A digital transmission system using quaternary partial response CPM: principle structure and measurement results

The traditional drawbacks of continuous phase modulation (CPM) a high complexity decoder and difficult synchronization have been overcome by state reduction techniques and a suitable representation of the CPM signal by time-limited base functions. An implementation of quaternary partial response CPM schemes using this approach together with an extended synchronization strategy to combat frequency offsets is reported. Measurement results confirm simulation results, especially the predicted negligible loss due to application of reduced state sequence estimation algorithms. The proposed implementation leads to CPM schemes with complexity and efficiency comparable or even superior to trellis-coded PSK schemes