George A. Gilmour

Side‐looking sonar beam forming utilizing the chirp Z‐transform

Apparatus which generates a plurality of sets of radially extending beams in a chirp Z-transform sonar beam former. Only a particular beam from each set is chosen for display.

Spotlight-mode synthetic aperture side-look sonar

A side-look sonar system and method apply a spotlight-mode synthetic aperture technique to provide increased image resolution and a long receive aperture. A control circuit activates mechanical drives to rotate projecting and receiving sonar transducers as the carrier vehicle on which the transducers are mounted moves relative to a target. The mechanical drives rotate the transducers as a function of the rate of movement of the carrier vehicle to direct receiving and projecting surfaces of the transducers at the target for an extended period of time. An image processor uses conventional beamforming techniques to form a high resolution image of the target based on the acoustic energy samples acquired by the receiving transducer.

Sonar beam forming utilizing the chirp Z-transform

The chirp rate in a chirp Z-transform sonar beam former is varied as a function of range to form beams in the near field. The chirp rate may be varied with each range cell under examination or with each group of range cells.

Passive fiber optic sonar system

A fiber optic sonar system wherein first and second optical fibers are wound on a common mandrel and provided with a light energy beam. An acoustic signal differentially varies the index of refraction of the optical fibers to result in an interference pattern dependent upon the frequency of the received acoustic signal or signals. The apparatus is operable to form one or more hollow conical receiver beams.

Scanning beamformer for a very high resolution circular arc sonar

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.

Development to high‐resolution side‐look sonar

About 28 years ago, the Navy had a requirement to scan the bottom of channels and harbors with sufficient resolving power to identify minelike objects on the bottom with cylindrical dimensions 112 in. in diameter by 6 in. long. A side‐scan sonar was designed to provide a narrow fan shaped beam focused on a line on the bottom by means of a fixed arc array. The transducer array had to be towed a fixed distance (the radius of curvature of the arc array) off of the bottom for optimum focus. The system scanned the bottom by means of the vehicle movement in the direction of tow and perpendicular to the direction of tow by the travel time of the acoustic signal emitted from the transducer to the bottom. This system had a number of limitations: bottom coverage rate (m2/h), fixed height above the bottom, a limited display capability, and limited signal processing. These led to the development of multibeam arrays with electronic all‐range focusing, CRT displays, and adaptive time varied gain tied into the backgroun...

Hybrid focusing for side‐look sonar

Two focusing principles are presently used in high performance (0.1° beamwidth) side‐look sonars (SLS), the mechanical arc, and electronic all‐range focusing. Hybrid techniques to combine the two principles are described in this paper. Focusing is partially accomplished using the mechanical are principle, then completed electronically. This can be thought of as a vernier to allow a mechanical arc SLS to be flown at an altitude other than the radius of curvature. Alternatively, it can be considered to be a way to expand the depth of field of a mechanical arc, or to restrict the depth of field of electronic focusing. The techniques described best fit a very high resolution SLS, e.g., 0.05° beamwidth, the requires only about three parallel beams per side.