An IF carrier recovery loop using decision feedback for a 16-QAM demodulator

A carrier recovery loop based upon decision-directed IF remodulation techniques is presented. The 16-QAM signal is converted into a 3-ary ASK signal containing a discrete carrier component, which can be tracked by a phase-locked loop. The symbol timing recovery is accomplished by a coherent early-late tracking loop, which uses decision feedback as well. Thus, the carrier recovery, the symbol timing recovery, and the data detection are strongly interrelated processes, each being of vital importance for the correct demodulation of the received 16-QAM signal.<>