About 22 years ago I decided to get my fly fishing mojo together. Understanding that casting is fundamental to my goal I took a class with a guy donned the “Casting Nazi” by the local Fly fishing club. I got good, practiced casting, dealt with the instructors salty personality, fished, for a couple of years I was a bit unbalanced. Two years later I went on a salt water fly fishing trip for redfish in a guided flats boat in Florida. The wind was howling +20mph, the boat was moving, the fish were moving, the guide was shouting over the wind in frustration trying to help me place the fly with about dinner plate accuracy typically 20-50 feet from my position to traveling visible fish. I felt so defeated. I had a long journey to be a fly fishing “Master”, I wasn’t even close.
Assuming your past the basic issues with making a good measurement, what does it take to be a Master at making VNA measurements from a Signal Integrity Practitioners perspective?
A good fraction of the S-parameters I encounter have serious issues – they are plagued with passivity violations, the VNA wasn’t set up properly, fixturing issues, the calibration was not validated or even checked, loose cables… the list goes on. Around 2002 I proposed a Test/Measurement track in DesignCon, and after a bit of fanfare it was adopted and has turned out to be a valuable track. I co-chair the track with a few other folks, so I see a lot of energy focused on getting a good S-parameter models.
My essential background includes making a lot of measurements to 50GHz, including fast TDR, designing platforms to validate S-parameters, and corresponding them to 3D-EM analysis. My Company has conducted quite a bit of VNA training and we market products for the SI type engineer. I want to share my observations in this blog. Although I consider myself good, I am still no Master, buy I keep trying.
The Beatty Standard
The Beatty Standard is an invaluable tool for calibration validation, material extraction, 3D EM analysis. Ill be discussing this in upcoming blog.
The first consideration is to discuss all the relevant elements of what is required to be the VNA Master, and my list (your list will be different of course) :
Complete understanding of types of calibrations and terminology, for example insertable versus non-insertable calibration, mixed-calibrations, etc., also versed in de-embedding methods in addition to classic
Extrapolating to DC without destroying the S-parameter causality and distorting time-domain convolutional-based simulation
Understand the underpinnings of SOLT, TRL, LRM, SOLR, and perform those calibrations
Understand limitations of VNA including IF bandwidth, number of points, averaging impact on S/N, and associated Source/Load matching, Directivity, and general error models
Design on-board TRL calibration that works to 50GHz
Ability to perform consistent calibrations ( even hybrid and multi-tier), resolve issues with calibration problems, and verify the calibration with external standards
Understand the measurement requirements based on the DUT and reasonable requirements
Ability to interpret single-ended, differential, and modal S-parameters based on a structures topology and layout
Technically not part of the VNA, but correspond S-parameters with TDR and VNA time domain methods. I would add ability to establish time-domain measure-based models as well
Interpret frequency domain of classic structures like stubs, resonators, Beatty Standards, etc.,
Ability to prevent passivity issues and minimize causality problems, correcting minor passivity issues
Able to generate Rational Compact models of S-parameter data, and understand why this is a useful tool
Ability to create multi-port S-parameter matrix from 2 and 4-port analyzer (for 12-port crosstalk aggressed systems for example)
Ability to gauge connectors/adapters and identify bad ones, ability to buy the right VNA cables and create a complete adapter kit
Let’s digress and discuss a more global concept: How long does it take to become an expert in any given area of human activity? Well, a popular book by Malcom Gladwell called "Outliers" he put forth some a basic maxim of mastery; it takes 10,000 hours to become an expert in anything. If this is true then that means you can become good at anything given you put in some serious time. Maybe the time issue is really a reflection of the level of commitment of the individual.
The XTALK-32 is an industry first product. It creates any flavor of crosstalk for 10-56 Gbpsec data.
We incorporated a novel low return loss, high signal integrity crosstalk coupler that provides clean crosstalk energy without attendant return loss or mode issues. Three levels of coupling is included to mimic backplane signal integrity (return loss -20, -10, and -5dB at Nyquist)
XTALK-32 Microstrip Coplanar Coupled structure and it's ADS model equivalent
Results of ADS simulations
If you're interested in learning more about the XTALK-32 Platform you can go to our product web page HERE.
This new platform will in in Booth 752 at DesignCon, along with ISI-32, a loss platform for use with XTALK-32 using WRT skew matched cable pairs.
Easy SERDES Characterization, EDA friendly, Industry First Channel Platforms
January 11, 2016
The ISI-32 and XTALK-32 provide ability to create loss from -3dB at Nyquist to -50dB and RX crosstalk noise from 100uV to 200mV RMS over a wide set of return losses. SERDES testing just got a lot easier with these EDA friendly platforms. See us at Booth #752 at DesignCon next week.
September 23, 2016
Eric Bogatin, founder of the Signal Integrity Academy at BeTheSignal.com, announced the publication of a new signal integrity eJournal and web site called Signal Integrity Journal.
Eric posted the following information to the SI-LIST news lister group:
I thought you all might like to know about a new SI resource just starting up. Horizon House publishing has just announced the Signal Integrity Journal. You can see the press release here:
The Journal will start as a web site and grow to a digital publication soon. I was invited to be the editor, with a distinguished group of editorial advisory board members, including many SI-list icons, Istvan Novak, Al Neves, Beret Simonovich, Doug Smith and Yuriy Shlepnev.
The goal of the web site and journal is to provide high value content on signal integrity, power integrity and electromagnetic compatibility and integrity topics ranging from best design practices, measurement and simulation tools, materials, components and technology options and application case studies. What did I miss that is important for designers to get to an acceptable product design faster?
You can check out the initial pages of the web site here: https://www.signalintegrityjournal.com/ Be sure to click on the green box
to subscribe to the newsletter and get the updates on new content posts and the digital magazine.
If you missed it, here is the link: https://www.signalintegrityjournal.com/user/new
As with the sister publication, Microwave Journal, all the content on the SI Journal site and the coming digital magazine is completely free.
In addition to my beTheSignal blog posts, I am writing a new column, ".it depends, reflections from Eric Bogatin" Check out the first post!
We welcome original contributions from all engineers. Here is the link to the submission guidelines: https://www.signalintegrityjournal.com/submissions. If you are "shy" and I see you presenting something cool, I will probably hit you up to write something up for the SI Journal.
Please send your ideas, outlines, or final drafts to Pat Hindle.
Hope you enjoy this new resource for our community.
--eric, Editor, SI Journal.