[time-nuts] Phase noise measurement with a scope

Marek Peca marek at duch.cz
Wed Jun 12 13:32:42 UTC 2013


Hello,

> given that digital scopes have a multichannel ADC for acquisition, which is 
> similar to what a cross-correlating phase noise measurement instrument has, 
> it occurred to me that phase noise measurement might also be possible with a 
> standard digital scope and some post-processing software. The scope usually 
> will have only 8 bits of resolution, but it will have a rather high sampling 
> rate. With oversampling math, one may be able to trade one for the other, at 
> least if the scope's analog frontend is not too bad.
>
> Has anyone investigated or tried this? Is it a silly idea to start with?

yes, did it last week. I think it may have a sense with >1Gsps scope with 
good quality guts (should check with LC584AL at work).

I have tried it with a very cheap one, Rigol 2-channel, originally 50MHz, 
reflashed to 100MHz. 2 signals, ref&measured, into Ch1, Ch2. Waveforms 
(2x500Msps) acquired, sinc() interpolated. Results: short-term single-shot 
jitter around 100ps RMS. Long-term was of no interest for my purpose now, 
so no observations here.

Therefore, it is almost of no use at all for higher precision needs.


Regards,
Marek



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