Abstract: A low frequency sonar system for detecting buried cables and pipelines that includes at least three sub-bottom sonar beam projectors arranged athwarships, i.e. transverse to the central longitudinal axis of the system platform and a common receiver, the latter preferably being an arc focused device. The projectors are comprised of parametric transmitters, with the two outer projectors canted relative to the middle projector so that sonar return signals having a relatively narrow beamwidth are directed to the bottom and returned as a sequence of specular reflections along the length of sub-bottom targets to the common receiver. The transmission from the three parametric transmitters result in three spaced apart "hits" on the target which are displayed as a function of depth. Three detections in a row, i.e. at the same depth, provide an indication of a cable or pipeline buried beneath the bottom of a body of water.

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 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.

Abstract: An apparatus for measuring velocity relative to a reference plane having a linear sonar array disposed in parallel with the direction of travel and including from the foremost position to the rearmost position a first transmitter, a plurality of first receivers, a second transmitter, and a plurality of second receivers. The second transmitter is controlled to transmit a sonar pulse after a predetermined time delay has lapsed since the first transmitter transmitted a sonar pulse. The predetermined time delay is selected such that the second transmitter transmits the sonar pulse when the second transmitter occupies the position which the first transmitter occupied when it transmitted the first sonar pulse.

Abstract: A synthetic aperture side-looking sonar which includes a receiver transducer array and two transmitter transducers. When the apparatus is at a first position, the forwarded transmitter transducer is provided with a signal of frequency F1 while the aft transmitter transducer is provided with a signal of frequency F2. At a subsequent position, the application of the frequencies to the transmitter transducers are reversed. At each location, the F1 and F2 returns are stored and combined with the returns of the subsequent transmission to form a plurality of receiver beams.

Abstract: A sonar system wherein sum and difference beam patterns are generated utilizing a plurality of transducer elements arranged in a line array. Receiver apparatus including a receiver transducer also constituted as a line array perpendicular to the transmitter transducer is used to form sum and difference receiver beams and return signals are processed so as to accurately define the azimuth as well as elevational position of a target within a target area.

Abstract: A high speed multibeam sidelooking sonar system for processing acoustic signals including a transmitter for transmitting acoustic energy, and a hydrophone array for receiving reflected acoustic energy transmitted by the transmitting means and forming an ensonification region, including a plurality of hydrophone elements spaced at a predetermined distance. The transmitter includes a plurality of transmit transducers operating at different frequencies to divide the ensonification region into ensonification strips, such that the predetermined distance between the plurality of hydrophones is maximized. Therefore, the performance of the high speed multibeam sidelook sonar system is maximized at minimum range. Further, the high speed multibeam sidelook sonar system as described above minimizes fill time degradation with the plurality of transmit transducers, which increases range resolution and acoustical performance of the high speed multibeam sidelook sonar system at the minimum range.

Abstract: Side looking sonar apparatus on a carrier vehicle obtains an acoustic picture of a target area below the vehicle from some minimum range out to some maximum range on either side of the vehicle. An angle look sonar obtains an acoustic picture within the gap portion between the minimum range points of the side looking sonar. Signals are obtained indicative of the heading of the vehicle as well as its actual direction of motion. These signals are utilized to generate a crab angle signal which is utilized to rotate the angle look sonar apparatus to the proper orientation for obtaining complete bottom coverage even when the carrier vehicle is crabbing due to a cross current.

Abstract: A focused arc transducer which lies on an arc of a circle having a radius of curvature R is used as the transmitting transducer in a side looking sonar system. The arc lies in a plane which is tilted slightly with respect to a vertical orientation and the apparatus as utilized at an altitude H above a target area wherein H in one embodiment is greater than the radius of curvature and in another embodiment where it is less than the radius of curvature. This operation results in a desired trapezoidal insonification pattern on the target area with the pattern at maximum range being a little wider than the collective width of a plurality of receiver beams for a multibeam system.

Abstract: A side-looking sonar system utilizing an extremely long arc transducer for ultra high resolution work. The transducer is made up of a plurality of segments each connected to signal processing apparatus which electronically varies the focus of the transducer as a function of time as well as a function of transducer altitude above a target area. Additional beams, parallel to a center beam, may be formed to give the system multi-beam capability for increased search rates.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A side looking sonar system having a transducer made up of a plurality of active transducer element sections lying along a line and wherein the element sections are relatively phased to provide for all range focusing and multiple beam formation. The element sections are longer in the middle of the transducer and reduce in length toward the ends of the transducer. In one case the line is an arc lying in a plane, with the plane having a certain depression angle.

Abstract: A synthetic aperture side-looking sonar system wherein beam formation takes place in two stages, the first being real aperture multiple beam formation and then coherent addition of real aperture beams to obtain the synthetic aperture improvement.

Abstract: An underwater scene is viewed by a TV camera which in place of the conventional blue, green and red filters has three filters with transmission characteristics within the range of colors passed by the water medium, typical filters being blue-green, green, and yellow-green. The three TV signals from these signals are used to energize the conventional blue, green and red guns of a color TV cathode ray tube (CRT).

Abstract: A depth sounder in which the transducer beam is in the form of a section of hollow cone. With the hollow conical beam, the slant range to the bottom in all directions is the same and minimum depth determination over a path width of 2 to 4 times the depth of the water may be made.

Abstract: Apparatus which automatically detects targets of interest in line scanned amplitude modulated data systems such as side scan radar or sonar. The apparatus examines a received signal for certain predetermined parameters. On the basis of values of these parameters a probability code is developed which is a measure of the probability that a target is present. The signal which is divided into a corresponding number of range cells, is rewarded if a target like signal occurs within a certain number of resolution cells of the same range on the next signal. If no target like features are present in this zone on the next signal, a penalty is applied.

Abstract: A high resolution side-looking sonar system wherein the focus is electronically varied with range such that any and all returns are in focus. Focusing is accomplished by time varying phase cancellation, the apparatus additionally forming multiple receiver beams for increasing search rate.