Marek Peca wrote:
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.
I was thinking about using a 4-channel scope with cross-spectrum averaging. Look at the Timepod by John Miles for an example of the method. I'm trying to guesstimate if the R&S RTO scope, perhaps with the aid of the I/Q option, is capable of doing such measurements, and with what kind of performance.
Cheers Stefan
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