Pulse or digital communications – Repeaters – Testing
Patent
1983-08-26
1985-05-07
Safourek, Benedict V.
Pulse or digital communications
Repeaters
Testing
328134, 329104, 329110, H03D 318
Patent
active
045162506
ABSTRACT:
A frequency and phase comparator circuit for determining the frequency difference between a reference signal of a known frequency and a variable signal of unknown frequency. The subject circuit monitors the two signals and detects the occurrence of phase shifts between the two signals. In particular, this circuit detects phase shifts of 180 degrees and 360 degrees and records a full slip indication with each occurrence of a 360 degree phase shift. These phase shifts indicate that at some point in time during transmission, the two signals were out of phase and not of exact frequency. In addition, the subject circuit provides a direction of drift indication with each 180 degree shift. These direction indications are output following a 360 degree phase shift or full slip and are determinative of the relative frequencies of the two signals by designating whether the frequency of the variable signal is higher or lower than that of the reference signal over the duration of the full slip. Appropriate adjustments may then be rendered to adjust the frequencies.
REFERENCES:
patent: 3543177 (1970-11-01), Chang
patent: 3663884 (1976-05-01), Pattantyus
patent: 3766484 (1973-10-01), Morris et al.
patent: 3947775 (1976-03-01), Thiebaut
patent: 4012598 (1977-03-01), Wiley
patent: 4264866 (1981-04-01), Benes
patent: 4378509 (1983-03-01), Hatchett et al.
"A Cycle Slip Detector for Phase Locked Demodulators", IEEE Transactions on Instrumentation and Measurement, F. M. Gardner, vol. IM-26, No. 3, Sep. 1977, pp. 251-254.
AT&T Information Systems
Duft D. M.
Safourek Benedict V.
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