A novel partially coherent detector for joint data detection and carrier phase estimation of continuous-phase-modulated (CPM) signal is presented. The algorithm differs from coherent Viterbi algorithm only in the metric which it maximizes over the possible transmitted data sequences. This metric is influenced both by the correlation of the hypothesized signal with the received one and the current carrier phase estimate. The system has been simulated and comparisons made with existing detection techniques on channels with additive white Gaussian noise and carrier phase jitter. Simulations of the detector are used to assess the relative susceptibility of different CPM (continuous phase modulation) schemes to phase jitter. The trend is that narrower band schemes are more sensitive to carrier phase inaccuracy than the less spectrally efficient ones.>

The power efficiency of coded modulation schemes in additive white Gaussian noise depends on the signal space distribution of their most common error events. Symbol error probability calculation allowing for the pairwise interaction of these error events is discussed. Two optimality criteria are considered for detectors. The first minimizes the probability of symbol error for each symbol decision. This is called the symbol-to-symbol detector. The second (which is superior) is the maximum likelihood sequence detector (MLSD). A lower bound for the symbol-to-symbol detector and an approximation to the MLSD symbol error probability are described. The theoretical performance difference between these two detectors is given. The results are more accurate than minimum squared Euclidean distance predictions, especially at low and intermediate signal-to-noise ratios. The MLSD symbol error probability approximation is obtained for considerably less cost than computer simulation and gives more insight into the signal space structure of the scheme being analyzed. Numerical results are presented for a continuous phase modulation (CPM) example.>