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by KK7NIL 728 days ago
Not that I'm aware of.

You could generate an eye diagram with an old sampling scope or BERT for probably less than $2k, but those likely wouldn't have the proper clock recovery, which means your horizontal would be sort of pointless. You'd have to make a separate clock recovery module to sit between your USB 3.1 DUT and the instrument.

The other option would be to try and make a real-time ADC with enough BW (at Tek we demoed USB 3.1 debugging with just 10 GHz on an MSO6B, even though compliance testing requires 12 or 15 iirc) and memory depth to do the clock recovery in DSP. This would be a very significant challenge, but might be possible, depending what ADC's are on the market now a days.
1 comments
CamperBob2 728 days ago
The other option would be to try and make a real-time ADC with enough BW (at Tek we demoed USB 3.1 debugging with just 10 GHz on an MSO6B, even though compliance testing requires 12 or 15 iirc) and memory depth to do the clock recovery in DSP. This would be a very significant challenge, but might be possible, depending what ADC's are on the market now a days.

It strikes me that if you ran it long enough, there is probably no reason why a sampling scope couldn't do the same thing. It would need even more DSP eggheadery than the realtime scope, of course.

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KK7NIL 728 days ago
No because modern high speed serial uses clock recovery for the timing (implemented as a first or second order PLL in the receiver), so you need to implement this in your scope too. In a real-time scope this can be done in software but in a sampling scope it has to be done in hardware and then fed into the trigger.

If you just trigger off the edges in the signal all you'll be measuring is the scope jitter.

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CamperBob2 728 days ago
If all you want is an eye diagram, you may not necessarily care about clock recovery, though. You'd just need a high degree of control over your own sampling clock (i.e., better than whatever you're trying to measure.)
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KK7NIL 728 days ago
For amplitude (the vertical part of the eye), yes. For jitter (the horizontal part), which is usually the most critical, especially for NRZ protocols like USB 3.1, no, you need clock recovery.
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