Hybrid tracking loop for detecting phase shift keyed signals

Details Hybrid tracking loop for detecting phase shift keyed signals Hybrid tracking loop for detecting phase shift keyed signals

1975-09-29

1976-09-28

Grimm, Siegfried H.

Demodulators

Amplitude modulation demodulator

Having specific distortion, noise or other interference...

325349, 325419, 329136, 331 17, H03D 300

Patent

active

039835014

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. The filter is initially broadband to allow detection of doppler shifted carrier signals and after locking onto the carrier signal it is switched to a narrow bandwidth to permit detection of low signal to noise ratio signals. A switching circuit is also provided to eliminate cycle slipping or loss of lock during periods when there is a phase shift in the received signals.

REFERENCES:
patent: 3753114 (1973-08-01), Burley
patent: 3883806 (1975-05-01), DeLong et al.
patent: 3906376 (1975-09-01), Bass

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