Issue link: https://iconnect007.uberflip.com/i/1483624
12 DESIGN007 MAGAZINE I NOVEMBER 2022 at means shorter rise times and more signal integrity problems, but when it comes to the SI problems and the impact the interconnects have on the signals, there are two ways of thinking about them: the circuit theory approach and the fields approach, which is really a transmission line analysis that's inherently distributed where the elec- tromagnetic fields are impor- tant. Barry Matties: When someone says, "PCB design is really just about physics," is there more to that statement than what you just described? Bogatin: When they say it's all physics, it's the electromagnetic fields described by Maxwell's equations and electromagnetic fields. ey're all synonymous in this context. It's correct that the way signals interact with interconnects is all electromagnetic fields and the boundary conditions—all Maxwell's equations. You don't have to be a PhD student to learn how to solve Maxwell's equations, but you must understand a little bit about electromagnetic fields, how they interact, and how they propagate. I had Professor Walter Lewin as a fresh- man at MIT, and I still vividly remember his lectures. Now there is a video series from his second semester freshman physics class, and he's got a million views. I use what I learned in his class almost daily. When I look at the videos, which are recorded 40 years aer I took the class, I see he hasn't changed at all, and the videos are timeless. I always recom- mend them. Holden: For people who are interested, are Lewin's courses suitable for those without electrical engineering degrees, but are inter- ested in understanding the principles? Bogatin: Yes. ey're offered to freshmen. You don't need to be enrolled in electrical engineering classes. ere's a little bit of math, but he goes through it slow enough that if you've had a little bit of cal- culus, you'd see it instantly. If you didn't, that's okay. It's only 25% equations. You still get the principles. Holden: Maxwell is not the easiest subject. Both Nolan and I were in electrical engi- neering, but because of the difficulty and the flunk-out rate from fields the- ory, we chose coding and stayed away from the RF and the fields. I just didn't have the math- ematical prowess to handle that. Bogatin: You're right. If you go that next step and talk about electromagnetic fields, Max- well's equations are differential equations, and you must understand some of that. What I like about Walter Lewin's lectures is he emphasizes the principles and the behaviors and doesn't let the math hide it. My students bring me his videos all the time. Most of the YouTube videos on understanding electromag- netics are bad analogies or they're not even the right physics. You're not learning something you can use to leverage other things down the line. Just for perspective, at MIT you get mechan- ics and electromagnetics in your freshman year. It's some math, but you get the heavy math in your junior and senior years. In my junior year, I took electromagnetics. We used John David Jackson's Classical Electrodynamics and it's incredibly heavy in the math. Holden: Is the abundance of heavy math instruction the reason why a lot of your focus has been on the rules of thumb and simplifica- tion in your books and publications? Eric Bogatin