MAXIMUM-LIKELIHOOD CARRIER PHASE RECOVERY FOR COHERENTLY ORTHOGONAL CPFSK SIGNALS

ML estimation of carrier phase for coherently orthogonal CPFSK signals is considered. While the estimator is in general non-implementable, its high and low SNR approximations both lead to linear, readily implementable receiver structures. The high SNR approximation yields a DA receiver, while the low SNR approximation yields an NDA receiver. The performance of both receivers in terms of bit error probability is analyzed. We point out the existence of an unmodulated component in the sufficient statistical representation of a COCPFSK signal, and show how this component enters directly in ML carrier recovery. This leads to the interpretation of the NDA receiver as a generalization of the conventional matched-filter envelope-detector receiver. The insights gained here are useful to the problem of ML carrier recovery for Viterbi decoding of CPM signals. © 1990 IEEE