2 GHz Active Probe (opens in new tab)

The catch however is that this can cause (relatively) high resistive loading, so isn't really suitable for all applications.

> Is there any open source DIY project to relatively cheaply measure the analog performance of USB 3.1 (10Gbit/s) signals?

For this kind of thing (measuring eye diagrams and such, as you mentioned in another comment) you'd need a probe-oscilloscope system with (at minimum) 30 GHz at the probe tip. Realistically you'd want 50 GHz, and more is better. Recall that square waves are composed of odd harmonics of the fundamental (~10 GHz), and the more harmonics you capture the more fidelity you'll have to the original.

I don't think there are any real-time scopes with this much bandwidth, so you will need a (equivalent-time) sampling oscilloscope. Keysight might make one, but it probably costs "call us" dollars.

[Edit: Actually, it looks like the SD-32 sampling head for the Tektronix 11800 series of sampling scopes does claim a bandwidth of 50 GHz. That plugin does not have internal triggering though, so you would need to add a trigger recognizer head and arrange for an external trigger signal. Also, don't buy these used on eBay unless the sell offers returns because the sampling diodes in the frontend are very delicate.]

One additional wrinkle is that super-speed USB uses a differential pair with a characteristic impedance of 50 Ohms (each side of the pair is 100 Ohms, and terminated with a 100 Ohm resistor). That means you'll need a differential probe (or two probes and an oscilloscope that can do math).

I don't know of any DIY project with those ambitions, but the most likely route for something DIY is a passive Z0 probe: You want the DUT-probe interface to look like an impedance-matched power divider. That calls for a probe impedance of 10x (or even 100x) the transmission line, so 500 or 5000 Ohms.

Anyway, I don't know of any DIY project that fits your needs, but the terms to search for include "Z0" and "passive".

Given the required front-end bandwidth, ADC bandwidth, and processing power, I don't think so. The closest thing you can do is perhaps get your hands on a FPGA board that has >10G serdes, and use the internal eye monitoring features to check the eye diagram, mask margin, etc.

No, there was a DIY diode prob with a headline number high enough, but I think he said real world performance would be about 8ghz, that's only part of the problem anyway. I had a look, I can't find the forum post or the podcast he was on (amphour). Either rent an appropriate USB analyzer or scope. If you just want to verify the speed of your consumer equipment look for a software solution to measure throughput (there is significant protocol overhead). At the required speed you can't even use BNCs.

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.

What does “analog performance” mean in this context? Are you talking about noise, reflections, etc or something else?

if you want to do this, you generally want a breakout board that breaks out the high speed differential signals to 50 ohm RF connectors and hook that up to a 50 ohm terminated real time scope, and not use a probe.

also for 10gbps per lane, you need at minimum 5ghz bandwidth.