Abstract: A digital-to-analog converter (DAC) for converting a digital input word to an analog output signal includes a string DAC, a first interpolator and a second interpolator. The string DAC outputs a first voltage and a second voltage in response to M most significant bits of the digital input word. The first interpolator interpolates between the first and second voltages in response to middle Q least significant bits of the digital input word and provides a first interpolated voltage. The second interpolator interpolates between the first interpolated voltage and the second voltage in response to lower P least significant bits of the digital input word.

Abstract: An ultrasonic sensing system includes: an amplifier including an input and an output; and an n-level comparator, coupled to the output of the amplifier, to compare an adjustable threshold voltage to an output signal from the output of the amplifier. N is greater than or equal to 1. The system also includes a noise power estimator, coupled to an output of the n-level comparator, to generate a noise power signal indicative of noise power of an input signal at the input of the amplifier. The system further includes a time-varying threshold circuit, coupled to the noise power estimator and the n-level comparator, to adjust the adjustable threshold voltage based on the noise power signal.

Abstract: Provided are a sonar system, transducer assembly, and method for imaging an underwater environment. The sonar system may include a housing having a transducer array defining first and second rows of transducer elements positioned at a predetermined distance. The first row of transducer elements may include at least first and second transducer elements configured to convert sound energy into first and second sonar return data. The second row of transducer elements may include at least third and fourth transducer elements configured to convert sound energy into third and fourth sonar return data. A sonar signal processor may be configured to process the first and second sonar return data and third and fourth sonar return data to generate respective first and second array sonar return data corresponding to a plurality of first and second receive beams and generate 3D sonar return data by correlating the angles associated with the receive beams.

Abstract: A method for creating a composite cable having at least one advanced termination on at least one end. An advanced termination is added to an end of a short synthetic tensile strength member. The strength of the tensile strength member and termination is then tested. Once tested satisfactorily, the short cable is spiced onto a long cable of the same type using prior art splicing techniques. The union of the short cable and the long cable creates a “composite” cable having a advanced termination on at least one end. In most applications it is preferable to set the length of the short cable so that the interwoven splice will exist at a desired location.

Abstract: There is provided a power transmission device which includes an antenna receiving a reflected power from a power receiving device, a power detection unit detecting a value of the reflected power received by the antenna, a control circuit determining a power adjustment value in accordance with the value of the reflected power, a power adjustment unit to which the reflected power whose value is detected is input and which adjusts impedance in accordance with the power adjustment value determined by the control circuit, and a demodulation circuit to which the reflected power having the power adjustment value determined by the control circuit is input via the power adjustment unit having the adjusted impedance, and relates to a power feeding system including the power transmission device.

Abstract: The suppression of off-axis audio in an audio environment is provided. Off-axis audio may be considered audio that does not originate from a region of interest. The off-axis audio is suppressed by comparing a phase difference between signals from two microphones to a target slope of the phase difference between signals originating from the region of interest. The target slope can be adapted to allow the region of interest to move with the location of a human speaker such as a driver.

Abstract: A method of determining a focused output signal of a sensor array comprising a plurality of sensors, each sensor being operable to output a sensor output signal responsive to a measured quantity, the focused output signal being indicative of a calculated quantity at a focus point; the method comprising: receiving a respective measured sensor output signal from each of the sensors; computing the focused output signal by performing a focusing calculation with respect to the measured sensor signals; wherein the method further comprises determining a subset of mesh points of a set of predetermined mesh points, each mesh point having at least one pre-computed filter parameter associated with it; and wherein computing the focused output signal comprises performing an interpolation with respect to the subset of mesh points so as to obtain an interpolated focused output signal.

Abstract: A marine seismic exploration method and system comprised of continuous recording, self-contained ocean bottom pods characterized by low profile casings. An external bumper is provided to promote ocean bottom coupling and prevent fishing net entrapment. Pods are tethered together with flexible, non-rigid, non-conducting cable used to control pod deployment. Pods are deployed and retrieved from a boat deck configured to have a storage system and a handling system to attach pods to cable on-the-fly. The storage system is a juke box configuration of slots wherein individual pods are randomly stored in the slots to permit data extraction, charging, testing and synchronizing without opening the pods. A pod may include an inertial navigation system to determine ocean floor location and a rubidium clock for timing. The system includes mathematical gimballing. The cable may include shear couplings designed to automatically shear apart if a certain level of cable tension is reached.

Abstract: A bank of order statistic filters applied to a set of antenna or transducer beams are used to detect and determine the line-of-bearing to the source of transient RF (or other, e.g., acoustic) signals. By applying order statistic filters to signals received by a set of antenna or transducer beams, this system sets a detection threshold that is unaffected by transient signals, thereby allowing the detection of these transient signals. Knowing which antenna beam the transient signals are located within allows the determination of a line of bearing to the source of the transient signals.

Abstract: A system and method for passively estimating range and angle of a source are disclosed. The source may be any wave source including radio-frequency (RF), optical, acoustic or seismic sources. In some RF embodiments, the system includes a single aperture antenna to simultaneously receive RF signals from the RF source through a plurality of sub-apertures, and a signal processor to perform a proximity test using samples simultaneously collected from the sub-apertures to determine whether or not to calculate angle and range estimates to the source based on either a curved wavefront assumption or a planar wavefront assumption.

Abstract: The invention relates to a system and method for processing a signal being emitted from a target signal source 20 into a noisy environment, wherein said target signal source 20 is located in a target signal source direction &phgr;s with regard to the position of a transducer array 10, the method comprising the following steps: receiving, transforming and filtering said signal according to filter coefficients of a beamformer 30I, 30II in order to generate at least one beamformer output signal y′i(n), i=1 . . . N, the filter coefficients defining a desired predetermined filter characteristic of the beamformer; and generating a control signal t(n) representing said target signal source direction &phgr;s. It is the object of the invention to improve such a system and method in the way that clear signal reception is achieved for any target signal source direction &phgr;s with only a minimum of computational effort and memory capacity.

Abstract: An advantageous combination of preamplifier electronics and circuits for acoustic beam forming with ultrasound transducer arrays permits integration of the electronics and transducer(s) at close distances in a compact arrangement and is operable from an ultrasound imaging or measurement system using only a minimal number of connecting electric wires. To achieve dynamic focusing of the receive beam with a transducer array, an integrated electronic circuit mounted in close proximity to the transducer array provides preamplifiers for the individual elements and delay circuits that are automatically switched in a predetermined time sequence after transmission of an imaging pulse. When a high voltage pulse is transmitted via the cable, a breakthrough circuit connects the cable to the transducer for transmission of the ultrasound pulse, while in receive mode the low level signal on the transducer is amplified and fed as a higher level signal via the same cable to the imaging or measurement instrument.

Abstract: The invention in its preferred embodiment is applied to a spherical assembly of rows of transducer elements arranged in a uniform distribution of elements in each circular row, each row being at a different latitude. The beamforming is accomplished in two steps. First, vertically oriented fan-shaped left and right half beams are formed by a portion of the transducers in each selected row within an elliptical array of transducers. Two adjacent left and right half beams are formed per row. These beams are angularly spaced by the included angle of two adjacent transducers of that row. By a process of interpolation of signals received from a signal source by the left half beams and the right half beams, respectively, resultant left and right half beams with a main response axis in the source azimuth direction are obtained.

Abstract: A cable termination for connecting cable armor strands to a cable housing end. Individual wire strands are inserted through apertures in an inner hub and are engaged with the inner hub. An outer hub is connected to the inner hub and the housing for selectively tensioning the wire strands. The outer hub can have apertures for engagement with a second set of wire strands, and can be moved relative to the inner hub to selectively balance the tension in the first and second sets of wire strands. The wire strand ends are connected to the hubs at a selected radial distance from the cable center to strengthen the connection, and different structural combinations between the wire strands and the inner and outer hubs can be constructed.

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: The interferometer, which is preferably in the form of a sonar, can have a single projector array and a single receiver array. The projector array comprises a first subset of projector elements that function as a first pseudo projector and a second subset of projector elements that function as a second pseudo projector. One or more of the projector elements belong in both the first and the second subsets, such that one or more of the projector elements function as part of both the first and the second pseudo projectors. A receiver is operative for receiving reflected portions of the signals emitted by the pseudo projectors. A processing system analyzes the signals received by the receiver to at least partially determine the position of an object.

Abstract: For electromagnetic wave distance measurement by the pulse transit time method, short electromagnetic transmission pulses are emitted at periodic transmission instants. The signals received in selected transmission cycles after the respective transmission instants are sampled for obtaining in each of these transmission cycles a sample at a sampling instant in a respective sampling time interval, each sampling instant having a delay dictated by a sampling function relative to the respective transmission instant. The sampling instants exhibit differing delays relative to the respective transmission instant so that the samples in sequence produce an image of the sampled received signal extended in time. The sampling function dictating the delays is generated by a computing circuit, preferably a microcomputer, thus making it possible to make use of any sampling function and to modify sampling of the received signals in any way.

Abstract: A sonar sensor array having a multi-layer tiling arrangement for the indiual elements that increases surface area available for each element while maintaining the inter-element spacing required to avoid spatial aliasing when the received signals are combined to form a sonar beam. The array comprises outer and inner arrays of transducer elements for converting an acoustic signal to an electrical response. The transducer elements of the outer array are positioned such than a grid of isolation spaces separates each of the transducer elements. The transducer elements of the inner array are also positioned such that a grid of isolation spaces separates each one of the transducer elements. The electrical response generated by the transducer elements of the inner and outer arrays are coupled to a beamformer which processes the responses to produce an output signal.

Abstract: Briefly, according to the invention, a noise-cancelling microphone apparatus (400) is disclosed. The microphone (400) comprises a sound transducer (106) for converting sound waves to electrical signals and means for substantially preventing ambient noise from being converted to electrical signal. A circuit (100) is provided for determining the level of noise not prevented form being converted to electrical signal. The microphone (400) further includes a display (148) for indicating when the level of the ambient noise being converted to electrical signal is above a predetermined level.

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 combination of integrated circuit (IC) flatpacs used in combination to tch selected sonar microphone inputs from a circular receiving array to position a beam containing a sounding target intermediate to an equal number of left and right microphone pickups and selectively switching through weighted delay circuits for beam forming to present the target in this receiving beam electronically on a flat display with digital control of "coarse" seven and one-half degrees and "fine" one-tenth degree increments to provide a display of the bearing of the target.

Abstract: Waveform inputs are sampled to provide vector inputs which are coupled to respective ones of a plurality of series connected time delay stages in a processing circuit. Each vector is weighted, or amplified, and time delayed by each stage between its input point and the circuit output. Each stage has switched capacitors and an operational amplifier. The delay of each stage is the period of the capacitor switching frequency. All of the components in the stages and vector input circuitry are solid state switches, capacitors or operational amplifiers and therefore are especially suitable for integration in a monolithic or film substrate. The circuit is particularly adapted to beam steering a plurality of waveform inputs from an array of hydrophones.

Abstract: Quantized delay values used in a digital beamformer are selected so as to minimize the derivative of the beamformer pattern. A first set of quantization error values, one for each hydrophone, is determined from the precise delay values and a second set determined by adding a shading factor times the sample period to each member of the first set. Each set of combinations of members of the first and second sets of error values is then examined to determine which set minimizes the derivative of the beamformer pattern. The quantized delay values are then determined by selecting the quantized delay value corresponding to the error value in the set which minimizes the derivative.

Abstract: With the measurement of spatial movement of test points by means of ultrasonic signals, the problem exists that often interferences occur which may lead to distortion of test results. It is proposed to check the space between sound transmitter and sound receiver by means of electromagnetic waves, in particular light waves, for absence of obstacles, and/or not to use for the derivation of the distances those ultrasonic signals whose transit time and/or amplitude lie outside a given expectancy range, but to discard them.

Abstract: A hydrophone (16) having a short-baseline array of transducers (12A, 12B, and 12C) as well as a long-baseline array of transducers (14A, 14B, and 14C) includes switches 30A, 30B, and 30C) for selectively connecting the outputs of the arrays to a cable (18) that carries the signals to processing circuitry (20) aboard an ocean-going vessel (24). The switches (30A, 30B and 30C) change state in accordance with the output of a narrow-band filter (42), which indicates whether the received signal is of a predetermined frequency and thus is likely to have been produced by an intended source. Due to the delay inherent in the narrow-band filter 42, the processing circuitry (20) thus processes the response of the long-baseline array to the first part of a beacon pulse and the response of the short-baseline array to the second part of the beacon pulse.

Abstract: In an ultrasonic imaging apparatus, when a sampling time space determined corresponding to the respective phases of receiving signals from transducer elements adjacent to each other is shorter than the settling time of sample and hold circuits, these receiving signals are sampled at the same time. Noise is prevented from being mixed with the sample and hold values of these signals.

Abstract: A distance-determining detector and method. A piezoelectric ultrasonic transceiver sends out pulses and receives their reflection and produces an analog output and a trigger output. The analog output is given effect only when it exceeds a threshold level, as shown by a comparator. The trigger output is used for disabling detection during transmission of the transmitter pulse and for producing a time interval during which the analog output is valid, when enabled. An AND gate is connected to the comparator and to the enabled trigger output. Clock pulses are counted, and a flip-flop circuit is connected to the counter and to the output from the AND gate. A multiplying digital-to-analog converter is connected to the flip-flop circuit for determining the distance. There may also be temperature compensation and scaling for the converter for validating the output thereof over a wide range of temperatures.

Abstract: A beamforming method and apparatus utilizing a plurality of sensing elements which are free to take up random positions. Each sensing element generates output signals in response to sensed radiation. The signals are fed to a data process or which generates Fourier frequency components of each output signal and selects a Fourier frequency component for each given radiation frequency to form a group of frequency components. The data processor performs a spatial convolution, interpolation and spatial Fourier transform followed by an averaging procedure in order to obtain an output signal which is indicative of the far field radiation power as a function of angle thus providing the desired beamforming information.

Abstract: An apparatus for locating, classifying and identifying underwater marine animals by means of the sounds they make includes an elongated submersible array adapted to be towed in various directions. The array is made up of subarrays of multiple hydrophones which are arranged along the length of each subarray in groups. By changing the combinations of groups, the frequency response and the directional sensitivity of the array can be varied. The outputs of the groups can be selectively analyzed both visually and audibly for characteristic fish sounds. The received sounds are classified and used for the identification of newly found fish.

Abstract: A device for forming an image of an object by means of ultrasound beams, comprising an array (1) of electroacoustic transducers, means for connecting a selected group of transducers to a delay unit (17) which is arranged to delay the electric signal generated by each transducer of the group by a predetermined period of time and to sum the delayed signals in order to form a resultant signal which is an electrical representation of the acoustic signals originating from a selected distance or from a selected direction. The delay unit (17) is formed by a tapped delay line (19), whose taps (21) serve as inputs for the signals originating from the various transducers and whose output (23) is connected to a signal processing device (25) for the further processing of the resultant signal. Signals are applied to the taps through current sources. The applied signals may be selectively attenuated to effect apodization of the ultrasound beam.

Abstract: A circuit arrangement for forming a succession of group signals in the ranging art from received signals originating from an array of adjacent signal receiving transducers, each successive group signal being associated with a respective group characteristic and being based on the signals received by a respective group of adjacent transducers forming part of the array. The succession of group signals is processed to form a representation of the mean, or average, value of a predetermined number of successive group signals, and a representation of the ratio of the value of one of the group signals of that predetermined number of signals to the mean value is produced.

Abstract: A sonar receiver comprises an inwardly curved reflector arranged to direct received sonar signals onto a transducer system. The transducer system comprises an array of transducers distributed over an inwardly curved path facing the reflector. Each transducer is responsive to sonar signals received from a particular direction to provide an output signal indicative of a reflecting object, the amplitude of which signal is related to distance of the reflecting object.

Abstract: The present invention is directed to a detection system which forms reception beams successively in a series of angular directions. The detection system comprises receiving means for receiving incoming signals in such a manner that the frequency of the incoming signals is varied in accordance with the Doppler effect, and a matched filter for pulse-compressing output signals from said receiving means, with output signals from said matched filter being displayed in an indicator.

Abstract: This invention is a hydrophone (element) sited beamformer which is coupled to an array cable of a horizontal line array. A hydrophone-sited beamformer is coupled to each hydrophone in the array. The element-sited beamformer directly forms beams from the data detected by the hydrophones by delaying and selecting some of the hydrophone detected data and summing this data with the proper shading value.

Abstract: The thinned arrayed transducer for a sonar system includes an array of sonar elements mounted in rows (layers) and columns (staves) on a structure, preferably cylindrical, to form a checkerboard pattern wherein the spacing between adjacent elements in the rows and the columns is equal to or greater than .lambda..sub.m /2, where .lambda..sub.m is the wavelength of the signal of frequency f.sub.o transmitted in the medium where the sonar is being used. The transducer structure is made from a layered cloth impregnated with a phenol based material, and includes openings in which the sonar elements are mounted. The sonar elements which are effectively a half wavelength in length consist of a cylindrical ceramic section fixed end-to-end to a cylindrical metal section. The metal section is made of a loading metal, such as brass. The transmit-receive circuitry energizes the elements by row using a modulated signal to form a variable sonar beam.

Abstract: A high resolution scanning beamformer for a soundhead having a circular or a cylindrical array of hydrophones uses charge coupled devices as transversal filters in a plurality of first stage quadrature sampled phase shift steered beamforming modules. In a second stage, serial-in/serial-out charge coupled devices are used to correct for fill time. The sonar focuses at all nearfield ranges of interest by controllably varying a clocking rate.

Abstract: An ultrasonic transducer arrangement having ultrasonic oscillators, with which electronic delay chains are associated, includes a matrix of column-like ultrasonic oscillators the end faces of which are each connected to control electrodes arranged in the planes of the flat sides of the matrix. On one flat side of the matrix, rows of the oscillators are each provided with a common control line and, on the opposite flat side of the matrix, the jointly controlled groups of ultrasonic oscillators each form a concentric arrangement. This test head can be used selectably as a focusing or as an angle test head and in addition, the focal point can also be displaced in depth.

Abstract: In an exemplary embodiment, the transducer elements are arranged in rows and columns, the transducer elements bein contacted at both sides by oppositely disposed contact surfaces, and switches being associated with the contacts of the one contact surface as well as with the contacts of the other contact surface for the purpose of adjustment of preselectable transmitting and/or receiving surface of transducer elements during a transmitting/receiving cycle, in particular, for the purpose of dynamic focusing. It is an object of the disclosure to construct an ultrasonic array which can function with an optimally low outlay of switches and which if desired also permits a transition to continuously varied apertures.

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: An improvement for a sonar is provided wherein the improvement includes a ne array of N listening transducer elements, each listening element being capable of receiving an acoustic signal and outputting a corresponding electrical signal. A plurality of beamformers is provided wherein each beamformer has an input and an output, the input of each beamformer receiving the output from each listening element. A switching device is interconnected between the listening elements and the beamformers for alternately switching the outputs of the listening elements to each beamformer between two modes, one mode being a predetermined order and the other mode being an inversion of the predetermined order. With this arrangement only half the normal number of beamformers is required, thereby significantly reducing the weight and size of the sonar.

Abstract: A parallel digital beam-former for an array of hydrophones. The output of ch hydrophone is fed into a different shift register. Each register stores the sampled time history of the hydrophone. The contents of each register are fed serially into a different gating circuit in the time interval between each new input signal sample and the output of each gating circuit is fed in parallel with the output of each of the other gating circuits to a group of beam gates. The output of each beam gate is then fed to a different binary counter which sums the signals. Each binary counter is associated with a different beam.

Abstract: There is described a digital sonar receiver having a novel beamformer, own doppler nullifier (O.D.N.), and adaptive time varied gain controller. The beamformer interrogates a multi-element transducer by utilizing an interleaved sampling scheme which samples the elements in the trandsducer array sequentially, in such a fashion that continuous, uniformly spaced samples are obtained. The samples are subsequently converted into digital format, weighed and summed. The O.D.N. eliminates the own ship's doppler effect on the beam output signal resulting in a half beam output signal representative of the target doppler. The O.D.N. offsets the frequency of the beam output signal and a digital generated signal representative of the own ship's doppler. The O.D.N. multiplies these two offsetted signals resulting in a signal lying in each of the sum and difference frequency bands for which the signal lying in the difference frequency band corresponds to the target doppler.

Abstract: An ultrasonic detection system having an array of ultrasonic transducers that are uniformly closely disposed relative to each other such that the active surfaces for transmission or reception are maintained on a straight or curved line. The transducers form radiation or reception beams in a specific direction. Beam orientation is accomplished by selecting a group of transducers from the array and/or respectively applying appropriate phase-shifts to the signals to be fed to each of the transducers or to the signals produced from each of the transducers. Shields are maintained between two adjacent transducers for suppression of sidelobes.

Abstract: A serial phase shift beamformer characterized by a charge transfer device for progressive clocked transfer of quadrature component analog samples of the scanned outputs of a multiplicity of transducer elements in a curved array. Weighting resistors effect scaling of the analog samples during parallel readout of X and Y component samples prior to summation of like components and derivation of the square root of the sum of the squares of the X and Y summations to provide formed beam amplitude signals.

Abstract: 1.

Abstract: 1.

Abstract: This disclosure relates to multi-angular sector sound transmitting and receiving systems embodying stacked pluralities of arrays of transducers and novel scanning arrangements and circuits for enabling the display of the sound-wave reflections emanating from multiple angular sectors upon a novel preferably spirally deflected cathode-ray-tube display system.

Abstract: A linear transducer array with low overall side lobe sensitivity for use in steered beam imagers has a different interelement spacing for transmit than for receive, and preferably has a shorter transmit array with elements spaced at one-half wavelength as the center portion of a longer receive array whose unit elements are spaced at a full wavelength. Two or more elements in the center portion can be coupled together to a receiving channel to maintain constant spacing for the receive aperture in a 100% active transducer.

Abstract: A digital beamformer for use with a cylindrical sonar array effects sequeal quadrature pair sampling of the outputs of M array elements used to form each beam, the resulting X and Y samples being digitized and fed alternatively to two serial-in, parallel out shift registers having M stages. M shading modules are responsive to the digitized element output samples in the corresponding stages of the two shift registers to alternately provide M shaded X and Y outputs. A multiple layer digital adder tree sums pairs of adjacent shaded X outputs and adjacent shaded Y outputs to provide the final beamformer output.