Automatic noise normalization and reacquisition control for a QP

Details Automatic noise normalization and reacquisition control for a QP Automatic noise normalization and reacquisition control for a QP

1995-06-19

1996-10-15

Chin, Wellington

Pulse or digital communications

Synchronizers

Synchronizing the sampling time of digital data

375344, 375345, H04L 700

Patent

active

055662145

ABSTRACT:
A QPSK demodulator symbol tracking loop including automatic noise normalization and reacquisition control enables improved symbol tracking and acquisition during fading or intermittent channel conditions. A noise variance estimate is determined and the symbol tracking loop flywheels when the signal level dips below a flywheel threshold relative to the noise variance estimate during fading or intermittent channel conditions. Determination in advance of an absolute power level of the thermal noise floor of analog front end components is dispensed with and precise control of the gain and noise level of the analog front end components is not needed, thus simplifying design. A reacquisition mode is declared upon determination of an abrupt increase in signal level indicative of emergence from a fading condition or upon detection of an excessive symbol tracking error signal. During the reacquisition mode, the loop gain of the symbol tracking loop is temporarily increased to improve reacquisition time.

REFERENCES:
patent: 4472817 (1984-09-01), Poklemba et al.
patent: 4724486 (1988-02-01), Tonge et al.
patent: 5307165 (1994-04-01), Kawashima et al.
patent: 5440587 (1995-08-01), Ishikawa et al.
"Telecommunication Systems Engineering" by William C. Lindsey et al, pp. 428-435, Prentice-Hall, Inc., New Jersey 1973.

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