Towards a Low Complexity Implementation of a Multi-H CPM Demodulator

Abstract

Multi-h Continuous Phase Modulation (CPM) is a promising waveform for aeronautical telemetry because it is a compact spectrally efficient constant amplitude modulation. It has been selected as the Advanced Range Telemetry (ARTM) tier II waveform owing to these qualities. However, it is also a complicated waveform that has the reputation of suffering from complex demodulation processing and high sensitivity to transmission impairments and in particular synchronization aspects. In this paper we review a set of complexity reduction techniques that intend to bring this waveform into the domain of operational telemetry waveform, by allowing low complexity hardware implementation without sacrificing performance or robustness. Most techniques are adjustments of recent literature results, concerning both demodulation and synchronization. Computer simulation of a receiver implementing theses techniques shows negligible performance loss compared to optimal coherent demodulation with perfect synchronization. Hardware implementation confirms that nearly optimal performance can be achieved with hardware resource currently available in middle range FPGAs.