A robust and fast-locking all-digital carrier recovery loop for QAM signals

The authors present the design and the implementation of an all-digital carrier recovery loop for quadrature amplitude modulation (QAM) signals. Original features concerning the programmability of the loop, its fast-locking properties in acquisition and restart procedures as well as its wide acquisition range are discussed. The emphasis is on its performance in terms of robustness versus noise and intersymbol interference and protection against potential frequency false-locks. Experimental results are reported for a 16-QAM system