A data-directed frequency-and-phase lock loop for an offset-QAM modulated signal
comprises a first multiplier that multiplies the signal by the output of a VCO.
The output of the first multiplier is phase-shifted by a second multiplier, then
convolved by a third multiplier. The output of the third multiplier is split, with
each portion being passed through a frequency-shift multiplier and a frequency-and-phase
lock loop. The output of the two frequency-and-phase lock loops is summed and returned
to the VCO to complete the feedback loop.