[time-nuts] Phase noise measurement with a scope
Marek Peca
marek at duch.cz
Wed Jun 12 21:36:43 UTC 2013
>> My point was, that DSO is basically an ADC. Therefore, there is some amount
>> of noise, nonlinearity and drift, limiting the jitter measurement. Do you
>> think any method can dig more information from given data than sinc()
>> interpolation and zero-crossing computation?
> The cross-spectrum averaging does indeed do just that, relying on two
> ADCs to produce uncorrelated noise, which can be averaged out.
>
> Or am I misunderstanding your point?
Nothing against that. It depends on what noise level after averaging you
require. I only posted my experience with a very low-quality DSO, which
has 100psRMS single-shot. Using sinc() interpolation, but my point was,
that I suppose there is no way to obtain better single-shot performance
than this. To average out 100psRMS to, say, 1psRMS, it would require 10^4
edges (under the assumption, that the 100psRMS is well behaved noise).
What performance it could yield with a better scope? I hope I'll try
LC584AL some day, I guess it might give sth like 10psRMS single-shot...
Regards,
Marek
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