Pulse or digital communications – Receivers – Automatic frequency control
Patent
1997-08-12
1998-08-04
Chin, Stephen
Pulse or digital communications
Receivers
Automatic frequency control
375326, 4551922, 4551822, H04L 2706, H04L 2722
Patent
active
057906041
ABSTRACT:
An improved automatic frequency correction acquisition system utilizes an automatic frequency correction (AFC) loop (22) having an acquisition mode in which an estimate of the frequency offset of a received carrier signal is rapidly acquired and a tracking mode in which the automatic frequency correction loop more accurately follows changes of the frequency offset. The AFC is switchable in response to predetermined control signals between the acquisition mode and the tracking mode. A carrier to impairment ratio estimator (36) is coupled with the automatic frequency correction loop (22) for estimating the carrier to impairment ratio of the incoming carrier signal. An automatic frequency correction controller (30) is coupled with the automatic frequency correction loop (22) and with the carrier to impairment ratio estimator (30) and is responsive to the carrier to impairment ratio estimate being at or above a preselected threshold value for producing a tracking control signal (24) comprising one of the predetermined control signals. The automatic frequency correction loop (22) is responsive to the tracking control signal (24) for switching from the acquisition mode to the tracking mode.
REFERENCES:
patent: 4941155 (1990-07-01), Chuang et al.
patent: 5471508 (1995-11-01), Koslov
patent: 5579338 (1996-11-01), Kojima
Gurney David Paul
Kelton James Robert
Mannette Michael Russel
Chin Stephen
Deppe Betsy L.
Gavrilovich Charles D.
Motorola Inc.
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