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Have not  used BERT

Author

Thanks everyone. Great questions. Keep 'em coming tomorrow.

Author

Thank you very much. Good information today.

 

Author

Thanks for your response.  I guess I'll have to measure jitter multiple ways and see if the measurements converge......

Author

Now I'm really shutting down and going for a cup of tea.

Checked back before actually leaving...

I think you can believe them as much as you believe anything--that is, find out what they're actually doing and then decide for yourself if it makes sense. Compare results across platforms and if the numbers come within 10%, consider them consistent.

You mentioned that the BERT is the standard for the measurement of TJ.  The BERT from company "A" also gives a measurement RJ and DJ and company "T" also has a deeper decomposition of the jitter components.  Can I believe these numbers or only trust the TJ measurement?

Author

Thanks for today's lecture Ransom

Author

Okay, if you're still here... I'm leaving now.

See you tomorrow! I hope you're having fun.

Givanov,

You don't want to get me started on test patterns. Emerging specs require PRBS31, which is a stupid choice because it's so long that no equipment (not even BERTs) can measure TJ with appreciable statistical significance on that pattern.

Check the DesignCon site for a paper last year by Marty Miller on test pattern lengths.

I wrote one for Tek, but the link seems to have gone away. Send me a note and I'll get it to you: ransom@ransomsnotes.com

Check websites of the usual suspects for white papers that slice and dice the alphabet soup of DJ categories. Searching "jitter analysis" will get you rolling.

 

References:

This old paper I wrote when I worked for Agilent is pretty formal, quite complete, just ignore the marketing garble at the end, that parts outdated:

http://cp.literature.agilent.com/litweb/pdf/5989-3206EN.pdf

It's also one of the most oft cited references on the subject.

Thanks Ransom for another great presentation. I was wondering if you have compiled or know of some interesting article that covers the different jitter signatures (PDF terms or other) including compound effects of more than one noise source?

 

Author

The other thing to remember is that *there does not exist* equipment that can measure TJ(BER) with accuracy better than 10% or so. Equipment may be repeatable to a few percent, but it's not any more than 10% closer to the "true" value so don't work late trying to get below 10%, you can't.

What qualifies a suitable test pattern for BER testing? Worst case one - that stimulates all the negative effects or a "real world" one that considers the statistical occurance of the negative contributors?

Author

if you want to go back and listen to some of the audio, the archived audio is now available above. I know I need to run through it again!

Author

A couple more things:

The specs to look for on BERTs for jitter analysis are error detector sensitivity, you want it as low as possible, I think 10 mV is state of the art. And linear time base, of course.

Ok, thanks for the reply.

Author

Strieu,

Always Rasta, my man. Always Rasta.

The question in volves differences in left and right sigma affecting the TJ result.

The answer: it can get ugly. For electrical systems, when they differ widely, look deeper, something is probably wrong with the transmitter or you need to fit farther and farther down the tails.

For optical systems it's more complicated and you see left-right asymmetries more often.

My prejudice, especially since I don't have to pay for test equipment, is to do the full measurement with a BERT and see what's really going on. If there really are asymmetries, you'll have check the accuracy of your dual-Dirac estimate with the BERT measurement.

Zam!

Performing the full measurement on a BERT is more accurate, if only because you're not making the leap-of-faith that is extrapolation.

Givanov's question:

>> How does acuisiton noise influence the BER/TJ measurements - is tere an established way to calculate those effects out?


Acquisition noise is always tricky. In my experience it's worse on real-time scopes than equiv-time scopes and BERTs. To subtract it out you have to make assumptions about how it's distributed. If you assume the noise is Gaussian you can come up with techniques to remove it, though it's never clear how that affects your systematic uncertainty.

Have a great day. Well presented and well defined

Theo

Author

Which meathod is more accurate, the BER or dual-Dirac model for measuring total jitter?

Author

Thank you very much for a nice presentation.

Author

I didn't hear back from Ransom about the reasoning behind his statement that FeXT was more important than NeXT.  It is commonly accepted that FeXT is less important than NeXT, especially for embedded striplines.

 

Author

Thanks for your great presentation. I prefer Rastaplot and will be using that terminology from now on. ;) Slide 23: Is there a case where sigma R and sigma L are so different that averaging them would cause major inaccuracies in the model?

Author

Hi Hemanshu,

I'll dig up a couple of references for you in a few minutes. Or if you want to san through my web page www.ransomsnotes.com there's a lit of white papers if scroll down that includes dual Dirac references

Thank you, all contrubutors!

Author

Thanks Ransom....great lecture!!

Author

Thanks, Ransom and Janine.

Author

Thanks, first time seeing this

Author

How does acuisiton noise influence the BER/TJ measurements - is tere an established way to calculate those effects out

Author

Thanks Ransom and Janine.

Author

Very nice analysis of the measurement methods.

Author

Thank you Ransom & Janine for the great lecture.

Author

Regarding dual-Dirac model, it was not very clear to me. can you please refer to me some application note on the topic that you think is relevant.

Thanks for the presentation.

Yes have used BERT; Thank You Ransom & Janine

Author

Thanks. First time I learn this.

Author

Thanks for the lecture.

Author

Bathtub on the logarithmic scale as well.

Author

Yes, multiple - modular parallel BERTs, serial boxes, etc.

From sunny & soon-to-be-hot Oregon.

Hello everyone! from Bremen, Gr

 

Author

BERT used extremelly ofter here for newtork health check

Author

Have you ever used a bit error rate tester?

Author

Good afternoon, everyone.

Author

And, here we go day 3!!  Audio is up and sounds great.

Author

Good morning from Santa Clara.

Author

Hi ALL, Good Afternoon from HOT,HOT,HOT BOSTON!

Author

Hello fron sunny Atlanta

Author

Hello from Ottawa, Canada

Author

Good morning

Sergio López

Author

amidst dirac delta thunderstorms here :)

Author

goodmorning! from San Diego

Greatings from Toronto

Theo

Author

Good Morning from Panama City, FL.

Author

Hello from Huntsville, Al

Author

Its Fall in Florida. 85 and cool north breeze.

Author

Hi everyone. If you are new to the course...The streaming audio player will appear on this web page when the show starts at 12:00 pm  Eastern today. Note however that some companies block live audio streams. If when the show starts you don't hear any audio, try refreshing your browser.

Author

It's hot and steamy here in NJ as well!

Author

Good Morning from hot and steamy Boston!

Author

Good morning! Be sure to click 'Today's Slide Deck' under Special Educational Materials above right to download the PowerPoint for today's session.

Author


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