Abstract: A multi-dimensional acoustic, data processing and display system arranges acoustic data in a three-dimensional matrix. The three-dimensional matrix is compressed using singular value decomposition into singular vectors and singular values. A historical database is created and maintained and is also concatenated with the three-dimensional data. This database allows reverberation and noise to be diminished and other, weaker features in the data to be enhanced. Once the data is compressed, the data can be analyzed efficiently. The singular vectors are partitioned into one or more groups on the basis of their singular values or other criteria. Certain of the compressed data elements are enhanced or diminished by modifying the singular values within each of the groups of singular vectors. Selected singular vectors are processed further by other techniques for further enhancement, detection, isolation, feature extraction and classification.

Abstract: The transit time of acoustic waves between a generator and a receiver positioned across a fluid chamber is determined by generating acoustic waves using a self-purging pneumatic sound generator, a transducer adjacent the outlet of the sound generator, and a receiving transducer positioned away from the sound generator outlet so that the acoustic waves received by the receiving transducer pass through a portion of the fluid. The electrical signals generated by the transmitting transducer and the receiving transducer are processed to obtain the impulse response of these electrical signals, and the point of maximum value is determined. This point of maximum value corresponds to the arrival time of the acoustic waves at the receiving location. The transit time determination may be used to calculate the fluid temperature or other parameters.

Abstract: A normalizer based on a Least Mean Square (LMS) adaptive algorithm configured to provide effective normalization when the background noise is locally non-stationary and when the target may be subject to time spread of unknown extent. The LMS algorithm used in the normalizer includes an adaptive filter in both the primary and reference inputs as a means of adapting to variations in both the signal and noise statistics. The LMS algorithm is implemented on the logarithm of the data, so that the difference minimized in the LMS structure drives the ratio of the signal power to noise power to a constant value. The algorithm can be used as a range normalizer by running it over range in each doppler bin, or as a frequency normalizer by operating across doppler in each range bin. By continually adapting to the statistics present in the data, the normalizer more effectively deals with the variations in the noise and signal statistics.

Abstract: The uncertainty inherent in high-resolution acoustic pulse-echo distance measuring systems which depend on threshold detection is overcome by transmitting a multi-cycle shot of acoustic energy having a sharply peaked amplitude profile, and locating the peak amplitude of a received echo. The peaked amplitude is achieved by timing the duration of energization of a transducer producing the shot so that energization is terminated before the amplitude of oscillation of the transducer has reached a maximum. This produces a shot which has a definite largest cycle, which should in turn produce an echo having a definite largest cycle.

Abstract: An improved sonar signal processor and display combining the use of both coherent and incoherent signal processors. In addition to a conventionally used matched filter detection processor, an incoherent signal processor comprising a cross-range energy filter and a down-range energy filter is used. The cross-range energy filter detects objects characterized by a narrow bearing response; whereas the down-range energy filter detects objects characterized by a narrow range response. The detection events resulting from the incoherent signal processor are displayed in a subdued color to prevent distraction from the primary display events and to reduce the false alarm rate by allowing the sonar operator to view events in the context of natural boundaries.

Abstract: A device is provided for processing an echo received by an array of N receiving elements from a target at range R ensonified by an LFM signal of bandwidth B transmitted for a duration T. The device receives each elements output f.sub.n (t) over the elements total receiving time and selects time window element outputs f'.sub.n (t), which are discrete portions of f.sub.n (t), each time window extending from an arbitrary initial time T.sub.0 to time T.sub.f and is spaced from T.sub.0 no more than T and, if there is a target within the window, an echo is received at time T.sub.n. Further the device produces element frequency difference outputs g.sub.n (t) from the frequency difference between a replica of at least a portion of the transmitted LFM signal and the time window element outputs f'.sub.n (t), the outputs g.sub.n (t) being tones with frequencies directly proportional to the time T.sub.n of the target from the time T.sub.0 so that the target range R=(c/2)(T.sub.0 +T.sub.n)+.DELTA.R.sub.

Abstract: A multi-dimensional acoustic data processing and display system arranges acoustic data in a three-dimensional matrix. The three-dimensional matrix is compressed using singular value decomposition into singular vectors and singular values. A historical database is created and maintained and is also concatenated with the three-dimensional data. This database allows reverberation and noise to be diminished and other, weaker features in the data to be enhanced. Once the data is compressed, the data can be analyzed efficiently. The singular vectors are partitioned into one or more groups on the basis of their singular values or other criteria. Certain of the compressed data elements are enhanced or diminished by modifying the singular values within each of the groups of singular vectors. Selected singular vectors are processed further by other techniques for further enhancement, detection, isolation, feature extraction and classification.

Abstract: False target (reverberation, clutter, etc.) detection is suppressed in an echo ranging system (sonar or radar) in which target velocity and range are measured using a composite Doppler invariant-like signal having at least two segments, such as are present in a "rooftop" or "vee" HFM signal, such composite signal having an ambiguity function with two or more ridge lines of different slopes that intersect along the zero-velocity time axis. A bank of matched filters provides a distribution of outputs which has an ambiguity function-like character with intersecting pairs of ridge lines, the intersecting points of said pairs characterizing the range and velocity of the echo returns. This distribution is adjusted so that the intersecting ridge lines of each pair have equal and opposite slopes with respect to the time axis. In particular, fixed reverberators, which would have ridge lines intersecting on the zero-velocity time axis, would be symmetrical about this axis.

Abstract: Target velocity and range are measured with high resolution in an echo ranging system (sonar or radar) using composite Doppler invariant signals consisting of at least two segments, such as "rooftop" or "vee" HFM signals, such composite signals having ambiguity functions that intersect along the zero-velocity time axis with ridge lines slanted in different directions. A single correlator is used for each segment wherein returns from the target are correlated with replicas of each segment of the composite signal to separately transform the Doppler frequency shifts of the target return into outputs whose time relationship provides a frame of reference for high resolution measurement of the velocity of the target. The time relationship measurement is implemented by a set of tapped delay lines and coherent summers which output a coherent correlation-like detection peak in a bin which corresponds to the target's velocity.

Abstract: A system and method for bottom tracking in a sonar system. The present invention provides for convolving the received signal with the second derivative, or an approximation thereof, of the matched transmitted pulse. In another aspect of the invention, the received signal is convolved with the matching transmitter pulse and the result is evaluated by summing the differences between a central peak and its neighboring left and right values. The filtering of the present invention removes the effect of water absorption on signal amplitude. The invention also includes compensating for spreading loss in the received signal.

Abstract: The invention provides a method of and apparatus for determining if a newly reported target is correlatable with target tracks already stored in a data base. Correlation is effected in stages rejecting uncorrelatable stored target tracks and accepting closely correlated target tracks and includes decision applying means for accepting a stored target track as a correlated track only under stringent conditions.

Abstract: Doppler insensitive waveforms, such as portions of hyperbolas having the same asymptotes, may be used to modulate pulses or sub-pulses of energy for probing a determined environment so that when the modulated energy is transmitted and received, the received energy may be processed, such as by correlation with the transmitted energy without regard to any Doppler frequency shift between the transmitted energy and the received energy. The Doppler frequency shift may have been imparted by reflection of the transmitted energy from an object having a relative radial velocity with respect to a sensor of the received energy. Also included are apparatus for processing received energy by correlation with transmitted energy, a method for modulating energy that may be transmitted and a method for detecting an object without regard to Doppler frequency shift or relative radial velocity.

Abstract: An ultrasonic flaw inspecting apparatus is provided in which the transmission signals comprising N number of the binary code sequences having sharp autocorrelation functions are input to an object to be inspected by a single transducer for transmission and the reflected signals are received by N number of transducers for reception. The N number of transducers for reception are connected and placed over each other so that the direction of respective polarization is inverted in terms of the time order of the binary code of the sequence.

Abstract: A method of active sonar detection of a stationary target in the water from board a moving vessel. A moving vessel having an active sonar system transmits a series of sonic pings out into the water. The transmitted series generates a corresponding series of reflections. Each of the reflections contains 1) acoustic reverberation and noise, 2) reflections from moving objects and 3) reflections from a stationary target. Each of the reflections in the series is digitized and stored in a matrix memory. The reflections are shifted in the matrix memory based upon how fast the vessel is travelling between successive pings. Each of the columns in the matrix memory are then summed such that the summation attenuates the acoustic reverberation and noise as well as the reflection from any moving objects and generates an indication of the stationary target.

Abstract: Ultrasonic thickness measurement of layers of paint on a substrate produces pulse echoes indicative of each layer interface. Several ultrasonic waveforms are averaged in a digital oscilloscope and the resultant waveform is analyzed by a computer programmed to recognize wave forms resembling pulse echoes, compare such waveforms to stored reference waveform characteristics, and selecting the waveform having the best fit to the reference. Each selected pulse echo is graded based on amplitude, peak separation, peak symmetry, and spacing from a previous echo to determine the quality of the waveform. Layer thickness is calculated from the spacing between pulse echoes and the velocity of sound in the layer material.

Abstract: Apparatus and method for providing increased gains in detection and classcation of active sonar targets while concurrently preventing target cognizance of detection. Operation starts with transmission of a sequence of FM slides as subpulses alternately up slide, down slide, up slide, etc., while varying randomly the start frequency of each. Subpulse lengths short enough to avoid overlap of echoes from multiple major reflectors are used. Each slide is started at a randomized frequency. Just enough bandwidth is used on each slide to achieve the range resolution desired for searching. Considering only the individual subpulse bandwidth, subpulses are transmitted throughout the systems total bandwidth. Enough subpulses are transmitted to achieve the bandwidth/time product desired for searching.

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 vibratory, time variant, pseudorandom sonar system includes a computer controlled pseudorandom digital sweep frequency source, a digital/analog converter for changing the digital output of the source to an analog output and a power amplifier for amplifying the analog output to drive a vibrator or other suitable transducer for injecting corresponding sound waves into a body of water for target detection. A memory is provided for storing the source's digitized output.A target reflects the sound waves for detection by 3 arbitrary non-colinear hydrophones which outputs a plurality of analog signals corresponding to the reflected sound waves to a plurality of channels. Each channel includes a preamplifier and an analog/digital converter for digitizing the analog electrical signals for storage in the memory. A computer controlled timer determines the time lapse between the injection of the source signal and detection of the reflected source signal by each hydrophone of the hydrophone array, for storage in memory.

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 continuous-transmission frequency-modulated (CTFM) scan converted sonar with improved capability for detecting swimmers, miniature submarines and other small intruders in harbors and inlets, and adjacent offshore structures. The system is microprocessor based and menu driven from an operator interactive touch screen. The system utilizes a fast fourier transform (FFT) based frequency analyzer for range discrimination. An area moving target indicator (AMTI) portion of the system cancels echo returns from stationary objects that otherwise mask the echo return of the moving targets. The AMTI causes the system to survey the search area for a number of consecutive scans and store the data. On successive scans, only target information that differs from the stored target map is displayed, thereby reducing clutter caused by surrounding terrain.

Abstract: A digital complex correlator for correlating in-phase and quadrature components of data samples by shearing the in-phase and quadrature data pairs by a predetermined multiple of the noise in the correlation window under analysis. The sheared data is multiplied by a variable factor generated in accordance with the shearing threshold and the number of samples in the window. The variable factor is generated to maximize the precision in the data while avoiding overflows in the complex multiplication and accumulation of the correlation process.

Abstract: An apparatus (10) for determining while drilling in the earth with a drill bit (12) the positions of seismic wave reflecting geologic formations (15, 17) has seismic wave sensors (A, B) positioned in the earth near its surface (42). The sensors (A, B) are disposed at known positions with respect to the borehole. The drill bit (12) generates the seismic waves. The sensors (A, B) receive the seismic waves both directly and by reflection from the geologic formations (15, 17). Adaptive filters (20, 26) are connected to each of the sensors (A, B). A summing circuit (34) receives outputs from the adaptive filters (20, 26). The converged impulse responses of the adaptive filters provide information about the amplitude of the reflected waves and their arrival times at the surface, thus allowing detection of the reflecting horizons and their location and physical characteristics.

Abstract: A receiver for active sonar systems comprises two fundamentally different detection processes operating simultaneously with the output of each detection process being combined by a computer utilizing a computer-aided detection algorithm. One detection processor is a segmented replica correlator (SRC) and the other detection processor is a polarity coincidence correlator (PCC). Each detection processor provides to the active computer-aided detection algorithm a list of ranges and bearings of a relatively small number of detection events. The computer algorithm operates on these events to compare events from the current ping and the previous ping for each of the processors.

Abstract: Apparatus for mapping moving objects by determining the cross-correlation function between two digitally sampled ultrasound A-line signals comprises a plurality of fractional step delay (FSD) digital interpolation filters which estimate the value of one of said input signals at intervals between said samples and a plurality of one-bit correlation circuits each of which determines the correlation between the first signal and the output of one of said interpolation filters.

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: Outputs of a linear phased array antenna can be employed for emitter field sorting, i.e., providing an indication of the frequency and angle of arrival of signals from a plurality of radiation sources, through the use of a two-dimensional optical processor that does not require a mechanism for correcting for acoustic spreading in a multi-channel Bragg cell. In effect, the multi-channel array of transducers of a Bragg cell forms a composite N-channel transducer the width of which is N times the spacing between channels. For a CW radiation source, the signal received by each array element undergoes an incremental phase shift associated with the tilt of the phase front across the array. When these signals are used to drive respectively adjacent transducers of a multi-channel Bragg cell, the acoustic effect within the bulk is equivalent to that of driving a large composite transducer with a constant frequency signal.

Abstract: A data analysis system accepts time related data samples which are develo from sets of common wavefronts incident upon a plurality of sensors. The data samples are converted from analog-to-digital form and the Fourier transforms relative to the frequency components are generated. The frequency components of the Fourier transforms are in turn cross-correlated for developing matrices of all possible correlations for each frequency component and then the matrices are integrated over a determinable time period. The resultant integrated matrices are compared with signals representative of an incident plane wave power as a function of its angles of arrival at a sensor array and of its frequency, producing output signals of relative strength indicative of the direction of the origin of the data samples.

Abstract: A method of and apparatus for carrying out machine vision of an object for obtaining object data therefrom in which the object is illuminated by frequency swept ultrasonic stress wave energy from a transmitting and receiving transducer array, or by light energy from a source, reflected signals are received respectively by the array and an optical-electronic camera, respective images in terms of the data contained in these received signals are fed to a processor in which the data is analysed to make use of the best data derived from both sources of illumination and the resulting data compared with reference data to provide stimuli controlling a reject device and/or positional adjustment devices directing the array and/or the camera.

Abstract: The invention concerns an application of linear system parameter estimation techniques to finite amplitude sonar devices, to extract fine grained angular position information about echo sources. The invention makes use of the fact that the waveform return by a reflecting object within the sonar's beam varies according to its relative angular position from the receiver, and a discovery that this variation may be fit to a linear system model using autoregressive estimation theory to extract the nature of the variation. In all cases, the information is extracted without the mechanical or electrical steering of the sonar transmitting beam.

Abstract: A digital pulse compression filter for use in a radar or sonar transmitting and receiving unit to process sampled and digitized signals. The sampling frequency (f.sub.s) is equal to about four times the center frequency (f.sub.o) and greater than about twice the bandwidth (.DELTA.f) of these signals. The pulse compression filter (5) comprises a time correlation circuit (7) supplied on the one hand with the sampled and digitized signals and on the other hand with signals representing a replica of the radar or sonar transmitter pulse, whereby one of the two types of signals supplied to the correlation circuit (7) is correlated with the orthogonal components of the other type of signals supplied to the correlation circuit (7) to obtain the orthogonal components of the compressed pulse.

Abstract: A multibeam acoustic apparatus utilizing a linear array of hydrophone elements in a sonar system includes a cascaded ladder capacitance-inductance network for coupling electrical signals to and from the individual hydrophone elements. The hydrophone elements are connected in series and the natural capacitance of these elements provides the capacitive characteristics of the network. Shunt inductors supply the inductance characteristics and provide a phase characteristic inversely related to frequency. Variable cumulative phase delays are provided for signals applied to successive hydrophone elements whereby a sonar beam is formed in a direction determined by the frequency of the exciting signal.

Abstract: A bistatic sonar employing LMS adaptive spatial prediction is used to process against surface reverberation from the convergence zone (CZ). Hydrophones spatially separated from the primary array are used as references. The critical behavior exploited by the invention is that since the reverberation may be viewed as an extended source for the reverberation, the correlation drops off with separation between the reference and primary sensors, while it stays a constant for the plane wave target return. The reverberation is non-stationary, functionally dependent on the signal (even though the back scatter is statistically uncorrelated with the signal), and spatially extended over the sector of the CZ annulus cut out by the transmitter azimuth beamwidth. The detection of the target is based on the sudden appearance of one strong target point source within a densely packed region of weak point sources that have been constantly present and whose sum is much larger than the target.

Abstract: A forward look sonar system in which speed and direction of a sonar platform is obtained. Each acoustic transmission towards the target area over which the platform is traveling is comprised of a plurality of frequencies. A plurality of receiver beams is formed and each individual beam from one transmission is cross-correlated with its corresponding beam from a selected subsequent transmission to derive a delay value. The later received signal for each beam, for each frequency is divided into a plurality of small segments each of which is cross-correlated with a portion of the first return signal corresponding to the same frequency and beam. The cross-correlation functions for the plurality of frequencies for each particular segment are added together to obtain a more precise delay value. The correlation functions for each of the beams are added together and compared to derive a value for platform direction in the intercomparison period and the delay values are utilized to derive a velocity indication.

Abstract: A method for evaluating echo signals transmitted and received by an ultrasonic transducer in a sensor of a movable mechanical element, such as an arm of an industrial robot, has the steps of receiving and storing the arriving echo signals in chronological sequence in a memory, the chronological sequence of the signal being converted into a corresponding sequence of memory positions, with successive sequences of echo signals of successive transmit pulses being stored in the same sequences of the memory positions. Integration of the echo signals of the successive sequences stored in the memory positions are undertaken such that the local shift of the ultrasonic transducer disposed on the moveable element which occurs between respective transmit pulses is compensated relative to chronologically adjacent pulses and the pulses reflected from a target are more easily identified.

Abstract: The disclosed invention is a method of seismic exploration using non-impulsive vibratory sources activated by filtered stationary, Gaussian codes. The method adds a distortion-free quality to the full-waveform seismic records.

Abstract: The disclosed invention is a method of seismic exploration using non-impulsive vibratory sources activated by stationary, Gaussian codes in urban areas. The method adds a distortion-free quality to the full-waveform seismic records.

Abstract: The disclosed invention is a method of seismic exploration using non-impulsive vibratory sources activated by stationary, Gaussian codes in a wellbore environment. The method adds a distortion-free quality to the full-waveform seismic records.

Abstract: An apparatus for the scanning of objects by means of ultrasound echography, comprising a mosaic (10) of ultrasound transducers which is connected to a transmitter stage (20) and a receiver stage (30) for the reception and processing of the ultrasound echos corresponding to the obstacles encountered by the transmitted signals in their direction of propagation, and also comprising a display stage (40). The transducers of the mosaic (10) are grouped in 2.sup.n subwindows in which a non-corrected echogram of an area of the objects scanned is formed. The receiver stage (30) comprises a device for determining correction delays to be applied to delay devices (61 . . . 68), said device comprising 2.sup.n -1 intercorrelation circuits (101,102, etc.) which operate on the basis of n successive divide-by-two operations of the aperture of the mosaic (10).

Abstract: A method is disclosed for determining if sign-clipped variations of full-waveform traces can be used in subsequent cross-correlation processing without undue hardship. In accordance with one aspect, the present invention examines skewness of the amplitude spectrum of the full waveform. If the former significantly differs from conventional Gaussian distribution over the frequency range of interest, i.e., the amplitude spectrum is non-Gaussian, sign-clipped versions thereof can be used in subsequent cross-correlation processing without undue loss in processing accuracy. In another aspect, the present invention is used to edit a series of traces, one at a time, gathered by a large multichannel collection system. In this aspect, the different spectral noise estimates, including cross-correlation estimates generated from sign-clipped versions of the full-waveform traces, are advantageously used.

Abstract: The disclosed invention is a method of seismic exploration using non-impulsive vibratory sources activated by stationary, Gaussian codes. The method has the channel-capacity economy of sign-bit recording and the distortion-free quality of full-waveform seismic records, even through zero memory, non-linear representations ("ZNL's") are employed either during the collection or the processing steps that produce such final records. As a result, stratigraphic facies can be both economically and surprisingly indicated.

Abstract: A range profile classifier wherein targets are identified based on the sequences of their received range profiles. Individual looks at a target are taken and it is assumed that the aspect angle of observation changes by no more than a predetermined amount. Correlations are made with reference data, which correlations are then summed recursively according to preselected restrictive criteria to obtain the most likely sequence corresponding to the target for which reference data is stored in the range profile target classifier.

Abstract: A detection system for imaging by sonar or radar signals. The system associates diversified transmissions with an interferometric base. This base provides an angular channel formation means and each signal formed in this way is processed by matched filtering in a circuit containing copy signals characterizing the space coloring obtained by the diversified transmission means. The invention is particularly applicable to side or front looking detection sonars.

Abstract: A bidimensional imaging system by echoes including a transmitting array and a receiving array. The transmitting array includes a row of transmitters (E.sub.1, E.sub.2, . . . , E.sub.i, E.sub.N) parallel to a direction Oz and the receiving array includes a row of receivers in a direction Ox. All the transmitters simultaneously transmit signals with different codes. The signals received are demodulated and the real and imaginary components of these signals are applied to two multiplexing circuits (61.1, 61.2). After modulation the multiplexed signals are applied to a Fourier transformation circuit (63), which sequentially supplies reception channels V.sub.k (.theta..sub.k) for the direction referenced by angle .theta..sub.k and which are stored in memories (66.1, 66.2). Other memories (70.1, 70.2) contain signals S.sub.i (.phi..sub.i) transmitted in an angular direction referenced by .phi..sub.i. The two pairs of memories (66.1, 66.2 and 70.1, 70.

Abstract: A sonar transceiver system and method includes an oscillator and programmable divider which are arranged to cause a transmitting transducer to transmit a plurality of four consecutive closely spaced tones in the manner of a pseudo-chirp. The receiver includes hard limiting means for converting received echo signals to binary signals and tone correlation and detection means including a shift register which compares samples of the binary received signal with a sample of a sine wave as hard limited which is carried on a storage register. A series of exclusive-OR comparator circuits effect the comparison and produce output signals of a desired magnitude when correlations are found. Switching means responsive to detection of the first of the transmitted tones causes the programming means to vary the divisors of the programmable divider to produce clock pulses of varying frequency to the shift register for the time and in the order of the transmitted tones.

Abstract: A sonar system for the detection of signals reflected from a sloping ocean bed in which a sample of the transmitted signal is modified to correspond to the received signal as modified by the sea bottom before both signals are applied to a correlation detector. Modification of the transmitted signal sample is provided by summing incrementally delayed portions of the transmitted signal sample.

Abstract: A system for detection by an echo containing transmission and reception sources for detection by acoustic waves in particular. A circular base with N columns T.sub.1, T.sub.2, -T.sub.i,-T.sub.N of electroacoustic transducers. To each column such as T.sub.i corresponds a transmission at the frequency f.sub.i. A switch makes it possible to change from transmission to reception. The signals received are applied to a channel forming device. For each channel such as V.sub.k the signals are filtered at frequencies f.sub.1, f.sub.2, -f.sub.N, which are applied to time offset circuits taking into account the base geometry and the channel direction. The signals obtained such as d.sub.i.k are applied to a display device which supplies the range, direction and speed of the targets detected. This is particularly applicable to underwater surveillance by sonar or radar.

Abstract: The invention concerns a method and apparatus for detecting Doppler-shifted waveforms in electrical signals. A replica is derived from the waveform prior to Doppler shift and stored in a storage device as a non-uniform profile having progressively increasing distortion along its length. The replica storage device is connected non-uniformly to correlating means such that the correlated replica profile has a degree of uniform distortion varying with storage position simulating varying degrees of Doppler shift. The electrical signal is uniformly correlated with the replica while the replica storage position is varied. An output signal is generated indicating correlation variation. The electrical signal is repetitively sampled and a maximum correlation is detected when the waveform occurs in the electrical signal with a degree of Doppler shift matching that simmulated by the correlated replica. The invention also includes apparatus for performing the method.

Abstract: The disclosed invention is a method of seismic exploration using vibratory sources activated by stationary, Gaussian codes. The method has the channel-capacity economy of sign-bit recording, at both the sources and receivers, without the sacrifice of any desired seismic information in the final processed records. Even the relative amplitudes between traces may be recovered in the method.

Abstract: This invention is directed to improved pseudorandom noise velocimeters and methods therefor, using the Doppler effect, to enable the external measurement of the speed of a moving target within a fixed conveying medium. In accordance with a preferred embodiment of the present invention a continuous pseudorandom ultrasonic noise signal formed by a repetitive code C having n different elementary segments S is radiated. Correlation between a received echo and the delayed radiated signal is accomplished by proceeding successively for each elementary segment, using a different measuring band, for a period corresponding to the period of each segment. The correlation values thus obtained are then stored and thereafter a Doppler low frequency curve is reconstituted by regrouping the correlation values corresponding to the different elementary segments of the repetitive code.

Abstract: This invention generally relates to echo location or ranging systems in which the individual properties of targets or reflectors (such as range, bearing, elevation angle, relative velocity, impedance contrast, etc.) in a field of targets within some propagation medium are identified by the emission of signals into the propagation medium and processing of the detected reflections from the target field.