Synchronization between bits is probably the hardest part; offhand I don't know how to begin looking at that. Within a given bit, given the properties describe

Synchronization between bits is probably the hardest part; offhand I don't know how to begin looking at that. Within a given bit, given the properties described of the waveforms (one notably less than half the frequency of the other) as well as the tolerances involved; maybe something edge or center-crossing focused. Possibly use the peek or zero-crossing as a switch on a charge accumulation counter and measure with a comparison amplifier of any kind.