Abstract: A modulation/signal processing technique for acoustic communication in show water. Digital information is transmitted in a time expended version of frequency shift keying where a tone burst at a first frequency represents a logical zero and a tone burst at a second frequency represents a logical one. There is a long quiet time between bits to allow multipath interference to decay. A relative energy detector with a fast attack/slow decay circuit for Doppler compensation is used to receive the transmitted tone bursts and reproduce a digital data train equivalent to the transmitted pulse train. A single communication channel employs two frequencies to transmit an identity code as a signal validating and identification method and two frequencies to simultaneously transmit telemetry data.

Abstract: An inertial measurement underwater tracking system which determines range sition onboard an underwater vehicle using inertial navigation techniques. The system uses acoustic telemetry to relay the range position from the vehicle to an operations site. The position data is also recorded onboard the vehicle for post-run analysis. An onboard computer receives the inertial measurements from an inertial measurement unit and computes vehicle position with respect to an initialized reference. An acoustic transmitter receives the measurements, formats the data and transmits it by acoustic telemetry. An underwater hydrophone receives the acoustic telemetry and inputs the data to an acoustic processor to reconstruct the original position data. A range computer processes in real-time the data, and displays and records the time history of vehicle location on the range. After recovery the onboard recorded data is played back into the range computer to provide a maximum accuracy, continuous vehicle-run history.

Abstract: A Doppler compensated PSK signal processor which receives a plurality of sages from a sensor array and decodes each message for further data processing. The signal processor compensates for the Doppler shift in the message frequency due to the velocity differential between the transmitting vehicle and the sensor array. The message is decoded for a valid identification code from which is derived a time mark related to a specified system time to provide range and direction information for the identified transmitting vehicle. The telemetry data in the message and the time mark are output to a data processing system on an interrupt basis to provide tracking and data analysis for the transmitting vehicle.