[time-nuts] Phase noise measurement with a scope

[Magnus Danielson]

On 06/13/2013 06:00 AM, Chris Albertson wrote:
> My dim memory says there is some analog way to multiply the phase noise.
>   What does that?   Then it might be easier to measure.

Simple, you multiply frequency. The time errors will remain but for a 
shorter cycle, so relative the carrier it has a higher value.

So, a step-up PLL might be what you want for that.

Cheers,
Magnus

>
>
> On Wed, Jun 12, 2013 at 2:36 PM, Marek Peca<marek at duch.cz>  wrote:
>
>> 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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