Pulse or digital communications – Receivers – Automatic frequency control
Patent
1997-04-09
1998-09-29
Chin, Stephen
Pulse or digital communications
Receivers
Automatic frequency control
375375, 375343, 329307, H04L 2706
Patent
active
058155350
ABSTRACT:
A carrier recovery apparatus includes a loop filter that converges quickly and corrects a large frequency error. The carrier recovery apparatus includes a multiplier, a matched filter, a phase error detector, a loop filter and a numerically controlled oscillator (NCO). A bandwidth varying circuit varies the bandwidth of the loop filter according to whether the signal output from the matched filter is phase-locked. A frequency error detector detects a frequency error from the output of the matched filter. An adder adds each level of an input sweep signal and the output of the loop filter, and supplies the added results to the NCO. A switch selectively supplies the output of the loop filter to the adder. A controller generates a sweep signal having a plurality of levels and controls turning the switch on and off. The controller supplies the sweep signal having the plurality of levels to the adder during the time when the switch is turned off, to determine the level of the sweep signal when the output of the frequency error detector becomes zero, and supplies the level of the determined sweep signal to the adder during the time when the switch is turned on. The carrier recovery apparatus can recover an optimal carrier from the received signal.
REFERENCES:
patent: 3878334 (1975-04-01), Halpern
patent: 4672637 (1987-06-01), Halpern et al.
patent: 4860321 (1989-08-01), Von Der Embse
patent: 4916405 (1990-04-01), Keate et al.
Choi Jang-jin
Choi Yang-seok
Chin Stephen
Samsung Electronics Co,. Ltd.
Yu Frederick
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