Patent ID: 6133785
Filing Date: 2000-10-17
Classification: H04L

Abstract:
A receiver for a quadrature amplitude modulated (QAM) signal comprising:a demodulator for generating, from the QAM signal, received symbols about an origin at a symbol rate, said demodulator comprising a controllable oscillator and an offset frequency generator for generating an offset frequency for said controllable oscillator to lock to a carrier of the QAM signal;said demodulator being 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; anda false carrier lock circuit comprising a first detector for detecting consecutive symbols spaced 180.degree. apart, and a second detector cooperating with said first detector for determining false carrier locking further based upon an intervening sample between the consecutive symbols being outside a predetermined distance from the origin.