Keywords

aeronautical telemetry, CPM, digital communication, multi-h CPM, PAM representation

Abstract

ARTM CPM is a partial response, two-index continuous-phase modulation that was adopted as a standard in IRIG 106-04 for aeronautical telemetry. This waveform was selected because it achieves approximately three times the spectral efficiency of PCM/FM. However, the optimum receiver requires 128 real-valued matched filters and keeps track of the waveform state with a trellis of 512 states and 2048 branches. Various complexity reducing techniques are applied and the resulting loss in detection efficiency is quantified. It is shown that the full 512-state trellis is not required to achieve the desired detection efficiency: two different 32-state configurations were found to perform within 0.05 dB of optimal; two different 16-state configurations were found to perform within 1.0 dB of optimal; and an 8-state configuration was found to perform within 1.05 dB of optimal. The analysis and simulation results show that to achieve a given state complexity, proper combination of two or more complexity-reducing techniques generally outperforms the use of a single complexity-reducing technique.