Published by Eric Bogatin on 18 Nov 2009
In preparing for a paper at DesignCon 2010, I’ve been reviewing books and papers related to frequency dependent material properties and their effect on signal quality, especially at high data rates.
I’ve come across two excellent books that cover this topic, as well as many other advanced SI topics, better than any others I’ve encountered. They are Advanced Signal Integrity for High-Speed Digital Designs by Stephen Hall and Howard Heck and The Foundations of Signal Integrity by Paul Huray.
If you want to understand what characteristic impedance is, or why SSN is created by gaps in the return path of a signal, read my book, Signal and Power Integrity Simplified. But, if you want to trace the origins of signal integrity effects back to Maxwell’s Equations, read these books.
Advanced Signal Integrity for High-Speed Digital Designs by Stephen Hall and Howard Heck, is a bit of a sequel to Stephan Hall’s previous book, High-Speed Digital System Design. If you have this book, it is well worth upgrading to version 2.0.
Hall and Heck cover the traditional SI topics of E&M fields in transmission lines, reflections, cross talk and differential signaling. There is no coverage of PDN issues, but the sections on resistive loss, dielectric loss and equalization techniques easily make up for this.
In all of my searching, I found no better explanation of the Kramers-Kronig relation and how it drives the causal relationship between the resistance and inductance per length of a transmission line, or causal material properties. They describe the impact from RMS roughness on series resistance, even introducing the Huray model for copper surface texture.
The most useful section for me was on the models for the real and imaginary parts of the complex dielectric constant and the origins of the single, multiple and infinite pole Debye models. While this topic has been covered many other places, this chapter takes you from start to finish, giving you the tools to immediately apply this model to board design.
If you want to go the next step beyond Hall and Heck and re-calibrate your intuition about how to apply Maxwell’s Equations to Signal Integrity, you need to get Paul Huray’s new book, The Foundations of Signal Integrity.
In the interests of full disclosure, I freely admit that I have recently had the distinct honor and privilege of working with Prof Paul Huray on a project with a few Intel Engineers and have been able to “learn directly from the master.”
While another mentor of mine, Yuriy Schlepnev, the president of Simberian Software and architect of the 3D full wave simulator, Simbeor, has tried to teach me the right way to apply Maxwell’s Equations to signal integrity, I never spent enough time with him for his teachings to sink in.
From Prof Huray, I have finally learned what Yuriy has been trying to tell me: “everything I know about the world is wrong.” It’s the fields that do everything and currents don’t really travel down a signal path. Carrying this concept of currents around, while a useful crutch, screws up our intuition about how RMS roughness really affects the series resistance of a transmission line.
Using his expertise in Maxwell’s Equations, Prof Huray has developed an analytical model for how signals are affected by the surface texture of copper which matches actual behavior well above 30 GHz. You will hear more about his approach at DesignCon 2010.
Prof Huray has condensed his years of teaching graduate level EM classes and his research programs which apply EM first principles to signal integrity problems into his latest book. This is not for the faint of heart. But, if you want to learn the right way of thinking about Maxwell’s Equations this is the book for you.
Since it’s the fields that really do all the work, he has color coded all reference to E fields in red and all reference to H fields in blue. The dramatic illustrations of the relationships between propagating E and H fields in waveguides, at boundaries and in various materials are tremendously valuable and also follow the color codes. This makes it much easier to follow the path from Maxwell’s Equations to their application in signal propagation.
Almost half of the book covers the very important topic of the role of material properties on signal propagation. As might be expected, he introduces the Huray model for copper surface texture and how this model can be extended to more irregular copper textures.
The serious engineer can find no better pair of books than these. Through their guidance you will be able to trace your way back to how, with Maxwell’s Equations and the right boundary conditions and material properties, all of signal integrity naturally flows. Their value will only increase with time as digital electronics encroaches more and more into the microwave world.
For information on this and other multi gigabit topics, check out our new class, Multi Giga Bit Design (MGBD).