2 GHz Active Probe
jmw.name
2 GHz Active Probe
1–10 of 30 posts
Re: 2 GHz Active Probe
#2Is there any open source DIY project to relatively cheaply measure the analog performance of USB 3.1 (10Gbit/s) signals?
Re: 2 GHz Active Probe
#3Is there any open source DIY project to relatively cheaply measure the analog performance of USB 3.1 (10Gbit/s) signals?
What does “analog performance” mean in this context? Are you talking about noise, reflections, etc or something else?
Re: 2 GHz Active Probe
#4Is there any open source DIY project to relatively cheaply measure the analog performance of USB 3.1 (10Gbit/s) signals?
What does “analog performance” mean in this context? Are you talking about noise, reflections, etc or something else?
I mean anything that can give more information than just the digital bit errors. Like eye diagrams and such. Basically something that can rate the signal quality on some scale wider than "works? yes/no". Bit error rate is typically too low to give a useful indication.
Re: 2 GHz Active Probe
#5Is there any open source DIY project to relatively cheaply measure the analog performance of USB 3.1 (10Gbit/s) signals?
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.
Re: 2 GHz Active Probe
#6Is there any open source DIY project to relatively cheaply measure the analog performance of USB 3.1 (10Gbit/s) signals?
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.
Re: 2 GHz Active Probe
#7Is there any open source DIY project to relatively cheaply measure the analog performance of USB 3.1 (10Gbit/s) signals?
> 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".
Re: 2 GHz Active Probe
#8Is there any open source DIY project to relatively cheaply measure the analog performance of USB 3.1 (10Gbit/s) signals?
> 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 fundam…
I was thinking of skipping the probe entirely, and just having a USB receptacle on the board, then have a front-end IC that is hopefully available and that is fast enough to do the sampling. Along with some circuitry to make the other end talk USB3.1.
Re: 2 GHz Active Probe
#9In case folks don’t know about the “El Cheapo Special” - you can make very respectable 2GHz passive scope probes with 150ps rise times out of RG-174 coax cable and 1k resistors.
Clip the cable in half, solder the core to the 1k resistor, and the other end of the 1k resistor to the signal you want to probe.
Solder the shield braid to board GND.
50ohm terminate your scope, set probe amplification to 20x, and voila!
Excellent tip recommended both by Paul Horowitz (Art of Electronics) and Howard Johnson (High Speed Digital Design). Works like a charm!
Re: 2 GHz Active Probe
#10Is there any open source DIY project to relatively cheaply measure the analog performance of USB 3.1 (10Gbit/s) signals?
> 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 fundam…
The old rule of thumb that you want the bandwidth to be 3 to 5x your baud rate is no longer true. It has been found that BW as low as 0.7x has very little effect in TDECQ and so the newest optical ethernet standards have moved to that for standards testing and the electrical standards will likely soon follow.
This BW is also applied as a 4th order Bessel-Thompson instead of an oldschool 1st order gaussian response.
Real-time scopes go up to 110 GHz now! Sampling scopes are unfortunately dying out now a days.