False carrier lock receiver and associated methods for detection

Details False carrier lock receiver and associated methods for detection False carrier lock receiver and associated methods for detection

1999-06-30

2000-10-17

Mis, David

Demodulators

Phase shift keying or quadrature amplitude demodulator

329306, 329310, 375261, 375326, 375329, 375344, H03D 300, H04L 2738, H03L 7095

Patent

active

061337854

ABSTRACT:
A receiver includes a demodulator and a false carrier lock detector circuit for a quadrature amplitude modulated (QAM) signal. The demodulator includes a controllable oscillator and an offset frequency generator for generating an offset frequency for the controllable oscillator to lock to a carrier of the QAM signal. The demodulator is susceptible to false carrier locking responsive to the offset frequency being substantially equal to the symbol rate divided by four or an integer multiple thereof. The receiver further includes the false carrier lock detector circuit including a first detector for detecting consecutive symbols spaced 180.degree. apart, and a second detector for determining whether an intervening sample between the consecutive symbols is outside a predetermined distance from the origin. The first and second detectors cooperate to determine false carrier locking based upon the intervening sample being outside a predetermined distance from the origin.

REFERENCES:
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patent: 5519356 (1996-05-01), Greenberg
patent: 5784686 (1998-07-01), Wu et al.
patent: 5838737 (1998-11-01), Yamaguchi et al.

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