[time-nuts] Phase noise measurement with a scope

Marek Peca marek at duch.cz
Wed Jun 12 17:36:43 EDT 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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