Pulse code demodulator for frequency shift keyed data

摘要

A demodulator which directly decodes Pulse Code Modulated Signals initially modulated by Frequency Shift Keyed Data by determining the period between zero crossings. The instant of the zero crossing between PCM signal samples is determined by interpolation from the magnitude of the samples immediately preceding and succeeding the zero crossing upon detection of a change in the sign bit of the PCM signal.