Communications – electrical: acoustic wave systems and devices – Distance or direction finding – With beam steering – scanning – or focussing
Reexamination Certificate
1982-11-17
2001-10-30
Pihulic, Daniel T. (Department: 3662)
Communications, electrical: acoustic wave systems and devices
Distance or direction finding
With beam steering, scanning, or focussing
Reexamination Certificate
active
06310832
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a steerable beamformer for a sonar system and more particularly to a steerable beamformer which utilizes solid state components to form and steer the sonar beam so that tracking of a sonic emitter may be achieved without any mechanically moving components.
The preferred embodiment of the invention will be described as a replacement for a tracking sonar which uses a mechanical scanning element to make selective contact with the acoustic transducers substantially uniformly distributed over a spherical surface. The spherical surface typically has greater than 1200 transducers of which the mechanical scanner makes contact with greater than 200 elements. The desire for making a smooth transition between the electrical contacts of adjacent transducers while avoiding transients produced by the switching from one transducer to another within the mechanical scanner makes it necessary to utilize complex brush arrangements with small mechanical tolerances thereby resulting in great expense for the fabrication of such a mechanical scanning device. In addition, the mechanical scanner requires considerable volume which in some sonar applications is at a premium and could be better utilized, as in this invention, by providing a space for the electronic components of the sonar system. Finally, the mechanical scanner requires highly skilled maintenance personnel and repairs can only be made at base facilities specially equipped for this purpose.
It is therefore an object of the present invention to provide a solid state tracking system instead of a mechanical scanner. It is a further object of the invention to provide a tracker which has smooth and accurate beam steering with the absence of transients produced by the transfer to adjacent transducers during the process of moving the tracking beam.
It is a further object of the invention to maintain accurate depression/elevation steering at angles where the mechanical scanner starts to lose contact with transducers because of the truncation of the transducers on the sphere at large depression or elevation angles. It is a further feature of the invention that a relatively small volume and low power are required relative to the mechanical scanner.
Another major feature is the absence of special maintenance requirements since repair is done at the electronic module level which requires electronic technician skills readily available onboard ships.
SUMMARY OF THE INVENTION
A beamformer is described in which the transducers are uniformly arranged in horizontal rows on a spherical surface. Each adjacent transducer of a row provides in parallel a signal to a corresponding adjacent storage stage of a charge coupled type shift register. The shift register has a predetermined number of adjacent stages corresponding to the number of transducers within the array forming the beam which stages are gated into a beamforming circuit which provides a left half and a right half fan shaped beam in the direction transverse to the row. The azimuthal direction of the fan shaped beams is determined by a gating signal occuring at the appropriate time as the shift register information is shifted past the beamforming circuitry to select the azimuthal group of transducers whose signals, when beamformed, will produce a beam in the desired direction. Interpolation between adjacent fan shaped beams of a row is obtained by generating two adjacent fan shaped beams, each having a left half beam and a right half beam. Each corresponding half is multiplied by a quantity “A” and “(1−A)” respectively and added to cause the resulting interpolated left and right half fan shaped beams to have their main response axis on the signal source within the angle between the adjacent fan shaped beams and to make transitions between adjacent beams without transient electrical effects. The right and left half beam signals from a signal source provided by the interpolated beams of all rows within the array have the same azimuthal direction and are provided to declination/elevation beamformers in which the right half beam signals provide an upper right half beam and a lower right half beam signal. Similarly, the left half beam provides an upper left half beam and a lower left half beam signal. The output signals of these four quadrant beams from a target signal generate up/down and left/right error signals which are provided as inputs on the tracking circuitry and determine the direction of the quadrant beams.
REFERENCES:
patent: 3302204 (1967-01-01), Mathes
patent: 3307141 (1967-02-01), Saxton et al.
patent: 3555500 (1971-01-01), Longerich et al.
patent: 3750152 (1973-07-01), Waful
patent: 3821740 (1974-06-01), Ehrlich
patent: 3906431 (1975-09-01), Clearwaters et al.
patent: 4001763 (1977-01-01), Kits van Heyningen
Daly,Crowley & Mofford,LLP
Pihulic Daniel T.
Raytheon Company
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