Three Book EMC/Signal Integrity Library

Would you like to have a mini-library on the subject of EMC and Signal Integrity that covers the frequency range from DC to light. The following three books, all highly recommended, will accomplish that. All the books are very readable, with a minimum of mathematics, and as a bonus there is very little overlap between the material contained in each of the books. I refer to all three of these books regularly.

Three Book Mini EMC Library

Electromagnetic Compatibility Engineering, by Henry W. Ott, published by John Wiley & Sons in 2009 has won the PROSE Award from the Association of American Publishers for the best book published in 2009 in the category of Engineering and Technology. It is the most comprehensive book on the subject and is the first EMC book that you should read. In addition to the core subjects of cabling, grounding, balancing, filtering, and shielding that made my previous book, Noise Reduction Techniques in Electronic Systems, an international success (translated into six other languages), this new book includes additional coverage of equipment and systems grounding, switching power supplies and variable speed motor drives, digital circuit power distribution and decoupling, PCB layout and stackup, mixed-signal PCB layout, rf and transient immunity, power line disturbances, and simple pre-compliance EMC measurements. Written in an easy to read and understandable style, it’s full of real-life practical examples. This book contains eighteen chapters, six appendices, and 872 pages.

High-Speed Digital Design, by Howard Johnson and Marty Graham, published by Prentice Hall in 1993 picks up where Electromagnetic Compatibility Engineering leaves off, with respect to high-speed digital circuits. Despite its title, this is more an EMC book than a classical digital design book. Its subtitle, “A Handbook of Black Magic,” gives away its true nature. Besides containing much practical information on the EMC aspects of high-speed digital design, the book also contains useful information on various measurement techniques that can be used to measure such things as power-ground plane impedance, metastable states, etc. Subjects include transmission lines, terminations, vias, clock distribution, clock oscillators, ribbon cables and connectors, layer stackup, and power distribution. This book is considered by many as a “crossover book” covering both EMC and signal integrity. Everything in this book is easy to read and practical. A “must have” book if you are designing high-speed digital circuits! This book contains twelve chapters, three appendices, and 447 pages.

High-Speed Digital System Design, by Hall, Hall, and McCall, published by John Wiley and Sons in 2000 continues where the Johnson and Graham book ends. This is a signal integrity book! It is very well written with a good balance between theory and practical applications. The first sentence of the book sets the tone of the book; it reads, The speed of light is just too slow. Subjects include transmission line considerations, crosstalk, IC package and pin-out considerations, power delivery and decoupling, non-ideal current return paths, simultaneous switching noise, timing and skew considerations, and radiation. The book also includes a chapter on design methodologies useful in the design of high-speed systems with a large number of variables. As does the Johnson and Graham book, this book  contains a chapter on high-speed measurement techniques. The information contained in this book is useful at both the IC and PCB level. This book contains eleven chapters, six appendices, and 347 pages.

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Want to expand your library by adding two additional books that fall on either end of the spectrum from the above three core books? Then consider the following two books:

Two Additional EMC Books

EDN Designer’s Guide to Electromagnetic Compatibility, Second Edition, by Bill Kimmel and Daryl Gerke, 2000 (originally published by EDN magazine in 1994), is a practical nuts and bolts approach to EMI, written for the non-EMI expert. One hundred pages of down-to-earth practical advice on EMC, without any equations or mathematics, by two authors who work regularly in the EMC trenches. The paperback book is available on the authors’ web site.

Introduction to Electromagnetic Compatibility, Second Edition, by Clayton Paul, published by John Wiley and Sons in 2006 is more theoretical than any of the other books, as it was intended to be used for a university course in EMC. A good book to get more detail on the theory behind EMC. Lots of useful information, especially the chapter on crosstalk, a subject that Dr. Paul is considered to be a leading expert. This book contains eleven chapters, four appendices, and 1016 pages.

So there you have it, three, (or possibly five) books that cover 90% of what you need to know about Electromagnetic Compatibility.

EMC Training in the Peachtree State

In partnership with IN Compliance magazine I will be presenting a three-day public Electromagnetic Compatibility Engineering seminar and EMC Exhibition in Atlanta, Georgia on April 17-19, 2012. This is the first time that I have presented this EMC seminar and exhibition in the southeastern United States.

This three-day intensive seminar covers the practical aspects of noise and interference control in electronic systems and provides a working knowledge of EMC principles.  Emphasis is on the cost-effective design of analog & digital systems. Commercial,  industrial, and military aspects of EMC are emphasized.  The amount and complexity of mathematics are kept to a minimum, and ideas are illustrated with examples of actual case histories. Participants will obtain the knowledge necessary to design electronic equipment that is compatible with the electromagnetic environment, and is in compliance with national and international EMC regulations.

Topics to be covered include:

Cabling

Grounding Principles

Digital Layout and Grounding

High-Speed Digital Decoupling

Differential-Mode Emission

Common-Mode Filtering

Digital Transmission Lines

Mixed-Signal PCB Grounding and Layout

RF and Transient Immunity

Conducted Emission

Shielding

This seminar is directed towards electrical engineers.  However, mechanical engineers, reliability and standards engineers, technical managers, systems engineers, regulatory compliance engineers, technicians, and others who need a working knowledge of electromagnetic compatibility engineering principles will also benefit from attending.

In addition to class notes, participants will receive a copy of my new 872 page, award winning book Electromagnetic Compatibility Engineering.

Registration is limited – so sign up early. Sign up by March 2, 2012 and take advantage of a $200 early registration discount. Don’t miss this great opportunity, click here for more information.

Electromagnetic Compatibility Engineering, Digital Edition

2012 is officially here, and I would like to wish everyone a happy and healthy New Year.

Ever since my new book “Electromagnetic Compatibility Engineering” was published in August 2009, I have wished for an iPhone/iPad compatible digital version so that I could easily carry the book around with me on my various business trips. At almost 900 pages, the print edition was not the most convenient book to carry on trips. Well for 2012 my wish has been granted.

Digital versions of “Electromagnetic Compatibility Engineering” are now available for the Apple iPad, iPhone, and iPod touch, as well as for the Kindle. The iPad/iPhone version is available from Apple’s iBook store, and the Kindle version is available from Amazon.com.

An e-book version, for your laptop or desktop computer, has been available since 2009 from the publisher (John Wiley). To see the range of digital versions available visit http://www.wiley.com/WileyCDA/WileyTitle/productCd-1118210654.html and look under Other Available Formats.

More information, as well as an errata sheet, on the book is available on my website http://www.hottconsultants.com/EMCE_book_files/emce_book.html.

Best wishes to one and all for the New Year.

Implementation of EMC Fixes

This post will discuss the last of my four tenets of EMC troubleshooting (see my 8/28/11 blog), Fix Implementation. When dealing with frequencies in the tens or hundreds of megacycle range, you are dealing with rf frequencies and cannot get sloppy in the way you implement EMC fixes. For example, if you believe that adding a capacitor at a certain point in your system will fix a problem, tack soldering the capacitor in with 2″ or 3″ leads, may work at audio frequencies, however, it will be completely useless at rf frequencies. The inductive reactance (impedance) of two half-inch long leads on a capacitor, at 200 MHz, will be about 20 Ω. Many times capacitor lead lengths must be 1/8″ or less in order to be effective.

Therefore, at the frequencies involved with most EMC problems, a fix must be implemented almost perfectly in order to be effective. This is often very difficult to do on an existing product, having many constraints. A poorly implemented fix can have no effect at all, thereby, leading one to draw the wrong conclusion and leading you astray.

I learned this principle many years ago while troubleshooting a 600 MHz emission problem. I was convinced that the emission was coming directly from one of the IC chips on the board. The IC was about one inch square. I fashioned a shield out of copper tape to cover the offending IC,  and grounded it to the PCB ground plane (with very short wires) at the four corners. The EMC measurements were repeated with absolutely no improvement, which lead me to believe that I was wrong about the IC being the source of the emission.

After 4 or 5 hours of trying all kind of other fixes, non of which worked, I (out of frustration) revisited my original idea that the IC was the source of the emission. This time a made a similar shield to cover the IC, but  grounded it at eight points, the four corners plus half-way along each side. Wala! The emission dropped 6 dB–problem solved!

Sometimes a fix cannot be implemented perfectly enough on an existing product. For example, if in the above case, there were no accessible ground points on the PCB to connect the shield to. In these cases you may just have to redesign the PCB, based on faith and knowledge that it is the correct thing to do, in order to implement the fix correctly. More often than not, it works.

This ends this series discussing the four basic tenants of EMC troubleshooting. Just understanding these four principles should make you a better EMC troubleshooter.

The “Kill it Dead” Strategy

In my 8/28/11 blog I listed the four basic principles of EMC troubleshooting, the third of which I will discuss in this post. This principle gets its name from a short one-page article written by Scott Roleson in 1992.* I often refer to this method as the “Giant Step versus Baby Step” approach to EMC troubleshooting. The analogy being, if I want to walk across a room, it will take me longer to do it if I take baby steps, than if I take giant steps.

When troubleshooting an EMC problem, especially on an existing product, the client always wants to make the minimal, least costly, change possible (taking baby steps). My approach is to do whatever is required to make the product compliant first, without regard to the cost or complexity (taking a giant step), then go back and refine the fix to be less costly and/or complex. In the meantime the product is compliant! Many times, potential EMC solutions are not tried because they are considered, at first glance, to be too complex or costly.

For example, let’s consider the case of radiation coming from a metallic enclose which has six different apertures. The “baby step” approach to troubleshooting this product is to cover one of the apertures with copper tape and then repeat the emission test to see if that solved the problem. Nope–that did not work, so let’s put copper tape over another aperture and repeat the emission test again, etc, etc, etc.

The “Kill it Dead” approach, on-the-other-hand, is to put copper tape over all the apertures and redo the emission test, in most cases the problem is now solved in one step. Then you can go back and see if the tape can be removed from some of the apertures without the problem reappearing. One should also see how this approach meshes with the Predominate Effect principal discussed in my  9/11/11 blog.

Another example might be, a four-layer PCB which has many traces that are routed over splits in the power and ground planes. A quick fix would be to add two more solid ground plane layers adjacent to the trace layers, a fix that almost always works but is costly since it makes the four-layer board a six-layer board. This also quickly proves the point that the traces crossing the splits in the planes are the problem. One can then, in many cases, cost reduce the fix by completely relaying-out the four-layer board to avoid the traces crossing the splits in the planes, and accomplish the same objective, without adding the two additional layers. This is a less costly but more time-consuming fix.

I think that you will find by taking the “Kill it Dead” approach, the time required to troubleshoot an EMC problem will be significantly reduced.

In my next blog I will discuss the last of the four tenets of EMC troubleshooting, Fix Implementation.

* Roleson, Scott, ‘The “Kill it Dead” Strategy,’ EMC Test and Design, September/October, 1992.

Predominate Effect

In my 8/28/11 post, The Four Basic Tenets of EMC Troubleshooting, I discussed the four basic principles, of EMC troubleshooting, the second of which was the Predominate Effect. In this blog I will discuss the significance of this principle.

An emission at any specific frequency is often caused by more than one source, and/or radiation mechanism– one of which is predominate and overshadows the others. If a fix is applied (such as a ferrite added to a cable, or reducing the size of an enclosure aperture) that decreases the magnitude of one of the non-dominant emission sources, and/or mechanisms, and the emission is remeasured–no improvement is seen, since the reduced emission is overshadowed by the magnitude of the predominate emission. This can lead to drawing a wrong conclusion, that is, that the fix had no positive effect. In order to notice an improvement, the predominate noise source must be fixed first. Therefore, in order to see an improvement, multiple noise sources must be fixed in a specific order–a difficult and time-consuming process.

Many times when troubleshooting I have applied a fix that reduced the emission, but not sufficient to bring the product into compliance with the EMC regulations. Then when I propose a second fix the client says: “No that does not work, I already tried that fix.” But the client tried it before I applied my fix, that reduced the emission, therefore, it probably was not the predominate effect at that time. My response is often “humor me and try it again,” and in many cases it is now effective.

There are basically two approaches to overcoming this perplexing Predominate Effect problem:

One is to always revisit old fixes that did not work, after an effective fix has been applied.

The second, and the one that I usually prefer, is to leave all seemingly ineffective fixes in place until the product is compliant, then remove them one at a time. Using this approach the removed fix, if it has an effect at all, will always be the predominate one. Any fix that does not increase the emission when removed, can now be eliminated.

Just understanding the concept of the Predominate Effect will make your troubleshooting less confusing and easier.

In a future blog I will discuss the “Kill it Dead” Strategy of EMC troubleshooting.

Divide and Conquer

In my 8/28/11 blog I discussed the four basic tenets of EMC troubleshooting, the first of which was Divide and Conquer. The objective of this approach is to eliminate some of the components, parts of the system, etc. from being associated with the problem, and then concentrate our troubleshooting efforts on the remaining components, parts of the system, etc. In this blog I will discuss this approach applied to the case of a radiated emission problem, and the case of a conducted emission problem.

Radiated Emission Problem. In the case of a radiated emission problem it is advantages to determine if the emission is coming from the cables, or from the enclosure/PCB. Often the simplest way to do this is to remove the cables and see if the product passes without cables. If it does, the emission is coming from the cables. If not, fix the enclosure/PCB first, then worry about the cables. If the product does not pass without cables, it will never pass with cables.

Of course, when removing the cables, you cannot remove the power cable. Therefore, wrap the power cable around a big ferrite core to suppress the radiation from this cable.

Another approach, not requiring the removal of the cables, would be to measure the common-mode currents on the cables using a common-mode current clamp such as the Fischer Custom Communications Model F-33-1, or if the emissions are above 250 MHz, the F-61 current probe. See Measuring Common-Mode Currents on Cables.

Conducted Emission Problem. The first thing to do when facing a conducted emission problem, on the power line, is to determine the frequency of the failure(s). If it is at the low end of the conducted emission spectrum, the source is most likely the switching power supply or an ineffective  power line filter. If the failure is at the high end of the conducted emission spectrum, the source is most likely the digital logic.

If the emission is from the switching power supply, it is desirable to next determine if the emission is from a common-mode or a differential-mode noise current – since different components in the power supply, and the power-line filter, affect differential-mode emissions and common-mode emissions. Performing the conducted emission test as specified in the various EMC regulations, will not determine this.

We can, however, determine this by adding a differential-mode rejection network between the LISN and the measuring instrument. This will allow us to determine the magnitude of just the common-mode noise, see Distinguishing Between CM and DM Conducted Emissions.

If you make a habit of dividing up your EMC problems as discussed in this blog, your EMC troubleshooting will be easier and will go much faster.

In my next blog I will discuss the Predominate Effect principle.

The Four Basic Tenets of EMC Troubleshooting

The lull in the middle of the storm! As I write this I am sitting at home in the eye of hurricane Irene, the rain has stopped, the wind has stopped, and the sun is almost out. In the last 10 hours we have received over 6″ of rain. I know, however, that we have at least another 8 hours of torrential rain and hurricane force winds left before this thing is actually over.

At my presentation as part of the Consultant’s Workshop at the 2011 IEEE EMC Symposium in Long Beach, CA on Friday August 19, I talked about the four basis tenets of  EMC troubleshooting. If you understand these four basic principles, your EMC troubleshooting will be a lot easier and will go a lot faster. The four tenets are:

• Divide and Conquer
• Predominate Effect
• The “Kill it Dead” Strategy
• Fix Implementation

My next few blogs  will cover each of these basic principles individually.

2011 IEEE EMC Symposium

I spent last week at the 2011 IEEE EMC Symposium in Long Beach, CA. It was an excellent conference with a number of very interesting papers being presented. It also provided an opportunity to chat with many old friends that I get to see only once a year. I organized and chaired the Fundamentals of EMC Session on Monday, which had attendance approaching 200. I also gave a presentation on “Dipoles for Dummies” at this session. In addition, I did a presentation at the Consultant’s Workshop on Friday afternoon, where the attendance was around 50. The exhibits and social events were also interesting and well attended.
The above photo is of me operating W6RO the Amateur Radio Station on the Queen Mary, the venue for the Wednesday night gala social event where over 750 symposium attendees had cocktails, dinner, and were entertained on this historic ship.

Public EMC Seminar

In partnership with In Compliance Magazine I will be presenting a three-day public EMC seminar in Austin, TX, October 25-27, 2011. For more information go to www.hottconsultants.com/public.html.