstract: The present invention provides a method for on-line real-time processing of processing navigational data for determining the location of sensor and receiver points in a navigational network having a number of different types of devices. Observations from these devices are obtained using a coordinate system that follows appropriate nominal sailing lines. Outlying observations are discarded using w-statistics for the observations. Any correlated observations such as compass azimuths are uncorrelated. The uncorrelated observations are then sequentially processed in an extended sequential Kalman filter, which provides the best estimate of the station coordinates. These estimated coordinates are then used to determine the location of the source and receiver points.

Abstract: A leak detecting microphone inserted directly into fluid within a pipe includes a housing having a first end being inserted within the pipe and a second opposed end extending outside the pipe. A diaphragm is mounted within the first housing end and an acoustic transducer is coupled to the diaphragm for converting acoustical signals to electrical signals. A plurality of apertures are provided in the housing first end, the apertures located both above and below the diaphragm, whereby to equalize fluid pressure on either side of the diaphragm. A leak locating system and method are provided for locating fluid leaks within a pipe. A first microphone is installed within fluid in the pipe at a first selected location and sound is detected at the first location. A second microphone is installed within fluid in the pipe at a second selected location and sound is detected at the second location.

Abstract: A continuous wave ultrasonic tracking system using an ultrasonic transmitter acoustically radiating a continuous wave ultrasonic transmitted signal and an ultrasonic receiver detecting the transmitted signal as a received signal. The system mixes the transmitted and received signals to create an interference pattern characterized by interference fringes, counts the number of the fringes by which the pattern changes with respect to a fixed point and stores the number as a number of wavelengths of the displacement between the transmitter and receiver, interpolates a location of the fixed point between successive ones of the interference fringes as a fraction of a wavelength and stores the fraction of a wavelength and computing the displacement by combining the number of wavelengths and the fractional number of wavelengths.

Abstract: A method and to a sensor for determining the distance of sound generating targets, preferably wheeled or track-laying vehicles, from acoustic signals which are subjected to a Fourier transformation. In order to determine the target distance easily and reliably, it is provided that the acoustic signals received by an acoustic sensor at two successive points in time from a target that is at a distance r.sub.1 and r.sub.2, respectively, from the acoustic sensor are employed, after the Fourier transformation, for an evaluation of the phase difference in the sound spectrum which yields the difference between the distances of the target from the sensor at the two points in time, from which difference the target distance is then calculated according to the spherical wave model.

Abstract: An inspection apparatus utilizing a pulse compression technique is described which comprises a signal generator, a transmission/reception probe; first and second correlators and an adder. The signal generator generates a composite transmission signal consisting of signals Sap(t), Saq(t), Sbp(t) and Sbq(t) respectively based on a basic unit signal ga(t) and a sequence {p}, the signal ga(t) and a sequence {q}, a basic unit signal gb(t) and the sequence {p}, and the signal gb(t) and the sequence {q}, to the probe to transmit the composite transmission signal to a target. The first correlator performs a correlation operation of echo signals Rap(t), Raq(t), Rbp(t) and Rbq(t) corresponding to the signal Sap(t), Saq(t) and Sbq(t) by utilizing reference signals Ua(t) and Ub(t) based on the sequences to provide results Caap(t), Caaq(t), Cbbp(t) and Cbbq(t).

Abstract: A system separates unknown signals which have been combined together through unknown linear filters and for which observations at multiple sensors are made. In a two channel circuit with two inputs and two sensors, the reconstructed source signals are assumed to be decorrelated such that the cross-correlation between the reconstructed source signals is near zero. The transfer functions which represent the crosstalk processes are estimated. The output signals are detected and the transfer functions are recursively solved. A reconstruction filter is used to recover the original input signals.

Abstract: A passive acoustic target tracking system includes three microphones arrayed respectively at corners of an equilateral triangle for sensing acoustic energy emitted by a target, such as a heavy vehicle, and generating separate streams of analog signals representative of the acoustic energy sensed at the triangle corners. Hardware of the tracking system receives the separate streams of analog signals from the microphones and conditions and converts the separate streams of analog signals from analog to digital form and outputs the separate streams as digital signals. Software of the tracking system receives the separate streams of digital signals and provides the bearing to the target emitting the sensed acoustic energy. The software includes a minimum residual correlation algorithm and a two-state kalman filter algorithm.

Abstract: The source region of a volcanic tremor is determined by simultaneously detecting the tremor using seismometers installed at at least four separate points, obtaining correlation functions among pairs of the detected values, calculating at least three observation time lags corresponding to the maximal values of the correlation functions, and using the at least three observation time lags for determining the source region of the volcanic tremor.

Abstract: An apparatus and method for determining the location of a pipe leak detects the pipe leak sound at a first remote location and at a second remote location, and generates first and second signals indicative of the sound. A time lay between the first and second signals is calculated at each of a plurality of frequencies. Integer multiplies of an associated period are added to each time lag to form a plurality of potential time delays at each of the plurality of frequencies. The plurality of potential time delays at all of the plurality of frequencies are stored in a memory. The time delay value which occurs most frequently is selected from the memory and is utilized to calculate the location of the sound source relative to the first and second locations. The invention can also be employed to determined the location of a sound source other than a pipe leak.

Abstract: A detector system having a channel for comparing the peak amplitude of at least one of two electrical signals, produced at the output of two spaced geophones, against an amplitude threshold, to produce an indication of a moving object when this threshold is exceeded. To reduce the number of false indications, the system includes a parallel channel for measuring the phase difference between the two signals, and a processing circuit responsive to both channels, to ensure that indication is allowed only when the measured phase difference changes sense. The parallel channel includes four flip-flops each to measure the phase difference and the outputs of these flip-flops are added together, to produce a phase dependent signal for controlling the processing circuit. Further discrimination is provided by timing the phase transition, a time gate being used to inhibit indication when the phase transition does not occur within prescribed time limits.

Abstract: A method for determining the motion of a target in underwater acoustics by means of an antenna with misaligned sensors (C.sub.1, C.sub.2.sup.P, C.sub.3) provided with a central sensor C.sub.2.sup.P. It consists in estimating the characteristics of velocity (V.sub.x, V.sub.y) and position of the target x(t*), y(t*) relatively to the antenna by means of a likelihood maximum estimator taking account of the differences in propagation times measured between the wave fronts transmitted by the target and reaching the sensors. The motion estimator is initialized by means of an initial state vector X determined on the basis of the values of the azimuths of the target perceived from the mid-points of each pair of sensors, during a determined number of measurements staggered in time. The action of the state vector X takes place in taking account of the value of the elevation of the target with respect to the antenna.

Abstract: A passive acoustic detector including a line hydrophone and apparatus coud thereto operable to utilize the energy sensed by the elements of the hydrophone during passive listening to effect scanning in depression-elevation by delaying for directivity and then combining acoustic energies sensed by the hydrophone elements and recording the combined energies on an x-y strip recorder for enhanced signal-to-noise ratio.

Abstract: Apparatus located aboard a platform situated in an acoustic environment for racking a moving body when the body is proximate to the platform. The apparatus includes a selected number of acoustic sensor elements at selected locations around the platform, each of the elements for detecting acoustic information arriving at its selected location. The apparatus further includes signal conditioners coupled to the sensor elements, a given one of the signal conditioners providing a conditioned signal representing acoustic information which is emitted by the moving body when the body is proximate to the platform, and which arrives at the location of the acoustic sensor element to which the given signal conditioner is coupled.

Abstract: Apparatus and method for transmitting and receiving hydroacoustic pulses used to determine the spatial separations between pairs of such apparatus. According to a preferred embodiment, the apparatus transmits hydroacoustic pulses having a selected shape and frequency at specific times and also determines the time of arrival of received hydroacoustic pulses having a known shape and carrier frequency. Included is a transducer for converting the hydroacoustic energy received from a body of water into electrical energy and for converting electric pulses into hydroacoustic pulses which are then coupled into the body of water. Electric pulses having a selected shape and carrier frequency are digitally synthesized in response to a count comparator.

Abstract: A stationary probability integrator system for facilitating spectral anals of detected signals by suppressing random frequency background noise, such as ocean disturbances and marine life, and by enhancing spectral signatures of discrete sound sources, such as generated by submarines in water. A raw 0 to 100 Hertz frequency spectrum of noise and spectral signature from a frequency analyzer having 500 increments or elements is divided into ten assemblies of 50 elements per ensemble. The ensemble averages, which are the average simultaneous energy levels of all elements in respective ensembles, of each sample is negatively combined with the energy level of each element of the corresponding ensemble of the next consecutive raw sample. Each combination and the cumulative algebraic sum of each combination is then displayed in the same frequency spectrum as the samples.

Abstract: Apparatus and method for sonar or radar target tracking. Digital apparatus nd techniques are employed. A variable delay is used for beam steering.

Abstract: A passive sonar bearing tracker having spaced arrays wherein the target bing is a function of the electrical phase angle of the signal between the arrays. Confidence in the bearing estimate is increased in spite of the relatively narrow bandwidth of the signal and a low signal-to-noise ratio by sequentially bandpass frequency filtering each very narrow component of the narrowband signal, computing the phase difference between respective filter pairs, accumulating the phase differences over a selected time period and displaying the phase difference calibrated as a bearing. In a second embodiment the individual differences are weighed according to the magnitude of the frequency signal at the associated very narrow band.

Abstract: Signal phase delay may be accurately measured by transmitting a pseudo-random noise coded reference signal, deriving in-phase and quadrature components of the received coded signal and then separately decoding the in-phase and quadrature components. This technique effectively compresses the transmitted signal pulse to a very narrow width (thereby simplifying discrimination of separate pulses with similar arrival times) while magnifying the pulse amplitude (thereby enhancing the signal to noise ratio).

Abstract: An improved spatial filtering system includes a plurality of tracker modules for isolating selected signals from an array of signal data values collected from a signal environment by a plurality of receiver elements and stored in a residual signal storage element. Each tracker module includes a generating module for generating, from the array of signal data values, estimated contributions of a selected signal at each of the plurality of receiver elements. Each tracker module also includes an output signal estimation module, connected to the generating module, for determining, based on the estimated contributions, an output signal that is representative of the selected signal.

Abstract: In a method for locating sound sources, signals from three aligned sensors are processed by correlating the signals of the central sensor with those of the outer sensors and then by processing the correlation signals so as to maximize the sum of these signals, thus making it possible to identify the position of the noise sources more efficiently.

Abstract: A passive detection technique is based on correlation characteristics of split beam inputs with given relative rates between a detection sensor platform and a target source. The correlation coefficient (10, 12) between two phase offset beams is first computed and, at the same time, the relative angular position between the sensor line-of-sight and the target source are estimated (14) to establish the pattern matching function. The correlation operations are carried out for both real and imaginary channels with a four quadrant multiplier (20, 22, 24, and 26). The outputs of the multiplier are summed (28, 30) to obtain real and imaginary channel outputs which are smoothed over a period of time in integrators (32, 34) to eliminate undesirable correlation patterns. The outputs of the integrators are independently thresholded (36, 40) and square summed (38, 42 and 44) and then threshold (46) to provide an indication of target detection.

Abstract: A method is provided for detecting and localizing acoustic sources. Acous signals are transmitted by a sonobuoy and return signals are received. Electrical signals, corresponding to the received return signals, are multiplexed and transmitted. The transmitted signals are received by a receiver which is separated from the transmitter. The receiver applies the received signal to a demultiplexer which is separate from the the receiver. The demultiplexer demultiplexes the applied signals to provide electrical signals to the cardioid beamformer representative of the sonar return signals.

Abstract: By incorporating a Global Positioning System (GPS) receiver into the electronics of an active or passive sonobuoy for determining a geoposition of each sonobuoy comprising an array of sonobuoys or a sonobuoy field, the position of each sonobuoy can be ascertained as the original position of the line of sonobuoys forming the array changes due to wind, sea state and currents. The GPS geoposition of the individual sonobuoys is transmitted to as receiving vehicle along with the acoustic signal obtained by the sonobuoy sensor. Utilizing an onboard computer, the receiving vehicle can compute a synthesized coherent array position. The military P(Y) code transmitted by the GPS satellites is utilized to determine the geoposition of the sonobuoy relative to the other sonobuoys to a degree of accuracy of 2 to 3 meters.