A wideband carrier-recovery system for multilevel QAM signals

A decision-directed carrier-recovery technique for coherent demodulation of quadrature amplitude modulated (QAM) signals is proposed. This system adaptively tracks both the carrier frequency and phase of the received QAM signal´s modulated carrier. The acquisition time of the proposed system is shown to be faster than that of conventional carrier-recovery schemes, especially when the initial carrier-frequency offset is relatively large, i.e. beyond a small fraction of the symbol rate. Also, the proposed method has a wider acquisition range compared to conventional techniques