Abstract: A continuous wave, doppler sonar has an underwater towed portion including projector disposed vertically displaced from a multi-element receiving array. Received CW signals are processed for spillover elimination and subjected to phase lock loop tracking filters for reverberation and target doppler prior to target signal detection, thresholding, multiplexing and transmission to the towing portion. The target signals are distributed as to azimuth, recirculated in a memory, and reiteratively displayed in PPl format, with periodic updating.

Abstract: A doppler compensated sonar systems is disclosed as containing one or more ata processing channels connected through a multiplexer to a like plurality of piezoelectric elements in a reversible electro-acoustical transducer. Each channel thereof includes a transmitter and a receiver, the latter of which includes signal perfecting circuitry and a pair of effectively series connected phase lock loops constituting reverberation and target doppler tracking filters, respectively. Hence, each of said channels effectively process received target signals without any adverse doppler effects being present therein which are then, in turn, read out by any suitable video display. When mounted on a fast moving vehicle, the subject doppler compensated sonar system optimizes the avoidance of hazardous or other objects that may occur in the path thereof.

Abstract: A dual frequency, synthetic aperture, sonar system includes a transmitter r projecting insonifying pings alternatively at first and second frequencies and a linear receiving array carried by a vehicle so as to receive returns from said pings. The first and second frequency returns are separated and subjected to processing in parallel channels where they are resolved into in-phase and quadrature components for subsequent phase-error correction, coherent addition, and synthetic aperture beamforming.