“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