[time-nuts] DMTD mixer question
bruce.griffiths at xtra.co.nz
Wed Dec 3 20:01:52 UTC 2008
Lux, James P wrote:
>> Flipflop mixers tend to produce glitches at the beat
>> frequency transitions.
>> A digital PFD in a PLL doesnt produce a beat frequency output
>> when locked so such glitches arent a problem,
> I don't know that this is the case with modern PLL PFDs.. If only because glitches at the transitions would cause other problems, so there's an incentive to get rid of them.
Surely metastability may occur when the mixer flipflop D input
transitions occur close to its active clock transitions?
There is at least one patent (US5053651) that claims to eliminate such
glitches in a digital mixer, however its output beat frequency is half
the difference between the input frequencies.
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