Signal Integrity: Back to Basics

Entries from May 2009

Signal Integrity Textbooks

May 28, 2009 · Leave a Comment

(Syndicated content from: http://signal-integrity-tips.com/2009/signal-integrity-textbooks/)

Here are my thumbnail reviews of some signal integrity textbooks. They reflect my personal views, not those of Agilent. You can add your thoughts in the box below.

  • Timing Analysis and Simulation for Signal Integrity Engineers by Greg Edlund
    This book takes a different approach to signal integrity then the “traditional” Bogatin and Johnson & Graham approach (see below) in that the starting point is not the interconnect, but the prima dona of signal integrity, the flip-flop in the receiving chip. “If I don’t see a clean zero or one during my set up and hold periods,” lectures the flip-flop, one hand on hip, the other wagging a threatening finger, “I’m going to go metastable.” And so the game begins. How to deliver on that demand? Greg’s twenty years – and counting – experience as a hands-on signal integrity engineer makes his textbook authoritative and his narrative style makes the book accessible.
  • A Signal Integrity Engineer’s Companion Real-Time Test and Measurement and Design Simulation (Geoff Lawday, David Ireland, and Greg Edlund)
    Some of the chapters (2, 4, 9) in this books are the same (give or take a revision or two) as ones in the book above, so this book should be considered if the non-overlapping material is of value to you. Not sure why the publisher “double-dips” in this way.
  • Signal Integrity – Simplified (2ed due for release July 27, 2009) by Eric Bogatin
    It was Eric who coined the phrases “There are two kinds of engineers — those who have signal integrity problems, and those who will.” and (with respect to all signal integrity issues) “It depends.”
    I haven’t seen the second edition yet, but the first edition has the “traditional” signal integrity focus on the properties of the interconnect, the impairments that it inflicts on the poor signal, and how to design around them within the limits imposed by physical laws. Eric also has a new book coming out in September, “Signal Integrity Characterization Techniques”, co-authored with my colleague Mike Resso. I’ll review it when I can.
  • High Speed Digital Design: A Handbook of Black Magic and High Speed Signal Propagation: Advanced Black Magic by Howard Johnson and Martin Graham
    Published in 1993 and 2003 respectively, one frustration with these two very popular books is that I can never quite decided whether the latter is volume two of the former, or whether it’s the second edition. There’s certainly a lot of overlap between the two, but the second isn’t a true superset of the first. It smacks of another case of Prentice Hall “double-dipping.” Both volumes/editions have a “traditional” focus on the PRBS signal in the frequency- and time-domains, and its interaction with the interconnect. Personally, I prefer the flow of Eric’s book for “cover-to-cover” reading, but there’s a lot of good reference material and anecdotes here that I dip into when needed.

Other texts that are on my ever expanding to do list. I’ll try to add reviews here someday? Or p>

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Signal Integrity Papers from Agilent ADS User Group Meetings in Rome and B?ngen

May 20, 2009 · Leave a Comment

(Syndicated content from: http://ping.fm/0Mgo7)

The Agilent ADS User Group Meetings in Rome (13 May) and Böblingen (14-15 May) had three signal integrity papers that the authors have kindly given permission to post here.

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Using Equivalent Circuits for the Analysis of Complex Power and Signal Integrity Problems

May 19, 2009 · Leave a Comment

(Syndicated content from: http://ping.fm/jBTWo)
Guest post from Francesco de Paulis and Antonio Orlandi, UAq EMC Laboratory, University of L’Aquila, Italy

At our ADS User Group meeting in Rome May 13th, Francesco de Paulis and Antonio Orlandi, UAq EMC Laboratory, University of L’Aquila, Italy presented a paper Using Equivalent Circuits for the Analysis of Complex Power and Signal Integrity Problems
Using Equivalent Circuits for the Analysis of Complex Power and Signal Integrity Problems
.

They kindly gave me permission to post the slides here

They compare fast circuit simulation with ADS to complex and time consuming 3D models and conclude that ADS is not only a tool for designing. Its flexibility allows its use as tool to investigate the fundamental mechanisms of relevant power and signal integrity issues and that it is a critical tool for engineering

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The Trouble With IFFT

May 15, 2009 · Leave a Comment

(Syndicated content from: http://signal-integrity-tips.com/2009/the-trouble-with-ifft/)
Consider the following MATLAB code which models a lossless delay by its amplitude and phase frequency response, then applies a simple inverse discrete Fourier transform, then plots one period of the time domain response:


close all
clear all
npts = 256;
delta_t = 1e-9; % s
t = 0:delta_t:delta_t*(npts-1);
f = linspace(-(npts-1)/(2*npts*delta_t),1/(2*delta_t),npts); % Hz
amplitude = ones(size(f));
delay = 10.5e-9; %s
phase = -2 * pi * f * delay;
fresp = amplitude .* exp(j * phase);
tresp = ifft(ifftshift(fresp));
plot(t,tresp)

The resulting plot shows that this method cannot be used to create an accurate impulse response:

one period of the time domain response

The pulse is spread out so badly that the skirt of the next period leaks into the end of this one.

The fundamental issues is that to get an impulse response, you have to do an inverse Laplace transform, not an inverse Fourier transform. (The output of an inverse Fourier transform isn’t an impulse response at all: it’s one period of the repeated pulse train response.) “But,” you say, “I don’t have the frequency response in the complex plane, I only have the steady state response on the upper half of the f = j ω line.” Kramers-Kronig relation to the rescue! This relation says that if you have a real physical system i.e. a causal system the frequency response it is possible to construct the impulse response (causal of course) from the steady state data alone.

If you don’t want to do the math (and I don’t blame you for that), don’t worry we’ve done it for you in ADS (US patent pending, application 20080281893).

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Fifteenth Anniversary of the SI-List

May 15, 2009 · Leave a Comment

(Syndicated content from: http://ping.fm/LnblX)

The si-list went “on the air” fifteen years ago today, on May 15, 1994 — an eon in Internet-years. It predates that milestone moment of the Internet: the IPO of Netscape on August 9, 1995.

The genesis was a short course on "Electrical Modeling, Simulation and Design of Electronic Packages" that was taught by Raj Mittra, Paul Franzon and Jose Schutt-Aine in San Jose, CA on May 9-12, 1994. During the last day of class we passed around a blank piece of paper collecting e-mail addresses from anyone who wanted to be included in a proposed signal integrity email list. When I returned to my office at Sun Microsystems the following Monday I put together the initial si-list with about 30 subscribers from the previous week’s short course.

Now 15 years later we have about 3,500 subscribers. They range from students just getting their feet wet in engineering to world-renowned experts in the field. They hail from both industry and academia in just about every country in the world that is involved in signal integrity related endeavors.

The original idea was to provide a forum for the exchange of technical conversation related to signal integrity and related fields. Over the years we have endeavored to keep the majority of the list traffic on the technical level and to control the use of the forum for advertising and head-hunting. To that end I think we have been remarkably successful. Let me take this opportunity to remind folk that working engineers and hiring managers looking to add to their staff may post job opening and that postings by ‘headhunters’ and HR departments are generally discouraged. Postings by vendors (hardware and software) should be primarily technical in nature and should not be mere advertisements. Si-list is not a marketing forum. Vendor postings about commercial products should refer those interested in further information to an e-mail, web address, or phone number for more detailed follow-up.

A bit of behind the scenes history:

  • The original si-list incarnation was implemented as a simple Unix .forward file on an ancient Sparc2 workstation in my office. All list administration (additions, deletions etc.) was done manually.
  • As the list grew,  we transitioned to the Majordomo listserver software and ran the list from a slightly less ancient Sparc4 box located in our SI lab.
  • Over the years the subscriber database and the attendant bandwidth on the net increased. In order to head-off a cease and desist order from the keeper of the Sun LAN, si-list was moved to an external Linux server (freelists.org) running the Ecartis maillist manager software in June 2001. The list still resides on that server today. Thanks to the Freelists admins for years of fine service!

If you want to look back at the postings, archives are available at these locations:

Thanks to all contributors over the past fifteen years.

Happy fifteenth anniversary si-list!

Ed: Related post What Social Media Web Sites Do Signal Integrity Engineers Use?

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