“Bogatin’s Practical Guide to Transmission Line Design and Characterization for Signal Integrity Applications” – A Review

Everything you ever wanted to know about PCB transmission lines – and more – in a digestible format with just the right amount of math to back up the illuminating practical illustrations.

Ed.: Martyn Gaudion is managing director of Polar Instruments Ltd. He began his career at Tektronix in test engineering on high-bandwidth portable oscilloscopes. He joined Polar in 1990, where he was responsible for the design and development of the Toneohm 950, Polar’s multilayer PCB short circuit locator. He became CEO in 2010. He also develops tailored content for the Polar YouTube channel. He reviewed this book for PCD&F.

Hot off the virtual press – a copy of Dr. Eric Bogatin’s new guide to transmission line design appeared in my Artech eBook account.

Do we really need another transmission line book? That’s what Dr. Bogatin asks right at the outset. After reading this new tome from virtual cover to cover, yes we do. This is a thoroughly practical book an peppered with links to Bogatins’s brief informative video explanations which expand and add dynamic content in a way that printed matter alone cannot.

Whether you are a recent graduate who wants a more practical insight to the behavior of transmission lines after doing all the hard work of the pure math side of study, or an experienced electrical engineer moving into the high speed arena – or even a PCB technologist or fabricator wanting an insight into all the mysterious terminology that surrounds the subject – this is a resource book for you. It is equally valuable whether you are dipping into chapters of specific interest, or taking a deep breath and reading from (virtual) cover to cover.

In my day job I spend most of my time helping customers who are new to transmission lines ensure that they document and design them correctly for fabrication, and I confess over the years much is taken as given. By reading Bogatin’s new book I have gained insight into transmission line behavior that is very familiar but I didn’t know the why – and the why makes everything make more sense. 

It is staggering that the electrical behavior of a simple pair of copper traces with a sandwich of dielectric material can generate a book running to 600 pages without loss of interest, but this is exactly what Bogatin does with the subject. Along the way you will find out why you should always think of signal and return paths and not in terms of signal and ground. You will find that while the RF and digital design spaces may run at similar frequencies, the design considerations for both are poles apart. (No pun intended.) You will also discover that simulators and field solvers don’t design circuits – you do – and you best have an idea of what you intend to happen and the expected outcome before reaching for the simulator. Words are important, and Bogatin stresses that though digital and RF and EMC specialists all deal with high-speed signals – and a lot of the jargon is similar – there are often situations where technical terms overlap while their meanings don’t. Bogatin takes an important stance in defining and understanding the terminology to ensure you are understood when working across disciplines.

On measurement – there are many precision tools for measuring high speed signals and time and frequency domain information, all with accuracy beyond your dreams – but as with simulation – Bogatin cautions that unless you understand what you are measuring and how to design your test vehicle, any or all of that expensive equipment can lead you to the wrong answer. Time spent in the measurement section of the book is well invested and will enable you to extract the best possible measurements from whatever TDR/sampling oscilloscope/vector network analyzer you have to hand.

I personally like the examples where Bogatin mixes electronic timescales in nanoseconds with human relatable timescales (days) to bring tangible meaning to his explanations. I also like his informative section on why intuition in the frequency domain does not translate easily (at all?) to the time domain, and that while both are valid and useful you need to work with a degree of selective schizophrenia while working in these domains.

Last but not least, alongside the video links and examples are links to both evaluation versions of commercial tools and useful no cost utilities so you can run the simulations and experiment for yourself.

Martyn Gaudion, June 2020

Bogatin’s Practical Guide to Transmission Line Design and Characterization for Signal Integrity Applications

by Dr. Eric Bogatin

Available from Artech House

Remembering Gene Marsh

Gene Marsh, one of the true industry pioneers, has died.

Marsh, as many readers may recall, founded PADS Software, one of the first CAD software developers, in 1977. In fact, he beat Mentor’s, Cadnetix’s and Daisy’s respective founders to the punch by four years. (1981 was a big year for CAD, as it turned out.)

Gene was such a big deal, Printed Circuit Design started an award for software innovation and named it after him.

While Gene has been out of the industry for years, this is still a sad day.

PCU’s Top 10 of 2011

Here are the 10 most-viewed items on Printed Circuit University in 2011.

1. Essential Principles of Signal Integrity
2. Advanced Signal Integrity Design
3. High Speed Symposium
4. Differential Pair Boot Camp
5. Getting Started with SI
6. A High Speed Design Methodology
7. What Is High Speed and Why Should I Care?
8. Controlling Transmission Line Loss Boot Camp
9. High Performance Multilayer PCBs
10. Separating Myth from Reality in Signal Integrity.

As always, thanks for watching!

Time Keeps on Ticking, Ticking …

Twenty years? PCB West is 20 years old? I feel like Rip Van Winkle all of a sudden. I close my eyes, take a walk around the block and poof, those years have flown by. And at the risk of dating myself, I was barely in my forties when we started PCB West. (You do the math.)

It only seems like a long time when I think about some of the shows and things that happened back in the heady days of the 1990s. Then there are some photos floating around of those early PCB West shows. Looking at those pics, I can see I’m not the only one who has aged a bit. And speaking of age, in some ways the PCB design world has also aged. I’m sure some of you remember the PCB Benchmark that we used to do at PCB West. Back in those days, it was not unusual to have more than a dozen different EDA vendors participating in the benchmark. Today most of those companies have been gobbled up by three or four companies. During the days of the first PCB Design Conferences, personal computers were just coming into wide use. The DOS OS was still limited by hardware and software, and most design systems were still operating on UNIX-based machines from Sun or HP. By comparison, I expect any day to hear of some EDA company releasing a product optimized for the iPAD.

In the early days as editor of Printed Circuit Design magazine, I used to talk about the Buck Rogers syndrome: When I was a kid, everyone expected us to be walking on Mars and riding around in flying cars by the year 2000. It’s what we saw on TV and what a country and society that knew few boundaries could imagine. While we may be a bit more realistic about expectations these days, the pace of change has accelerated. Think about this: When we started the PCB Design Conference, there were no cell phones or laptops (at least not for the masses), and we didn’t even imagine email or the Internet.

The technology has changed over the years: finer features, many more pins on the components, and signal integrity issues are the norm. But, basically, it is the same process. In some ways PCB design has changed a lot in 20 years, but in some ways it is still the same. In my mind it’s a lot like the people involved. You’ve changed in some ways to keep up with the technology, but in the end, PCB designers are still the ones who turn that idea, that concept, into a tangible product. To me that means you are still the indispensable link in the chain.

Thanks for all you do, and thanks for the first 20 fantastic years of PCB Design Conference. We couldn’t have done it without you.

PCB West is Back!

Registration is open for PCB West, our annual conference for printed circuit board design, fabrication and assembly.

We have more than 50 presentations at this year’s show, which takes place Sept. 27-29 at the Santa Clara, CA, Convention Center. As with last year, several sessions on the exhibition day, Sept. 28, are free.

A big shout out to the SMTA Silicon Valley chapter, which put together the assembly tracks. Some of the proceeds will benefit the chapter.

Mark your calendars — and don’t forget to register!

PCB West: Back for More!

Registration is open for PCB West, our annual conference for printed circuit board design, fabrication and assembly.

We have more than 50 presentations at this year’s show, which takes place Sept. 27-29 at the Santa Clara, CA, Convention Center. As with last year, several sessions on the exhibition day, Sept. 28, are free.

A big shout out to the SMTA Silicon Valley chapter, which put together the assembly tracks.

Mark your calendars — and don’t forget to register!

PCU Goes Live!

As “Dean Pete” (I think Professor Pete sounds better) intimated earlier today, we have just gone live with Printed Circuit University, the industry’s first online e-learning and training resource for professionals involved in the engineering and design of printed circuit boards and related technologies.

Printed Circuit University is built on the robust, established and time-proven beTheSignal e-learning platform, and features instruction by SI guru Dr. Eric Bogatin.

Pete and VP of Sales and Marketing Frances Stewart are demonstrating Printed Circuit University this week at DesignCon in the Santa Clara. Be sure to stop by and take a look at what promises to be the future of printed circuit board design education and training.

Does Angle Matter?

It’s standard practice to avoid joining small PCB traces at 90 degrees, but instead to join them at an angle. But does it matter for thick traces?

Right angle traces

Above and below are some 0.020″ or 0.024″ traces. Is it really going to matter, with a pad-size trace, what angle the joining trace hits the other one?

Convention would have you do something like the alternative layout below. Either like “A” or like “B.” But, is it really necessary and worth the extra time required to do that?

Not right angle traces

Part of me really wonders and another part of me says, it shows attention to detail and implies that the entire design was produced with the same care. It’s that elegance in design thing.

The other question I have relates to “B,” in the bottom image. Does it matter which direction the 45 degree trace intersects? Does it matter based on the direction of current flow or does it matter at all?

Which of the three illustrated techniques do you prefer and use?

Duane Benson
Winslow Leach says hi.


Standards, How They Should Be Done

This week at the annual GSMA Mobile World Congress, 17 of the top mobile operators and manufacturers agreed to adopt Micro-USB as the universal charger interface for new mobile phones.

The initiative, says GSMA, centers on having a universal charger interface by 2012. The group further agreed that the majority of chargers shipped at that time will meet the high efficiency targets set out by the OMTP (Open Mobile Terminal Platform). The move could reduce the number of chargers built each year by as much as 50% — a whopping half a billion units.

“The mobile industry has a pivotal role to play in tackling environmental issues and this program is an important step that could lead to huge savings in resources, not to mention convenience for consumers,” said Rob Conway, CEO of the GSMA. “There is enormous potential in mobile to help people live and work in an ecofriendly way and with the backing of some or the biggest names in the industry, this initiative will lead the way.”

This is great news for consumers, who will no longer have to ditch their working chargers every time they upgrade phones.

The initial group of companies that have signed on include AT&T, LG, Motorola, Nokia, Qualcomm, Samsung, Sony Ericsson, T-Mobile and Vodafone, among others. There are a couple big exceptions: Apple and RIM, so far, are not playing ball.
Here’s hoping they eventually enter the fold.

But what’s really nice to see is the number of competitors working together in a way that should lower the end-product and usage costs for the consumer while also enhancing the convenience, all while ensuring millions of old chargers won’t be headed to the world’s landfills. That’s what good standards development should do.