Pulse or digital communications – Receivers – Automatic frequency control
Patent
1994-11-22
1996-02-27
Chin, Stephen
Pulse or digital communications
Receivers
Automatic frequency control
375331, 4551641, 329306, H04L 2706
Patent
active
054955068
ABSTRACT:
An automatic frequency control apparatus includes a frequency converter, an analog/digital converter, extractor, a storage unit, a controller, and a local oscillator. The storage unit stores unique word frequency modulation models representing time waveforms obtained by modulating, with a unique word, three frequencies which are a frequency equal to that of a desired intermediate-frequency signal, a frequency slightly higher than that of the desired intermediate-frequency signal, and a frequency slightly lower than that of the desired intermediate-frequency signal. The controller performs a cross correlation calculation between the intermediate-frequency signal of the unique word component from the extractor and all the unique word frequency modulation models stored in the storage unit, corrects an error of a control signal set in correspondence with a reception channel on the basis of a signal representing a unique word frequency modulation model corresponding to a maximum correlation calculation value, and outputs the control signal. The local oscillator supplies, to the frequency converter, a local oscillation frequency corresponding to the control signal from the controller.
REFERENCES:
patent: 5020131 (1991-05-01), Isoe
patent: 5148451 (1992-09-01), Otasi et al.
patent: 5276210 (1994-01-01), Iwasaki
patent: 5363415 (1994-11-01), Iwasaki
patent: 5376894 (1994-12-01), Petranovich
Chin Stephen
NEC Corporation
Webster Bryan E.
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