Re-Engineering PCM/FM as a Phase Modulation Scheme

Abstract

Historically, (PCM/FM) receivers have used simple detection schemes yielding low performance. Using multi-symbol detection methods, PCM/FM can be received with better error performance than either SOQPSK or multi-h CPM. We present an approximation by which PCM/FM can be reinterpreted as a phase modulation scheme, allowing the use of coherent detection techniques. This is backward compatible with existing receivers. We also present an extension by which the error performance of the approximated PCM/FM can be improved even further with no change to the spectral properties. This improved waveform can be used in systems where compatibility with existing frequency allocation schemes is required.