[time-nuts] DMTD mixer question

[Bruce Griffiths]

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