Abstract: An acoustic tracking system that uses an array of microphones to determine the location of an acoustical source. Several points in space are determined to be potential locations of an acoustical source. Beamforming parameters for the array of microphones are determined at each potential location. The beamforming parameters are applied to the sound received by the microphone array for all of the potential locations and data is gathered for each beam. The most likely location is then determined by comparing the data from each beam. Once the location is determined, a camera is directed toward this source.

Abstract: A system and method for acoustic source location using a horizontal and vertical microphone array. Tilt sensors are provided within each array to allow full determination of the tilt of each array. Based on the acoustic source location results, an image capture device may be maneuvered to focus in the direction of the acoustic source location.

Abstract: An acoustic array platform comprising multiple spaced microphones and associated processing electronics/algorithms projects distinct beams in a chosen look direction across which moving objects such as vehicles pass. These moving objects are accurately detected, classified and counted at extended ranges. The acoustic microphone array employs optimized beamforming to create specially focused listening directions that function as a “motion detector” and “trip line counter”. Algorithms detect and confirm the appropriate presence of objects moving through the beams and perform other algorithmic tests to verify that the object is a valid object to be counted. The proposed approach is realized with modest sized acoustic arrays and a reasonable number of microphones by employing an adaptive beamforming algorithm that achieves enhanced directivity in a principal look direction and which significantly reduces the effects of interferers outside the precise steering direction of the “trip line”.

Abstract: A method for enhanced Capon beamforming includes the steps of providing a sensor array including a plurality of sensor elements where an array steering vector corresponding to a signal of interest (SOI) is unknown. A covariance matrix fitting relation is bounded for the unknown array steering vector by constraining the array steering vector using a constant norm and a spherical uncertainty set. The matrix fitting relation is then solved to provide an estimate of said array steering vector.

Abstract: The invention concerns panoramic audio devices to process the impulsive signals received by passive sonars. It consists in isolating, in each beam, impulsive signals in the frequency and time domains and then filtering them according to the characteristics of the human ear. All left and right signals are then summed in order to be listened to in a headset. It allows rapid processing of impulsive signals.

Abstract: A system and method to provide maximum power over large angular sectors using an array of transducers is disclosed. Array segments of transducers and phase shifters form a beam from each of the array segments, wherein the set of beams overlap to form a large sector coverage beam. The phase of each of the signals fed to the radiating elements is shifted, such that the difference between beam point directions of the beams of two adjacent array segments is substantially equal to one half of the sum of the beamwidths of the beams of the two adjacent array segments. The phase of each of the signals fed to the radiating elements may also be shifted in proportion to the square of the distance between one end of the array of transducers and the position of each of the plurality of radiating elements.

Abstract: A data-based technique is disclosed that defines the amplitude and phase of acoustic signals for detection as they propagate across an array of sensor elements for each array incident angle of interest. The definitions of the acoustic signals are then used to constrain adaptive noise suppression operating routines from canceling desired acoustic representative of desired incident direction detector. The data-based technique of defining acoustic signals also leads to a greater reduction of noise in directions where signal is not present. The use of this technique within an adaptive-array-beamforming-processor, and more particularly in connection with the provision of data-based steering vectors therefor, results in an improvement in the ability to detect acoustic signals imbedded in noise.

Abstract: A receiving beam is formed using 60 elements arranged in a 90° sector area of a cylindrical receiving array. Receiving beam 0 is formed with elements 0-59 divided into two (front and rear) groups. Specifically, the elements 0-59 are divided into rear group 1 (elements 0-8, 51-59) and front group 2 (elements 9-50) in the beam direction, and the receiving beam is formed by using sample data obtained from the transducer elements 0-8, 51-59 of group 1 in a current scanning cycle as well as sample data obtained from the transducer elements 9-50 of group 2 in a preceding scanning cycle. This approach makes it possible to form the receiving beam such that incoming waves of a short-pulse signal would simultaneously hit the relevant transducer elements of the receiving array and thereby improve directivity and sensitivity of the receiving beam for the reception of short-pulse waves.

Abstract: A system and method for processing sonar information from an underwater hydrophone array, at frequencies having wavelengths less than two times a spacing between adjacent hydrophones. The method and system all for processing received underwater waveforms at high frequency limits beyond the mechanical limits of the array.

Abstract: A received beam-forming apparatus is disclosed is which echo signals received by multiple ultrasonic transducer elements arranged in a linear form are sampled at a specific scanning frequency to obtain sample data. A receiving beam-forming apparatus includes a memory which stores the sample data derived from multiple scanning cycles; and a beamformer which divides the multiple ultrasonic transducer elements into multiple blocks, reads out the sample data derived from different scanning cycles for the individual blocks from said memory, and forms a receiving beam in a specific direction using the individual sample data which have been read out. A sonar system using the receiving-beam forming apparatus is also disclosed as is a matched filter which selects an arc-shaped part of an ultrasonic transducer element array.

Abstract: An ultrasonic signal is used to link a beacon unit to a tracker unit to provide a tracking and navigation system for firefighters to use in a smoke filled environment at the scene of a fire. The beacon unit transmits an omnidirectional ultrasonic signal. The tracker unit, using a directional ultrasonic receiver provides a display or other indication of the signal strength of the received ultrasonic signal to allow the direction to the beacon unit to be determined. The ultrasonic signal provided by the beacon unit may be pulse modulated to include digitally encoded data that may be used to identify particular individuals, objects, materials, dangers, or exits. In addition, the tracker unit may be provided with a transmitter and the beacon unit provided with a receiver such that audio communication may be established therebetween.

Abstract: A method and system for processing received sonar signals. The method and system generate bearing data signals based on the received sonar signal. The method and system continuously determine the signal strength of the received sonar signal and also continuously determine the total noise from the received sonar signal in the ocean environment in which the target is located. The method and system provide a sensor gain in response to the determined total noise and the signal strength, and adaptively calculate filter coefficients from the sensor gain and the determined total noise. The method and system also filter the generated bearing data signals using a filter having the calculated filter coefficients.

Abstract: A method for enhanced Capon beamforming, referred to herein as an advanced robust Capon beamformer (advanced RCB), includes the steps of providing a sensor array including a plurality of sensor elements, wherein an array steering vector corresponding to a signal of interest (SOI) is unknown. The array steering vector is represented by an ellipsoidal uncertainty set. A covariance fitting relation for the array steering vector is bounded with the uncertainty ellipsoid. The matrix fitting relation is solved to provide an estimate of the array steering vector.

Abstract: A power transmission system using directional ultrasound for power transmission includes a transmitting device and a receiving device. The transmitting device has a set of ultrasound transducers forming an ultrasound transducer array, wherein the array is a set of spaced individual transducers placed in the X-Y plane disposed to generate an ultrasound beam in the Z direction.

Abstract: The invention concerns panoramic audio devices to process the impulsive signals received by passive sonars.

Abstract: A method for enhanced Capon beamforming, referred to herein as an advanced robust Capon beamformer (advanced RCB), includes the steps of providing a sensor array including a plurality of sensor elements, wherein an array steering vector corresponding to a signal of interest (SOI) is unknown. The array steering vector is represented by an ellipsoidal uncertainty set. A covariance fitting relation for the array steering vector is bounded with the uncertainty ellipsoid. The matrix fitting relation is solved to provide an estimate of the array steering vector.

Abstract: A hearing device comprising at least two microphones, a processor and an output for further processing in a reproducer, the microphones being electrically coupled to the processor, and the output for further processing in a reproducer being connected to the processor. The processor comprises: a summer providing a sum signal of the microphone signals, and to which summer a proportional amplifier is connected, and a summer for providing a difference signal of the microphone signals, to which summer an integrator is connected, and that the proportional amplifier and the integrator are coupled on the output side to a third summer providing a sum signal of the proportional amplifier and the integrator, and that the third summer forms the output for further processing in a reproducer.

Abstract: A digital multiline beamformer is provided which produces multiple receive beams in response to a single transmit event. An embodiment of the present invention includes a bulk delay which provides a common steering delay applicable to all of the beams received at one time. The bulk delay is succeeded by parallel filter processing paths which produce finely focused multiple beams simultaneously. In one embodiment a multiphase filter produces the samples for multiple beams, which is advantageous when the number of simultaneously produced beams is greater than the number of phases produced by the fine focus filter.

Abstract: An apparatus for phase coherent underwater communications includes a transmitter; a receiver, including a processor for jointly performing coherent diversity combining, carrier recovery, channel equalization and synchronization; and an antenna array that includes a plurality of antenna sub-arrays for alternately transmitting a signal generated by the transmitter and for receiving an incoming signal. Each of the antenna sub-arrays includes a plurality of underwater sensors positioned such that each of the sensors is spaced at about one half the wavelength of the receiver/transmitter operating frequency from any adjacent sensor in the same sub-array. At least one of the sub-arrays has a centerpoint vertically spaced apart from a centerpoint of an adjacent sub-array at a distance about equal to or larger than a vertical correlation length of a received signal. The individual sub-arrays are beamformed, e.g. using a plane-wave delay-and-sum (or phase-steering) method.

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: A multistatic passive sonar is disclosed having a time-aligned source combiner, that exploits the cross-correlation between a target beam and all other beams to detect and measure the range of a target. This combiner performs long-term cross-correlation between the target beam and each individual source beam, and then aggregates the individual correlation results, time aligned based on the scenario geometry, and averaged to enhance the composite signal-to-noise ratio of the range measurement. In doing so, innocuous acoustic sources may be opportunistically exploited as if the array were part of a multi-static, active (e.g., sonar) system.

Abstract: An ultrasonic signal is used to link a beacon unit to a tracker unit to provide a tracking and navigation system for firefighters to use in a smoke filled environment at the scene of a fire. The beacon unit transmits an omnidirectional ultrasonic signal. The tracker unit, using a directional ultrasonic receiver provides a display or other indication of the signal strength of the received ultrasonic signal to allow the direction to the beacon unit to be determined. The ultrasonic signal provided by the beacon unit may be pulse modulated to include digitally encoded data that may be used to identify particular individuals, objects, materials, dangers, or exits. In addition, the tracker unit may be provided with a transmitter and the beacon unit provided with a receiver such that audio communication may be established therebetween.

Abstract: A sensor array receiving system which incorporates one or more filters that are capable of adaptive and/or fixed operation. The filters are defined by a multiple of coefficients and the coefficients are set so as to maximize the signal to noise ratio of the receiving array's output. In one preferred embodiment, the filter coefficients are adaptively determined and are faded into a predetermined group of fixed values upon the occurrence of a specified event. Thereby, allowing the sensor array to operate in both the adaptive and fixed modes, and providing the array with the ability to employ the mode most favorable for a given operating environment. In another preferred embodiment, the filter coefficients are set to a fixed group of values which are determined to be optimal for a predefined noise environment.

Abstract: A system and process for localizing signals received on multiple co-linear arrays reduces the adverse effects on localization performance due to background noise. The system and process coherently combine all possible array cross-correlograms. The resulting correlogram is a function of two variables, one which corresponds to a fine bearing estimate and a second with maps into range.

Abstract: A radar system and method for detecting and tracking a target of interest in the presence of interference, wherein the interference emits interfering signals, includes a receiver for receiving the interfering signals directly from the interference. The receiver also receives reflected signals, wherein the reflected signals is the interfering signals reflected by the target of interest. The interfering signals and the reflected signals are compared to detect the target of interest. In one embodiment, the reflected signals and the interfering are cross-correlated. The results of the cross-correlation are used to obtain range, position, and velocity information about the target of interest from a range/Doppler map.

Abstract: An ultrasonic signal is used to link a beacon unit to a tracker unit to provide a tracking and navigation system for firefighters to use in a smoke filled environment at the scene of a fire. The beacon unit transmits an omnidirectional ultrasonic signal. The tracker unit, using a directional ultrasonic receiver provides a display or other indication of the signal strength of the received ultrasonic signal to allow the direction to the beacon unit to be determined. The ultrasonic signal provided by the beacon unit may be pulse modulated to include digitally encoded data that may be used to identify particular individuals, objects, materials, dangers, or exits. In addition, the tracker unit may be provided with a transmitter and the beacon unit provided with a receiver such that audio communication may be established therebetween.

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 wideband-to-narrowband conversion method and apparatus performs the operational step of receiving an acoustic wideband signal, initially incident on an array of acoustic wideband transducers and subsequently digitized, and in response thereto generating a spatial Wigner bilinear kernel output signal, and the operational step of receiving and spatially bandpass filtering the spatial Wigner bilinear kernel output signal to remove a wideband low frequency portion as well as any unwanted noise therefrom and retain and output only a narrowband portion thereof.

Abstract: A submarine bow dome acoustic sensor assembly comprises an outer hull bow portion, an inner pressure hull wall extending athwartships and in conjunction with the outer hull bow portion defining a free-flood compartment, and an acoustic bow panel disposed in the compartment and connected to the pressure hull wall by acoustically isolating supports. A laser scanner is disposed in the compartment and is oriented so as to project a laser beam onto a surface of the acoustic bow panel, and a sensor is disposed in the compartment and oriented so as to receive reflections of the laser beam off the acoustic panel and to transmit data from which a position of a sound generating source can be determined.

Abstract: A dual-processing interference cancelling system and method for processing a broadband input in a computationally efficient manner. Dual processing divides the input into higher and lower frequency bands and applies adaptive filter processing to the lower frequency band while applying non-adaptive filter processing to the higher frequency band. Various embodiments are shown including those based on sub-bands, broadband processing with band-limited adaptation, and broadband processing with an external main-channel generator.

Abstract: Acoustics or vibrations at a plurality of predetermined positions are respectively detected in the form of analog values, and the detected analog values are respectively converted into digital values. The digital values are subjected to digital filtering by using the digital values and filter factors, and at least one of the filter factors is changed such that the difference between the total sum of the results of digital filtering and a targeted value becomes minimum. The rate of contribution to an evaluation point is computed by using the results of digital filtering within a predetermined time when the difference becomes minimum, and the computed rate of contribution is displayed.

Abstract: The invention pertains a bathymetric sonar system involving a single swept transmit beam projector system which compensates for ship attitude and positioning changes. A sonar transducer array has a matrix of acoustic projector elements arranged in a plurality of substantially parallel rows and a plurality of substantially parallel columns; and means for causing each of the projector elements to generate an acoustic signal at a frequency and phase independently from each other projector element. Preferably the transducer array is operated by causing the projector elements to generate an acoustic signal at a frequency and phase independently from each other projector element, at a frequency and phase which is initially the same as the frequency and phase of each other element in its column and such that the frequency and phase of the projector elements in each column is different from each other column. Thus a single swept beam is projected toward the ocean floor.

Abstract: A parametric audio system having increased bandwidth for generating airborne audio signals with reduced distortion. The parametric audio system includes a modulator for modulating an ultrasonic carrier signal with a processed audio signal, a driver amplifier for amplifying the modulated carrier signal, and an array of acoustic transducers for projecting the modulated and amplified carrier signal through the air along a selected projection path to regenerate the audio signal. Each of the acoustic transducers in the array is a membrane-type transducer. Further, the acoustic transducer array is a phased array capable of electronically steering, focusing, or shaping one or more audio beams.

Abstract: A transducer is constructed of a plurality of transducer elements which are arranged in multiple layers and columns forming as a whole a generally cylindrical shape. A scanning sonar employing the transducer thus constructed can be switched between horizontal scan mode in which a vertically focused beam having a narrow horizontal beam angle (high horizontal directivity) is steered around the transducer using all the transducer elements and vertical scan mode in which a horizontally focused beam having a narrow vertical beam angle (high vertical directivity) is steered in a vertical plane directed in a specified scan azimuth to find out the angle of incidence of a received signal. The horizontally focused beam is formed by using the transducer elements of specific columns centered on the specified scan azimuth. A vertical scan signal obtained in the vertical scan mode is multiplied by a chirp signal.

Abstract: A system and method for a directional microphone system is disclosed. The directional microphone system can adaptively track and detect sources of sound information, and can reduce background noise. A first monolithic detection unit for detecting sound information and performing local signal processing on the detected sound information is provided. In the detection unit, an integrated transducer is provided for receiving acoustic waves and for generating sound information representative of the waves. A processor is coupled to the transducer for receiving the sound information and for performing local digital signal processing on the sound information to generate locally processed sound information. A base unit is coupled to the first monolithic detection unit and includes a global processor which receives the locally processed sound information and performs global digital signal processing on the locally processed sound information to generate globally processed sound information.

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: The output signals of the acoustic sensors of the antenna are subjected to a processing of the superdirective kind, with a constraint as regards the modulus and a non-linear constraint which fixes the incoherent noise reduction.The theoretical formulation of these constraints being as follows ##EQU1## the first constraint signifying that the total transfer function is a pure delay .tau., and the second constraint signifying that a limit is fixed for the incoherent noise reduction.The antenna is provided to improve the near-field reception.

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

Abstract: A phased-beam transducer is disclosed for transmitting and receiving steered acoustic beam signals that includes a sheet of piezoelectric material such as Polyvinylidene Fluoride (PVDF), a copolymer, piezo-rubber, quartz, 1-3 PZT composite, or similar transducer material. The transducer includes specially designed electrode on each side of the piezoelectric sheet. The transducer is a two channel device with a sine channel, cosine channel and a ground lead. A summing circuit is used to sum the sine and cosine channels with a 90 .degree. phase shift applied by a phase shift circuit to one of the two channels, for example, the sine channel. The transducer is designed to form a predetermined steered beam at a particular frequency. If a different sound wave frequencies are used, the transducer will form useful directional beams with different steer angles and beamwidths. Variable sector coverage is achieved by forming beams at different frequencies.

Abstract: An apparatus and method for filtering the effects of large amplitude signal fluctuations from elements of the cross-spectral density matrix of a detor array. The outputs of the array are sampled T times, and the values of each element of the matrix formed by using: ##EQU1## where Z.sub.li is the complex output of an sensor of the array at time i; Z*.sub.mi is the complex conjugate of the output of an array sensor at said time i; and k is an integer greater than 1. Because of the exponent k, small, relatively constant, terms will dominate, reducing the effect of large amplitude fluctuations. Preferably, the above value will be scaled according to: ##EQU2## which, besides being similarly filtered by the exponential terms, the resultant matrix element will have a magnitude corresponding to the actual power of the detected signal, after filtering.

Abstract: The position of an object is tracked underwater. Prior to tracking, the object is tagged with an acoustic transmitter. It is important that the transmitter emits sound waves having a frequency of at least 200 kilohertz (kHz) because it has been found that these transmitter frequencies provide better tracking data in noisy environments than conventional transmitters operating at 50-60 kHz. The acoustic transmitter is located by a split-beam transmitter. The position of the object can be accurately tracked by using two split-beam transducers, synchronization of transducer and transmitter, or echo ranging.

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: The advanced vertical array beamformer signal processor accomplishes acoustic beamforming of an underwater vertical array used in shallow water utilizing matched beam processing to suppress generated noise and/or ship radiated noise thereby increasing the detectability of a submerged source emitting only a low noise signal. The processor exploits the difference of the signal arrival angle of both active and passive signals with that of the wind generated noise and ship radiated noise which is prominent in downward refractive sound speed profiles. After filtering the undesired noise, the processor uses the depth of the source as a clue for detection; the processor is an energy detector focused on the returns of a deep source.

Abstract: A system for the detection of acoustic signals utilizing an array of acoustic sensors coupled to a beamformer which generates a steered acoustic beam using the output from one or more of the acoustic sensors within the array. The acoustic sensors include a multiaxis vector sensor co-located with a scalar acoustic pressure sensor. The beamformer generates a weighted output for each acoustic sensor by combining the weighted output of the scalar pressure sensor with the scalar field generated by forming the inner product of the vector components measured at each sensor location with a vector component weighting vector. The weighted output signals are delayed to synchronize the phase of the weighted output signal to that of a weighted signal at a reference array location. The resulting delayed weighted output signals are then summed.

Abstract: A sonar system includes a pulse generator that produces an electrical signal having a plurality of frequencies. An acoustic radiator formed as a first blazed acoustic array is arranged to be driven by the electrical signal from the pulse generator. The blazed acoustic array includes a plurality of acoustic elements rotated away from the general plane of the array. The acoustic elements are arranged to be driven by the electrical signal from the pulse generator so that they radiate a sonic field that includes a plurality of sonic frequencies with each frequency being radiated at a characteristic angle. An acoustic receiver formed as a second blazed acoustic array is arranged such that components of the acoustic field reflected from the target toward the acoustic receiver produce acoustic waves having frequencies that correspond to the angles of incidence of the reflected acoustic field components. The signals indicative of the reflected frequencies are processed to form an image of the target.

Abstract: The sonar array post processor employs an adaptive processing, known as matched beam processing, in the beam domain which takes analog or digital conventional beamforming outputs from a sonar array, multiplies them by a set of adaptive weighting coefficients and produces a new set of beams. The new output beam of highest intensity yields the ideal maximum signal gain and correct target bearing. Continuous target tracking provided by the sonar array post processor in the endfire direction of a horizontal line array minimizes the towing ships maneuvers and for, a bottom mounted surveillance system, a smaller number of arrays are required.

Abstract: A method for enhancing signal-to-noise ratio and resolution of amplitude stable signals wherein underwater acoustic data is first collected with an array of hydrophones, and then the data is digitally sampled. After producing spectra of sequential time snapshots of the digitally-sampled data, the spectra are beamformed for a single frequency. Next the low resolution beamformer response is deconvolved from the data by use of a calculated beam response pattern for the hydrophone array, so that many high-resolution estimates are created for each time snapshot. Finally, the resulting high resolution estimates are reduced to a single estimate for each spatial bin across all of the time snapshots, and the high resolution, high gain results are displayed.

Abstract: Sonar signal processing apparatus for use with an array of transducers, comprising means for reconstructing delayed time series data from an original sampled data stream.

Abstract: An adaptive system and method for reducing interference in a signal received from an array of sensors. Adaptive filters are used to generate cancelling signals that closely approximate the interference present in the received signal. The adaptive filter weights are converted into the frequency domain where the frequency representation values in a selected frequency range are truncated to avoid signal leakage involving narrow band signals. Decolorizing filters are used to produce the cancelling signals having a flat frequency spectrum. Normalized power difference is used limit the operation of the adaptive filters to the case where there is some directional interference to be eliminated.

Abstract: A broadband sonar system is configured to be coupled to a narrow band sonar sensor array having a plurality of sensor groups configured in subarrays. Each of the sensor groups within a subarray is spaced equidistantly from adjacent sensor groups within the same subarray. The sonar system includes a plurality of signal compensation filters, each being coupled to a respective one of the sensor groups for receiving signals from the respective sensor group and weighting the signals to generate respective output signals. The weighting of the signal from a first sensor group having a first SNR is greater than the weighting for the signal from a second sensor group that has a second SNR when the first SNR is greater than the second SNR, so as to maximize the SNR of the array. At least one broadband beamformer is coupled to the signal compensation filters for combining the output signals for determining ranges to targets.