Phase tracking and demodulation with delay

Algorithms are described for estimating carrier phase by a maximum-likelihood procedure similar to the Viterbi algorithm for decoding a digital sequence. These algorithms avoid the constraint of physical realizability imposed by a phase-locked loop and allow a processing lag in estimation. An approximate analysis suggests that threshold extension can be achieved thereby. Computer simulations demonstrate the improved performance for demodulation of FM and for tracking of phase modulation due to dynamic maneuvers.