On Coherent Detection of PCM/FM in Aeronautical Mobile Telemetry

PCM/FM is a continuous phase modulation (CPM) used in aeronautical mobile telemetry. The introduction of modern transmitters capable of producing CPM with an exact modulation has made fully coherent maximum likelihood detection of PCM/FM of interest. This paper describes PCM/FM in terms of its CPM parameters and describes the maximum likelihood detector. Practical issues, such as complexity-reducing techniques in the form of tilted phase and pulse truncation, trellis termination, and sample rate are examined. Computer simulation results show that tilted phase has no impact on bit error rate performance, and that pulse truncation, improper trellis termination, and operation at 2 samples/bit each degrade the bit error rate performance by a small fraction of a dB.