"Cheapest" Equipment for measuring + optimizing 2.5 Gbps LVDS

[luky315]

I have a quite long LVDS chain with equalizers and isolators (ADN4622). Unfortunately there are sporadic bit errors and I need to look at the signal at different stages to optimize the equalizer settings and etc.
What would be the most cost efficient solution for this problem? Maybee a SJL GigaWave sampling scope and a frequency generator (EraSynth?)
I have a budget of 3000€, including probes.
And a related question: Are there any reasonably priced BERTs (Bit Error Rate Tester) out there? I don't need a lot of extra functions, "just" a device that transmitts data, receives it and then calculates the error rate.

[tszaboo]

I would start with an Eye diagram at different stages. So a sampling oscilloscope, and DIY Z0 probe (or a pair of good probes that come with it) is probably the cheapest way to evaluate that.

[luky315]

Which "low cost" sampling scope is able to take Eye Diagram measurements? I know that the measurement is not that simple (or better it is not that simple to get reliabble measurements, its simple to make something that looks like an exe diagram) with realtime scopes.

[tszaboo]

Which "low cost" sampling scope is able to take Eye Diagram measurements? I know that the measurement is not that simple (or better it is not that simple to get reliabble measurements, its simple to make something that looks like an exe diagram) with realtime scopes.

Mostly used ones. For this budget, I would look for the rental market.

[uer166]

Which "low cost" sampling scope is able to take Eye Diagram measurements? I know that the measurement is not that simple (or better it is not that simple to get reliabble measurements, its simple to make something that looks like an exe diagram) with realtime scopes.

There's some new-age USB sampling scopes that aren't actually thAt expensive brand new, e.g. this might be (barely) enough bandwidth: https://www.sjl-instruments.com/

edit: just noticed you were aware of these. I think that's not a bad option but have not used one of these myself (just seen reviews).

[luky315]

I have also never seen the "cheap" sampling scopes for taking eye diagrams, has someone experience wirh those?

[voltsandjolts]

Cross-ref:
https://www.eevblog.com/forum/testgear/pocket-sized-6-ghz-1-tss-et-scope/
(maybe someone there has feedback, I didn't read whole thread)

[luky315]

Thanks, the GigaWave looks like a nice device, I'm ordering one as soon as they are up and running again!

[joeqsmith]

I have also never seen the "cheap" sampling scopes for taking eye diagrams, has someone experience wirh those?

If there is something specific you would like me to show with the 6400, feel free to ask. 

Their latest software is pretty decent.  You can download it and run it without the scope in demo mode if you just wanted to try it out. 

[luky315]

Hello Joeqsmith,
I (and I think a lot of other people here...) would be very much interested in your experience with the GigaWave devices. I am a bit concerned that the inputs are only +-1V, so nearly every signal that I have in my line of work  (CML, LVDS, (P)ECL)....) has to be attenuated to look at it

[joeqsmith]

I would think the signals would be attenuated by your choice of probes.  If you needed to look at the trigger's edge, you have a 6dB loss from the splitter as well.  You could check out Lasmux's thread on their active probe as well.  I did show a few decent 10x resistive probes I made. 

There are also two reviews.  The Gigawave thread contains a lot of information that goes beyond the review.  The problem with the reviews is the software wasn't mature while I was working on it.  Some of the problems I ran into were improved after the release.   It made for a choppy video where I repeated a few experiments. 

Have a look and let me know if there is something specific you would like to see.

[luky315]

I have one very basic question: Is the Gigawave the right tool for looking into high speed digital signals? I'm not only thinking about LVDS, but also USB 3.x, Gigabit Ethernet etc. I have often situations where I need to tune transmission lines, very long or non-ideal cables and linear redrivers and each time I have to go back to the HF lab at my old university to use the nice, but absolutely non portable and expensive 40GSPS LeCroy WaveRunner.

[joeqsmith]

Hardly a basic question.  "Right tool" is difficult to answer without you providing all of the constraints.   It's certainly well made, low cost, easy to use, fits in your shirt pocket, open interface allowing you to write custom software for it.  In the case of the prototype they provided, it exceeded every specification they claimed, which I demonstrated as part of my review.

It is a sampling scope which imposes certain limitations compared with your LeCroy.   The next limitation is the trigger.   Then comes the slow update rate (which is going to be signal dependent).  I would say last, you have a product that works differently than a typical oscilloscope.  The company has made a LOT of improvements to the manual which documents much of these details in terms that even I can understand.   I strongly suggest you take time reading that before making a choice.  You could also ask the company for help on deciding if it would be a good fit.  They are very honest and are not trying to sell products to people that can't utilize them.   

As for Ethernet,  I tried experimenting with PAM and I would say for PAM4, it could be useful.  PAM8, things fall apart.  Those experiments are posted in the long thread. 
 
Not sure what you are looking to spend.   Regards to "cheapest", the Gigawave takes it.  But it also needs to fit your requirements or that money is wasted.  That's your job to figure out as no one is going to understand your applications like you.   I mentioned PicoScope a few times in that thread as they also offer a low cost, high BW sampling scope.  Keeping in mind, low cost is 10+. 

Not very helpful but again, if there is something specific you would like to see, let me know.