Pulse or digital communications – Repeaters – Testing
Patent
1993-04-27
1994-05-10
Chin, Stephen
Pulse or digital communications
Repeaters
Testing
375 97, 3647242, H04B 304, H04L 2706
Patent
active
053115465
ABSTRACT:
A method and apparatus are provided for adaptively equalizing data signals in a communications receiver. An unequalized data signal is demodulated. The demodulated data signal is filtered in an adaptive equalizer that initially updates adaptive filter coefficients using error signals derived from a first algorithm. A carrier lock signal is generated when a phase error of a filtered signal output from the adaptive equalizer reaches a threshold value. The adaptive filter coefficients are updated using error signals derived from a second algorithm instead of the first algorithm in response to the carrier lock signal. The first algorithm is a self-recovering equalization algorithm such as the Constant Modulus Algorithm. The second algorithm can be a decision directed algorithm. Carrier phase is recovered without the use of a phase rotator or phase de-rotator, by locating the adaptive equalizer inside of the carrier recovery loop. The invention is particularly adapted for use in the recovery of multilevel amplitude modulated data, such as QAM data.
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Lery Scott A.
Paik Woo H.
Tom Adam S.
Chin Stephen
General Instrument Corporation
Lipsitz Barry R.
Shankar Vijay
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