Carrier recovery system using acquisition and tracking modes and

Details Carrier recovery system using acquisition and tracking modes and Carrier recovery system using acquisition and tracking modes and

1993-08-20

1995-11-28

Chin, Stephen

Pulse or digital communications

Receivers

Automatic frequency control

375261, 4552263, H04L 2706

Patent

active

054715083

ABSTRACT:
A carrier recovery system for use in illustratively a passband QAM (quadrature amplitude modulation) demodulator (10) and specifically such a system, including apparatus and accompanying methods, that employs separate acquisition and tracking modes and automatic carrier-to-noise estimation. In particular, a carrier recovery system (200) is operated in two modes: an acquisition mode to first attain an initial carrier lock, during which simplified reduced constellation slicing is used to determine a quadrant of each incoming symbol; and a tracking (or lock) mode, during which full slicing is used, to accurately track variations in frequency and phase that may occur to a carrier while the system remains locked. The mode changes based upon whether, e.g., the average error energy associated with fully sliced symbols is greater than or less than a pre-defined switching threshold value. The value of the switching threshold changes in a pre-determined manner with changes in noise content, particularly a carrier-to-noise ratio (CNR), of the received symbols. Two appropriately spaced switching threshold values, one for use in each mode, can be used to provide enhanced operational stability. An implementation of a QAM CNR estimator circuit (800) is also provided.

REFERENCES:
patent: 4227152 (1980-10-01), Godard et al.
N. K. Joblon, "Joint Blind Equalization, Carrier Recovery, and Timing Recovery for High-Order QAM Signal Constellations", IEEE Transactions on Signal Processing, vol. 40, No. 6, Jun. 1992, pp. 1383--1398.
N. K. Jablon, Joint Blind Equalization, Carrier Recovery, and Timing Recovery for 64-QAM and 128-QAM Signal Constellations, Record of IEEE International Conference on Communications (Boston, Mass.), Jun. 11-24, 1989 pp. 1043-1049.
A. Benveniste et al., "Blind Equalizers", IEEE Transactions on Communications, vol. COM-32, No. 8, Aug. 1984, pp. 871-883.

Affiliated with

Also associated with

Rating

Carrier recovery system using acquisition and tracking modes and does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Carrier recovery system using acquisition and tracking modes and, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Carrier recovery system using acquisition and tracking modes and will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2019352