[time-nuts] DMTD mixer question
Bruce Griffiths
bruce.griffiths at xtra.co.nz
Wed Dec 3 20:01:52 UTC 2008
Lux, James P wrote:
>>> Cheers
>>>
>>> Pablo
>>>
>>>
>>>
>> Pablo
>>
>> 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.
>
>
> Jim
>
>
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.
Bruce
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