Book Review

Title: Platform Interferences in Wireless Systems
Authors: K. Slattery, H. Skinner
Publisher: Elsevier, January 2008
ISBN: 978-0-7506-8757-7

With the advent of mobile computing, wireless communication has become an integral part of the computer platform. Who would now consider buying a laptop without wireless? At the same time, the once simple communications device such as a cell phone now has functions that require subsystems associated with computer devices. The problem is that these devices were never intended to coexist. Communications devices were not designed with high-speed digital logic in mind and high-speed digital logic never included communications as a design vector.

This book has two main intentions, and in my opinion, perfectly achieved: to provide education about the principles of radio frequency interferences (RFI) and to provide a reference source for identifying noise-related issues and mitigating them in actual design scenarios.
One of the key points of this book is that it has been written with the practicing EMI engineer in mind. To that end are provided only the aspects of theory that are necessary and that help the readers to develop their own intuitions and perspectives. Where necessary, the provided equations are converted into code and proposed to the readers for modeling and building their own analysis.
Another characteristic of this book that I really liked is the large quantity of measurement results. They are used as conceptual tools to guide the reader towards the technical conclusions or show how the solutions proposed have an impact on the overall system. This is one of the points of force of this book. At the same time, the black and white edition does not help the full readability of the graphs.
The book is composed of nine chapters and a few appendices (referring to specific chapters) totalling about 333 pages. In the Appendices are illustrated and well commented scripts for Mathematica (Wolfram Research) used to work out the calculations shown in the book. All chapters contain several examples to illustrate the concepts, some of which can be reproduced using the above-mentioned software. These examples can also be used to evaluate the accuracy and speed of several commercial tools that are available today.
Chapter 1, “Introduction,” sets the scene for engineers and students who are entering the field of wireless versus EMI. Here is introduced the concept of wireless interference potentials that nonintentional radiators, in the form of high-speed digital components and signals, have on impacting wireless systems. Also presented is the concept of a platform RF budget and a methodology to assess the RFI risk, taking into account, in a quantitative way, all the pertinent system factors (from radio sensitivity, to noise figures). A well-documented number of measured results show the importance of the study and analysis of platform-generated RF noise for the correct functioning of wireless systems.
Signals are the focus of Chapter 2, “The Structure of Signals,” which covers the many different aspects of the structure of signals and how each element of this complex structure can be addressed to develop a strategy toward minimizing the interference impact of the signals used in the wireless platform. This chapter offers an anatomy of the signal in which every part (edge rate, symmetry, duty cycle, repetition rate, etc.) is physically and mathematically related to its impact on the variation of amplitude and harmonic components. Here also is examined the properties of repetitive and non-repetitive signals, scrambled clocks and clocks spread out in time. The various symbols that are used to construct a video digital display are also investigated.
Chapter 3, “Analysis of Symbol,” is an expansion, in depth, of Chapter 2. After a clear and sophisticated comparison between the platform signals or symbols, there is a discussion of those aspects of the signal structure that may be ignored or that should not exist for RFI improvement. Section 3.3. “Wireless Performance in the Presence of Radiated Emissions from Digital Display-Symbols” deals with the many possible approaches to interference mitigation that may be pursued through application of signal structure modification techniques.
Chapter 4, “Measurement Methods,” as the authors say “a measurement is worth a thousand opinions”, this is the guiding line of this chapter in which are described some of the measurement methods that can be employed in developing an understanding of the EMI problem and in developing the proper mitigation methods. The use of broadband measurements in conjunction with a method to localize and identify emission sources gives the practicing engineer a nearly complete means for identifying and characterizing the interference potential of a given platform. Neither of the proposed methods requires the existence of expensive dedicated chambers. A nice cost budget is offered at the very end of the chapter.
A brief summary of the relevant electromagnetic laws and principles is offered in Chapter 5, “Electromagnetics.” It is the logical premise of the following chapters.
Chapter 6, “Analytical Models,” offers the basis to start building analytical models of the main platform interference sources. The proposed approach assumes that one could take complex structures, such as the interconnect channel, and model them as sets of discrete point radiators. The same strategy is used to model the circuit sources inside the silicon. The chapter focuses on offering a means to compare different source configurations as the engineer develops the functional floor plans in the design stage. At the end of this chapter the reader has a method to quantify potential emission problems and investigate the mitigation solutions.
The aim of Chapter 7, “Connectors, Cables and Power Planes,” is not an academic discussion toward power delivery network design. The goal is a systematic approach for the identification (substantiated by theory, numerical simulations and measurements) of the design features to tune in order to impact the interferences. This strategy is offered in a top-down approach, from connectors, to PCB, to package up to silicon. In this way, all the design features are presented to the designer, each one with its degree of impact on the noise to be mitigated.
In Chapter 8, “Passive Mitigation Techniques,” a selection of the shielding approaches is proposed suitable for the kind of structures dealt with in this book. Each approach can be used in combination with the others to improve isolation between noisy platform components and victim radios. The relative merits as well as the potential pitfalls of near- and far-field applications are discussed in detail. Passive mitigation is a strategy that assumes that we have a noise source and a sensitive victim receiver and attempts to maximize the isolation between them. This consideration opens the way to the next and last chapter in which active mitigation is introduced.
Chapter 9, “Active Mitigation,” deals with the source of the noise itself. In this Chapter, three fundamental topics are illustrated: the frequency planning, the frequency content and the radio improvement. In the frequency planning content, it is discussed how to move the noise out of the radio bands and into frequencies where no radio operates. In the frequency content, the fundamental aspects of digital circuitry are addressed that impact the harmonic content of the noise and, from that, how to derive possible mitigations. The radio improvement gives some direction for possible radio improvements in dealing with noise.
This book’s system-level focus and practical examples make it very useful for all students and professionals concerned with EMI in wireless systems, including electrical engineers, system designers and EMC scientists. In my opinion, if you are looking for a book on EMI in wireless system, this is the book to start with.

Antonio Orlandi (M’90-SM’97-F’07) was born in Milan, Italy in 1963. He received the Laurea degree in Electrical Engineering from the University of Rome “La Sapienza”, Italy, in 1988. He was with the Department of Electrical Engineering, University of Rome “La Sapienza” from 1988 to 1990. Since 1990 he has been with the Department of Electrical Engineering of the University of L’Aquila where he is currently Full Professor and Chair of the UAq EMC Laboratory. He is the author of more than 170 technical papers published in the field of electromagnetic compatibility in lightning protection systems and power drive systems. Current research interests are in the field of numerical methods and modeling techniques to address signal/power integrity and EMC/EMI issues in high speed digital systems. Dr. Orlandi received the IEEE Transactions on EMC Best Paper Award in 1997, the IEEE EMC Society Technical Achievement Award in 2003, the IBM Shared University Research Award in 2004, 2005 and 2006 and the CST University Award in 2004. He is a member of the Education, TC-9 Computational Electromagnetics and Chairman of the TC-10 “Signal Integrity” Committees of the IEEE EMC Society. He is Chairman of the TC-5 “Signal Integrity” Technical Committee of the International Zurich Symposium and Technical Exhibition on EMC. From 1996 to 2000, he has been Associate Editor of the IEEE Transactions on EMC and from 2001 to 2006 he served as Associate Editor of the IEEE Transactions on Mobile Computing. EMC

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