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.

Circularly symmetric, zero redundancy, planar array having broad frequency range applications

An array transducer ultrasound beamformer (300) includes a plurality of processing channels, one for each active element of the transducer array (300). Each channel includes a digitizing unit (330) for converting the received signal to digital samples and a time multiplexed delay unit (340) for producing a primary stream of delayed TDM samples corresponding to one or more beams. Within each channel, the primary stream of delayed TDM samples is demultiplexed (360) in order to separate the stream in a plurality of secondary streams of delayed TDM samples, wherein each of the secondary streams corresponds to a portion of a beam or a single beam.

Digital ultrasound beamformer

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

Method and apparatus for random array beamforming

An apparatus and a method that achieve physical separation of sound sources by pointing directly a beam of coherent electromagnetic waves (i.e. laser). Analyzing the physical properties of a beam reflected from the vibrations generating sound source enable the reconstruction of the sound signal generated by the sound source, eliminating the noise component added to the original sound signal. In addition, the use of multiple electromagnetic waves beams or a beam that rapidly skips from one sound source to another allows the physical separation of these sound sources. Aiming each beam to a different sound source ensures the independence of the sound signals sources and therefore provides full sources separation.

Sound sources separation and monitoring using directional coherent electromagnetic waves

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.

Sonar array post processor

An ambient sea noise elimination system is disclosed in which the outputs of a directional hydrophone and an omnidirectional hydrophone are filtered and summed such that the effective receiving pattern below approximately 300 Hz is a vertically oriented dipole pattern having a null in the horizontal direction and such that the effective receiving pattern above 300 Hz is a cardioid having its null either pointing upwardly or pointing downwardly in a vertical direction. The option of simple omnicoverage at the high frequencies can also be easily implemented. This system thus takes advantage of the discovery that ambient sea noise under 300 Hz primarily travels in a horizontal direction whereas ambient sea noise above 300 Hz generally travels in a vertical direction. Signal separation is accomplished by a low pass filter connected between the directional hydrophone and a first summing circuit whereas the cardioid receiving pattern is derived by summing the outputs of high pass filters interposed respectively, between the directional hydrophone and a second summing circuit, and between the omnidirectional hydrophone and this second summing circuit. The output of the second summing circuit is coupled as one input to the first summing circuit along with the output of the low pass filter such that the output of the first summing circuit provides acoustic signals having ambient sea noise substantially removed therefrom. For omnicoverage above 300 Hz, a simple high pass filter on the omnichannel is sufficient.

Ambient sea noise elimination method and apparatus

Discrimination of long range targets from short range targets is provided by generating a vertical dipole beam and a narrow uni-directional horizontal beam which may be steered. Targets in the dipole beam are short range targets whose acoustic signals arrive at angles to the horizontal plane, whereas long range targets are those in the horizontal beam, since acoustic signals from long range targets come in on the horizontal plane.

Range determining system

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.

Element-sited beamformer

In order to sense the presence of sound in a remote underwater location, a neutrally buoyant reflector (20) is deployed underwater, and a laser (12) disposed at a remote location aims coherent light at the reflector (20). A detector (24) senses the coherent light reflected from the reflector (20) and compares it in phase with coherent light split from the outgoing beam. The system then provides an indication of the presence of sound by, for instance, amplifying the result of the phase detection to a speaker (26).

Samuel S. Ballard

Papers

Ambient sea noise elimination method and apparatus

Range determining system

Element-sited beamformer

Laser sound detector