Abstract: Technologies directed to energy efficient phase shifting in digital beamforming in phased array antennas in communication systems are described. Digital signal processing (DSP) circuitry includes a first phase shifter that generates second data by phase shifting first data according to a rotation-based operation without multiplication of the second data, a second phase shifter that generates fourth data by phase shifting third data according to the rotation-based operation without multiplication of the fourth data, a combiner that generates fifth data by adding the second data and the fourth data, and a multiplier that generates sixth data by multiplying the fifth data by a constant value.

Abstract: A method for providing a broadband constant beam width acoustic array includes providing a transducer array in an axisymmetric configuration. A beam width is specified, and an integer order Legendre polynomial is determined for that beam width. A control parameter is determined that will increase the integer order Legendre polynomial to that beam width. The Legendre polynomial is used to provide a shading function for the array of transducers that will give the specified beam width.

Abstract: A system and method for extending the path length of an electromagnetic wave signal traveling between apertures is disclosed.

Abstract: Methods, systems, and computer-readable media are provided for processing seismic data. The method includes receiving a seismic data set associated with a domain, and calculating a seismic attribute associated with the domain from the seismic data set. The method also includes performing one or more mathematical morphology operations on the seismic attribute to generate a processed attribute associated with the domain.

Abstract: A method using an may microphone to cancel echo applies to a sound receiving system and comprises steps: an array microphone receiving a sound source and outputting a plurality of analog acoustic signals formed from the sound source; an A/D converter converting the analog acoustic signals into a plurality of digital acoustic signals; a digital signal processor respectively using an adaptive beamforming process and a blocking matrix filtering process to convert the digital acoustic signals into a primary acoustic signal and at least one noise signal; and the digital signal processor using a multiple-input cancelling process to subtract the noise signal from the primary acoustic signal to obtain an acoustic signal where the echo has been cancelled. Thereby, the present invention can eliminate the systematic errors of the array microphone of the sound receiving system and improves the robustness of the acoustic signal.

Abstract: A storage unit (106) stores pieces of information regarding intensities of ultrasound waves detected by multiple oscillators (101) in time series. The multiple oscillators (101) receives an ultrasound wave reflected on an object (107), to which a second ultrasound wave (108) generated by an ultrasound probe (102) is focused, in order from an oscillator closest to the object (107). The second ultrasound wave (108) is transmitted in a direction different from that of a first ultrasound wave (103). Information regarding an intensity of the ultrasound wave reflected on the object (107), which is obtained by storing in the storage unit (106) in order from the oscillator closest to the object (107), is obtained. This information is subtracted from the pieces of information stored in the storage unit (106). Thus, a received signal from a side lobe is extracted to be subtracted from a whole received signal.

Abstract: Described herein is sonar localization apparatus which comprises a plurality of acoustic transducers (6) arranged to define at least two end fire arrays (2, 4) each of which produces a sonar beam (10, 12) suitable for the detection of objects in the near field.

Abstract: The invention relates to a synthetic sonar antenna and more particularly to the self-calibration of such an antenna. It consists in minimizing the number of sensors of the reception antenna by fixing the reduced pitch between the sensors, imposed by the precision of the self-calibration, solely at the two ends of the antenna. According to a variant, the reduced pitch is fixed at just one end of the antenna. It makes it possible to increase the precision of the self-calibration with a smaller number of sensors than in the prior art.

Abstract: A sidelobe canceller for a transducer arrangement such as an antenna or sonar transducer uses a main transducer and one or more auxiliary transducers. The auxiliary received signals are weighted by FIR filters or by multipliers, and the weighted auxiliary signals are summed, and the summed, weighted auxiliary signals are subtracted from the main signal to produce the desired low-sidelobe main signal. The weighting signals are generated in conventional manner from intermediate weighted signals. The intermediate weighting signals are produced by a reduced-hardware arrangement. When FIR filters are used, the signals being multiplied by weights include mutually delayed samples.

Abstract: Permeability is one of the most important factors in influencing the commercial viability of a hydrocarbon reservoir. So far, permeability cannot be measured directly in-situ in reservoir formations. This invention relates to the field of estimating in-situ permeability of the reservoir rock formations. The measurements can be made across two wells or in a single well. Due to the morphology of their pore interconnections and the pore fluids in the rock, permeable rocks are elastically nonlinear. In a permeable rock, which is elastically nonlinear, the interactions between two elastic waves can be used in a unique way to map its physical properties. In this invention, the interaction of an elastic wave generated within the permeable rock with an externally generated seismic signal is used to determine the bulk tortuosity and bulk permeability of a reservoir rock formation.

Abstract: A multi-arm elliptic logarithmic spiral array that is particularly effective in off-axis beamforming applications. The array is formed by providing an elliptic logarithmic spiral and a plurality of concentric ellipses which intersect with angularly spaced apart sample points on the elliptic logarithmic spiral. An odd number of sample points are included on each ellipse. The array of the present invention is particularly effective in off-axis beamforming applications, such as aeroacoustic test applications within wind tunnels, where the location of the array is fixed and the source of noise is positioned off axis of the array.

Abstract: A narrowband beamformer for extracting a mainbeam having a frequency, &OHgr;, that is received at a beamsteered sensor array includes a plurality of nonlinear oscillators. Each nonlinear oscillator operates on a signal from one of the beamsteered sensors to produce a nonlinear oscillator output. A summer receives and sums all of the nonlinear oscillator outputs. Each nonlinear oscillator is coupled to at least one other nonlinear oscillator to create a signal in the summer output having a frequency of approximately, &OHgr;, in response to receipt of the mainbeam signal by the sensor array. Further, the nonlinear oscillators are coupled to create a spectrum of signals in the summer output that are centered around a frequency, {overscore (&ohgr;)}, in response to receipt of a directional interference signal by the sensor array. A matched filter is used to isolate the frequency, &OHgr;, to thus extract the mainbeam from the directional interference.

Abstract: A class of planar arrays having broad frequency range applications for source location, source imaging or target illumination with projected beams is described in this disclosure. The non-redundant arrays are circularly symmetric and made up of a plurality of sensing and/or transmitting elements arranged so as to substantially eliminate grating lobes for a broad range of frequencies. Signals received from or transmitted to the elements are appropriately phased to control the beam of the array.

Abstract: New apodization functions providing an effective rejection of side lobe amplitude level within wide range of beam steering angles are described in this invention. A central amplitude apodization function (13) reduces amplitudes for the central section of transmit and receive array individual elements. A time apodization function (14) changes a duration of transmit pulses. A duration of transmit pulses is short for central section of transmit array and increases for outlying transmit individual elements. A frequency apodization function (15) changes frequency of transmit pulses for different transmit individual elements. The use of new apodization function allows realization of portable acoustic scanners. Some versions of a portable acoustic scanner design and a version with time compression of echo signals are described.

Abstract: An adaptive beamforming system for broadband sonar with a convergence time on the order of the pulse duration and effective interference nulling capabilities which enhance desirable echoes. The method uses an element based time implementation algorithm in which beam data that is formed in the direction of each interferer is successively subtracted from the element data using an adaptive FIR filter. The system can be applied to impulsive source sonar data and passive sonar data.

Abstract: A method of amplitude shading in the time domain is used to control side es in the frequency domain. Each of a plurality of limited dynamic range amplifiers is capable of generating a corresponding output with a frequency response when input power is applied thereto. The amplitude of the input power supplied to each amplifier is controlled in accordance with an amplitude shading function in order to modify each of the corresponding amplifier outputs. Each amplifier output is modified such that the width of each main lobe is realized while the side lobes are reduced. The amplitude shading function used by the present method is a one-half cycle cos.sup.2 function with a DC offset.

Abstract: A method and apparatus for enhancing resolution of range estimates in all echo location systems and, specifically, such systems as Radar, Sonar, and Synthetic Aperture Radar (SAR), for example. The invention utilizes high order signal processing to "sharpen" or contract the main lobe of the processing system ambiguity function and suppress its side lobes, for a given transmission pulse bandwidth. The method and apparatus may be implemented in the frequency domain or time domain. Enhanced resolution is achieved by using a filter (MSC filter), according to this invention, in the echo location data processing system so that the received echo data is processed by the MSC filter to produce a signal that exhibits enhanced range resolution. The MSC filter output, H(.omega.), which is specific to the transmitted pulse waveform, is the ratio of a high-order manipulation of the transmitted signal with its modified spectral profile.

Abstract: The present invention is a system and technique for reducing the effective beam width of a receive beam for a sensing system, for example a sonar or radar system. The sensing system includes a plurality of physical sensors each for measuring a receive signal wherein each receive signal includes a first and second data processing unit. The sensing system may include means for computing sensor data for at least one extrapolated-sensor, including, first extrapolation means for computing a first extrapolated-sensor data unit of the at least one extrapolated-sensor by extrapolation of a first data processing unit of the plurality of physical sensors, and second extrapolation means for computing a second extrapolated-sensor data unit of the at least one extrapolated-sensor by extrapolation of a second data processing unit of the plurality of physical sensors.

Abstract: In an adaptive array beamformer, a spatial beamforming filter is connected to a sensor array for respectively filtering and summing array signals to produce a first filter output containing a target signal that arrives in a specified direction. First adaptive filters provide transversal-filtering the first filter output to produce a second filter output not containing the target signal, using a first error signal by restraining their tap weight coefficients. The array signals are further coupled to subtractors. Each subtractor detects a difference between the second filter output of the corresponding first adaptive filter and the corresponding sensor signal to derive the first error signal. Second adaptive filters provide transversal-filtering the first error signals of the subtractors to produce third filter outputs, using a second error signal, by restraining their tap weight coefficients.

Abstract: A multibeam side-look sonar system includes a projecting transducer that projects a beam of acoustic energy to insonify a target area and a receiving transducer having a plurality of transducer elements arranged in a linear array. Each of the transducer elements generates a beam signal in response to acoustic energy reflected from the target area. A beamforming circuit, coupled to the receiving transducer, processes the beam signals generated by the transducer elements to form a beam pattern. The beam pattern for an end beam on the receiving transducer has a main lobe and grating side lobes. One of the grating side lobes may be insonified by the projected beam of acoustic energy. A shading circuit, coupled between the receiving transducer and the beamforming circuit, amplifies the beam signals with respective gains, and adjusts each of the respective gains to reduce an amplitude level of the grating side lobe insonified by the projected beam of acoustic energy.

Abstract: A module formed by an array of pipes is provided for installation in front of existing radar and sonar transducers. A preferred array is formed by a section of honeycomb material in which each pipe has a hexagonal cross section and is mounted in an insulating sheath. Each pipe acts as a radiator of energy from a transducer that combine in phase to produce a beam narrower than the beam from the transducer. The module is effective to improve the range and resolution of forward-looking radar and sonar devices.

Abstract: The present invention is a system and technique for reducing the effective beam width of a receive beam for a sensing system, for example a sonar or radar system. The sensing system includes a plurality of physical sensors each for measuring a receive signal wherein each receive signal includes a first and second data processing unit. The sensing system may include means for computing sensor data for at least one extrapolated-sensor, including, first extrapolation means for computing a first extrapolated-sensor data unit of the at least one extrapolated-sensor by extrapolation of a first data processing unit of the plurality of physical sensors, and second extrapolation means for computing a second extrapolated-sensor data unit of the at least one extrapolated-sensor by extrapolation of a second data processing unit of the plurality of physical sensors.

Abstract: A method and apparatus for identifying a remote target includes a transmitter for transmitting pulses of energy toward the target for generating echo signals, and a receiver for receiving the echo signals, and for generating received signals representing the target, noise and clutter. The received signals are applied through a plurality of cascaded channels, each including a Doppler filter cascaded with a multiplier, each also including range sidelobe suppression, for, in each of the cascaded channels, narrowband filtering the signals passing therethrough about a controllable center frequency, and for, if necessary, converting the signals passing therethrough to baseband, for thereby applying one of a plurality of Doppler filtered baseband signals to the input of each of the range sidelobe suppressors of each of the cascaded channels. The power of the Doppler filtered baseband signals in each range bin is evaluated for determining the frequency at which the spectral density is greatest.

Abstract: An ultrasonic detecting apparatus which includes a sequence generating means and a transmission signal generating means for generating a transmission signal corresponding to the sequence. The detecting apparatus also includes a transmitting means to transmit waves, which may be ultrasonic waves, to an object and a receiving means for receiving an echo corresponding to the transmission signal. A correlation operation means performs a correlation operation with respect to the echo. In another general aspect, the sequence generating means may generate more than one sequence, some of whose auto-correlation functions produce substantially zero sidelobe in the summed result. In a further general aspect, the sequence generating means generates two or more sequences, with each of the sequences being different from the others and having substantially the same auto-correlation function as the others.

Abstract: An ultrasonic detecting apparatus which includes a generator which generates more than three transmission signals. The detecting apparatus also includes a transmitter/receiver which transmits waves, which may be ultrasonic waves, to an object and receives echoes corresponding to the transmission signal. A correlator performs correlation operations with respect to the echoes. The results of the correlation operations are processed to obtain a signal with substantially zero side lobes.

Abstract: A pulsed transmission, single frequency, high resolution sonar system has duced grating (side) lobes achieved by employing mechanically fixed antenna array stave tilt angles together with electronic focussing in which phase shifts are substituted for time delays.

Abstract: A method for producing simple seismic wavelet shapes with minimal side lobe energy for use as reference signals for seismic vibrators is disclosed.

Abstract: A signal processor eliminates sidelobe response from signals produced by a spaced antenna array that forms a single beam using spatial frequencies. The signal processor also produces error signals. The signal processor uses a phase coherent local oscillator to simultaneously convert the wavefront signal from each element of the antenna array to three different first intermediate frequency signals IF. The first IF signals of each element are cross-correlated with the first IF signals from each of the other array elements to form the signals containing sampled spatial frequency components IF.sub.2. Cross-correlating a second time using the sampled spatial frequencies as inputs produces signals containing derived spatial frequency components IF.sub.3. The signals containing derived spatial frequency components are synchronously detected (phase compared) and summed to provide a single beam output signal.

Abstract: A pulsed-transmission, narrow-band sonar system has a first antenna array ich is unshaded and a second array partitioned into four parts, the center two of which are electrically connected in parallel and the outer two of which are connected in series.

Abstract: A side-looking sonar transducer which has sound absorbing material extending forwardly of the active surface of the transducer elements to diminish the acoustic response over a predetermined zone for reducing the effect of erroneous reflection signals. The surface of the sound absorbing material has a series of sharp peaks and valleys.

Abstract: An array for receiving wave energy at a pair of widely spaced frequencies has receiving elements arranged to function as a half-wave array for the lower frequency and as a random array for the higher frequency. A plurality of receiving elements are arranged in an array with the receiving elements having nominal positions spaced apart such that spacing between adjacent nominal positions is approximately one half the wavelength .lambda. of the wave having the lower frequency. The receiving elements are randomly distributed about their respective nominal positions with each receiving element being within a distance of .epsilon..lambda..sub.o of its corresponding nominal position where .epsilon. is a randomization parameter and .lambda..sub.o is the wavelength of the higher frequency wave.

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 square law detection circuit for energy signals such as sonar signals wherein the signal processing eliminates the side lobe detection of false targets by eliminating the side lobes themselves without significant energy degradation of the main lobe of the beam pattern associated with the sonar equipment.

Abstract: Antenna, in particular for a sonar, allowing to form directional channels by feeding the transducers by a reduced number of sources by means of an interpolation network that permits to maintain to a low level the image lobes in spite of this reduction of the number of sources.

Abstract: A method of reducing horizontally propagating pressure waves in marine seismic exploration improves the signal-to-noise ratio at associated receivers and reduces interference at unassociated receivers. Marine vibrators are arranged into an array with a given separation between each vibrator, so that horizontally propagating pressure waves from the vibrators which generally traverse the array are out-of-phase at most frequencies of vibration. The amplitude output from each vibrator varies with the output frequency of each vibrator to maximize the cancellation of out-of-phase pressure waves along the array. A receiver, which usually includes a plurality of hydrophones disposed in a streamer, is spaced from the marine vibrators at a distance sufficient to establish the receiver as being in the far-field. The output of each of the marine vibrators is locked in phase and frequency with a known pilot signal so that downwardly propagating pressure waves are substantially unaffected.

Abstract: An ultrasonic measuring transducer system in which an ultrasonic transducer transmits an ultrasonic pressure wave and receives a return echo from a target and an electronic circuitry means converts the received pulses to arrange information to a target. The ultrasonic transducer is mounted in a wall of a plenum chamber. Air flow passages or apertures surround the ultrasonic transducer and air from a supply under pressure is connected to said plenum chamber. A temperature (or velocity of sound) measuring device is mounted in the plenum chamber for measuring the temperature from which the speed of sound in the medium is determined, and a measuring chamber forming tube surrounding the transducer and air outlet apertures provide a space in which air flow is maintained at a relatively constant rate and the temperature in substantially all of the measuring path and space between the target and said ultrasonic transducer is essentially the same as in the plenum chamber.

Abstract: A housing adapted for receiving a sonic transducer capable of projecting and receiving a sonic pattern having a primary lobe and a secondary lobe. The housing has an end wall for receiving the sonic transducer and a restrictive wall for intercepting the secondary lobe of the sonic pattern in one quadrant and reflecting that portion of the secondary lobe into the opposite quadrant. A pair of side walls substantially intercept and reflect the secondary lobe in quadrants adjacent the one quardant to provide more uniform sonic pattern. The side walls may be disposed at an angle outward from the direction of projection of the primary lobe having a value of from 0.2 to 0.3 of the value of the angle the secondary lobe makes with the primary lobe.

Abstract: Disclosed herein is an omnidirectional distance measurement system which transmits and receives ultrasound waves using as many as four transmitting-receiving transducers having specially shaped beamwidths. Through the use of four such ultrasonic transducers, the system may be set up to obtain any beamwidth from 5.degree. up to 360.degree. in both the horizontal and vertical planes. In the preferred embodiment, the present invention is able to detect the distance and direction to up to four objects in a prescribed work area at any one time and may also detect the speed of any one of the objects if desired.

Abstract: An apodization attenuation circuit to achieve a selected percent Gaussian apodization of a focused ultrasound wavefront when transmitted from a linear or phased array. The circuit uses a string of resistors, one resistor positioned between the drivers of each element in the transducer array. Each node of the resistor string functions as the reference potential input for one driver. Each node includes a pair of normally open switches, one of which may be closed to common and one of which may be closed to full reference potential. By closing four switches, two to common and two to full reference potential, a profile of potential of a selected percent Gaussian apodization can be achieved such that the output pulse magnitude of each transducer element in an aperture varies as a Gaussian function of its distance from the center of the aperture.

Abstract: A system of emission array with several pairs of emitting transducers to emit simultaneously and covering contiguous frequency sub-bands of a band B. The sub-bands have a width which is less than or at most equal to the width inducing an acceptable displacement of the directivity lobes of the emission pattern of a pair of arrays. The emitters of a single pair are spaced by a distance of L.sub.i and emit signal pulses at frequency f.sub.i and of duration .tau..sub.e 1/.DELTA.f, the products L.sub.i f.sub.i being equal for all the pairs of emitters.The emission patterns of the various pairs of emitters accordingly coincide precisely, and, as the emitters are supplied with signals emerging from the oscillators which are in phase at the center of the pulse of duration .tau..sub.e, the pulse resulting from the superposition of the emitted signals is compressed in time.

Abstract: The present invention relates to a beam forming device for forming a uniform radiation beam and/or a reception beam. In radiation, the transducer is vibrated in such a way that the pressure of a sound wave produced from each point of the vibrating surface of the transducer is determined based on a weight function, thereby forming a radiation beam. In reception, electric signals are derived based on the sound energy received in a manner that the amplitude level of an electric signal produced based on the sound energy received by each point of the vibrating surface of the transducer is determined based on a weight function, and the derived signals are combined with one another to form a reception beam.

Abstract: An ultrasonic horn assembly includes a horn with a bore tapering from a throat out to a mouth. An ultrasonic transducer is mounted in the throat of the horn. A beam narrowing insert includes a headpiece which tapers smoothly from a larger diameter base to a smaller diameter top. A stem projects from the base so that the base and stem define an annular shoulder which faces the transducer. A blind bore in the stem terminates at a flat bottom surface which faces the transducer. A ring receives the transducer and webs project inwardly therefrom to support the headpiece in spaced relationship to the transducer.

Abstract: A cylindrical transducer for use as a low frequency hydrophone and having inner and outer electrodes at least one of which is deposited in a certain predetermined pattern having smooth continuous lines whereby the electrode coverage varies as a function of transducer axial length.

Abstract: In ultrasonic transmission from and reception by an array probe in a phased array sonar, when an ultrasonic beam is directed substantially in front of the array probe, an ultrasonic wave having a high center frequency f.sub.o, or a bandwidth extending into higher frequencies, is transmitted and/or received in order to insure a high image resolution. When the ultrasonic beam is steered sideways, an ultrasonic wave having a lower center frequency f.sub.o, or a higher frequency range cutoff in relation to a steering angle .theta., is transmitted and/or received in order to increase the angle at which grating lobes are generated and hence prevent such grating lobes from entering the angle range of the field of view.

Abstract: Electronically changing the effective element spacing of an array of acoustic transducer elements between the transmit and receive modes of operation of an ultrasound apparatus results in reducing the deleterious effects of grating lobes present in the pattern of the array because of element spacings in excess of one half of a wavelength. A linear or quadratic time delay distribution, or both simultaneously, is applied to the array for scanning and/or focusing by setting individually the time delay of the energy associated with each element of the array during one mode of operation, e.g. transmit. The array is organized into groups of elements, e.g. pairs, and the time delay distribution is applied by setting the time delay of the energy associated with each group of the array during the remaining mode of operation, e.g. receive.

Abstract: A sonar beam steering arrangement in which a circular array of electroacoustic transducers are sampled in sequence, the samples being digitized and stored serially in a shift register. The register is several cycles long so that samples from all of the `illuminated` transducers can be stored simultaneously. The various stages have resistance tappings of different values such that a linear broadside array is simulated for a particular transducer at a particular stage in the shift register cycle. As the samples progress through the register each transducer in turn acquires this simulated broadside array and thus provides a narrow beam 360.degree. scan. Interpolation between adjacent transducer `dead-ahead` direction is obtained by (e.g.) triplicating the shift register and adjusting the weightings slightly from each register to the next.

Abstract: A decoder circuit is provided which employs digital sampling and correlation apparatus to detect the presence of a received tone signal exhibiting a predetermined frequency. Samples of received tone signals are taken and, in effect, multiplied by a substantially rectangular observation window which includes a bite interval of selected duration and location therein. A correlator correlates the windowed samples to detect samples corresponding to the predetermined frequency (main lobe frequency). A significant decrease in undesired side lobe response is thus achieved.

Abstract: An array with high resolving power and low secondary lobe levels, comprising a receiving array formed of transducers along its length L.sub.R, two of these transducers, separated by a distance L.sub.E, also forming the transmitters. The change from transmission to reception and back is effectuated by switches. Signals received by transducers are weighted by resistors before being delivered to beam forming circuits, containing multi-terminal phase shifters and a wiring matrix and adders. The weighting function and ratio L.sub.E /L.sub.R are chosen to ensure that the overall transmission-reception system diagram has high resolving power and low secondary lobe levels.

Abstract: A frequency independent acoustic antenna has an acoustic filter plate located between a lens and sensor/transmitter. When used as a receiver this arrangement of components enables the lens to receive plane waves emanating from a source. This results in materially enhanced beam forming characteristics and performance. The arrangement is also suitable for use in the transmitting mode.

Abstract: The radiation pattern of shaded single element piezoelectric transducers and transducer arrays has reduced side lobe levels. Shading to reduce the intensity of emitted ultrasound at the edges of the transducer relative to the center is realized by varying the electric/acoustic conversion efficiency or polarization of the piezoelectric material, by having different mechanical element lengths, by selectively poling the piezoelectric material to produce poled and unpoled regions, and by control of electrode geometry. The shading of a phased array ultrasonic transducer is described in both lateral dimensions.