Pulse or digital communications – Receivers – Automatic frequency control
Patent
1994-10-26
1996-07-02
Chin, Stephen
Pulse or digital communications
Receivers
Automatic frequency control
375329, 375360, 375375, H04L 2706
Patent
active
055330690
ABSTRACT:
A carrier sensing circuit coupled to a receiving amplifier, measures the frequency of a phase shift modulated carrier signal by counting a predetermined number of the pulses for a measured interval whose duration is determined by counting a first clock count value. A demodulator coupled to the amplifier, detects when the spacing between the edges of the square wave pulses changes in response to the phase shift modulation. The demodulator measures first intervals between consecutive rising edges of the received signal, by counting clock pulses for a second selected interval whose duration is determined by a second selected count value. The demodulator further measures second intervals between consecutive falling edges of the received signal by counting clock pulses for a third selected interval whose duration is determined by a third selected count value. A compensating circuit coupled to the carrier sensing circuit and to the demodulator, compensates for frequency drift in the carrier signal or in the local oscillator by adjusting the second selected count value and the third selected count value, using the first clock count value.
REFERENCES:
patent: 4707666 (1987-11-01), Pfeifer et al.
patent: 5272448 (1993-12-01), Hedstrom et al.
Bracco Michael J.
Camp, Jr. William O.
Fleek Arthur E.
Warchocki Gary M.
Chin Stephen
Hoel John E.
International Business Machines - Corporation
Keohane Stephen T.
Kim Kevin
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