Abstract: A crystal oscillator that is temperature compensated by digitally substrang a correction frequency from the running frequency of the crystal oscillator to provide the required operating frequency. The correction frequency is generated by a digital frequency synthesizer circuit which is controlled by the output of a programmable read-only memory which has been programmed to generate the required correction frequency for each temperature code over the operating temperature range. The temperature code is generated by gating a digital counter with the output of a monostable multivibrator which utilizes a thermistor to make its gate interval proportional to temperature.

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.

Abstract: A phase shift keyed (PSK) pulse synthesizer which is part of an acoustic transmitter located in an underwater vehicle to provide identification and tracking of the vehicle as well as telemetry data when used on an instrumented underwater tracking range. The synthesizer is synchronized with the range time standard and generates phase coded pulses in a format suitable for input to an amplifier. A timing circuit divides a high frequency clock to produce square wave outputs at the desired frequency. A programmed read only memory (PROM) contains the identification code and is addressed from the timing circuit. A phase shift modulator combines the desired frequency with signals from the PROM and from a telemetry data generator to provide the amplifier with a digital analog of the desired acoustic message to be transmitted.

Abstract: A hybrid tracking loop detector system that accurately demodulates phase ft keyed acoustic telemetry signals. The system internally determines the received carrier frequency and detects phase shifts that denote the digital format depicted by the phase shift keyed signals. The system is particularly useful for operating at low signal to noise ratios and with relatively short messages. The detector includes a phase lock loop comprising a phase comparator, an amplifier, an adjustable filter and a voltage controlled oscillator. The phase and frequency of the oscillator are divided and are locked to the carrier frequency of the received signal and are used as a reference for the phase comparison detection. The system has two sequented modes of operation, a direct acquisition mode and a holding mode. The detector switches automatically from the direct acquisition mode to the holding mode.

Abstract: A target simulator system that may be suspended in the ocean to simulate a oving target to a homing weapon. The system includes a receiving transducer for receiving an acoustic signal transmitted by the homing weapon. The acoustic signal is then amplified, doppler shifted, filtered and then retransmitted by a transmitting transducer to the homing weapon. The doppler shift may be selected to have the retransmitted signal simulate a target that is moving towards or away from the homing weapon. The system includes a power compensating circuit and a monitor circuit to assure that the target simulator system is operating within acceptable amplification limits.