During DesignCon 2018, we took the opportunity to talk with Kenneth Wyatt, Senior Technical Editor for Interference Technology Magazine and EMC Consultant. He shared with us his vast knowledge of signal integrity, power integrity, and EMI.
0:07 What are your thoughts on this year’s DesignCon?
I’m enjoying DesignCon very much. I find it to be really a group of top-level engineers and that’s really what’s exciting about DesignCon. I’m just glad to be a part of it.
0:30 Can you elaborate on the challenging issues with signal integrity, power integrity, and electromagnetic interference?
Yes. I was honored to be part of the keynote panel on Tuesday. Our topic was what is it going to look like in five years as far as signal integrity, power integrity, and electromagnetic interference. There were five of us and I talked a little bit about what I thought the EMI situation was going to look like in five years and there’s really, there are several things that are coming that are going to be issues.
One of those is just the mere fact that there are so many wireless devices now that it’s starting to crowd the electromagnetic spectrum. I’m guessing that interference is going to be a bigger factor in the years to come with more and more communication systems and 5G cellular and all these new data communication systems. Spectrum management and interference, I think, are going to be key factors.
The other thing that I see is, in the area of autonomous vehicles, and not only automobiles, but there are major thrusts into farming, mining, transportation, both on land and on sea, and so they’re already working on autonomous ships and semi trucks. One of the stories that I told during my time was already in Colorado where I’m based, there was a test of an autonomous semi truck. It hauled 50,000 cans of Budweiser beer, from the factory near Fort Collins, through Denver, to Colorado Springs, to the distributor there, some 190 miles and it was all autonomous. Of course, they didn’t advertise that during the event but it did come out in the news last year.
Understand electromagnetic fields
Then, the other thing is, that I pointed out was that, designers don’t necessarily understand how electromagnetic fields move through circuit boards. There’s an aspect of education that we need to continue working on. For example, the last six clients that I’ve worked with have been trying to incorporate wireless technology into their products. The circuit boards contain onboard DC to DC converters that create a very broadband spectrum, out past a gigahertz. It desensitizes the cellular modem receiver, to the point where it’s not allowed on the telephone system. They designed this product and they can’t sell it, they can’t ship it. That’s been a problem. You really have to have a perfect circuit board design and locate these things away from the modem. There’s a number of design issues there that need to be thought about.
Education is a big deal. One of the challenges that I threw out to the group was, we, who really understand this stuff, attend DesignCon every year, but that knowledge is not getting out to the upper-level university students.
5:24 How do we educate the new group of designers into EMI and reliable designs?
Of course, there are some of us who conduct seminars but that only picks up a very small percentage of the designers out there. I know that DesignCon has bootcamp sessions, which is good. We need to keep doing that but even beyond that, the challenge I threw out to the group was that we who know this subject need to work more closely with the local universities and colleges. As an example, I’ve been working fairly closely with the University of Missouri, with their EMC program. I’m in touch with a lot of the students there and as I can, I give live presentations of what it is like in the real world as a product designer and as an EMC engineer. That’s some things we still need to work on.
6:34 How can the manufacturing industry assist in educating designers who are their customers?
Again, it’s important in all areas of manufacturing in the industry to partner with the local colleges and universities. I think that’s the best way. Of course, they can take in interns, but again, that’s just a small percentage of the population. We really need to expand the education beyond that. Things like writing articles for magazines, some of the industry publications might disseminate the information more widely, would be one example.
7:21 How do we fill the gaps in the knowledge?
That is tough, how do we impart this knowledge? The problem is, many of the professors don’t have practical experience in the industry. They’re sometimes reluctant to let people from the industry in to give presentations. It’s a tough question to answer.
7:50 Can webinars help in this area?
The question is can webinars and online training help? I think it can help. Todd Hubbing is a good example. He was the keynote speaker on Wednesday. Todd is connected with Clemson University and gives university courses online. He lives in Wisconsin and his students are literally all over the world. That’s a good answer to that probably.
8:28 What are your best advice on general guidelines and EMC practices?
That’s a big question. I have a two-day seminar on that topic. In a nutshell, a lot of the EMI issues revolve around the circuit board design. I’m incorporating more circuit design content within my seminars and basically, it is really important that for every signal layer, there is a signal return plane adjacent to it. If you don’t have that if you have a stack-up like signal, ground, signal, signal, power, signal. The top half signal ground signal is fine, but the signals reference to the power plane is, that was okay back in the 80’s and 90’s, but we’re decades past that and the clock frequencies are so fast now, that you can’t reference your signal to other than signal return. You need more ground return planes on the circuit board now.
Some companies are finally realizing that and I think more people here, attending DesignCon, understand that. It’s the designers in the trenches that don’t get out to DesignCon, that are having the issues, really.
10:13 It is a question of balancing the number of layers and economizing that aspect?
Yes, designing your circuit board and figuring out how many layers you need, there are trade offs there between cost and EMI performance, but we’re going to have to get used to the idea of paying more to get good EMI performance. Then, the other design thing that I am asked all the time is, what do you do with the cable shields? Do you ground at one end or both ends? It’s just basic stuff like that, that I try and teach and many others also.
10:52 When referencing your power plane, how do you account for that?
The return current is going to want to go back to the source, and a lot of engineers don’t understand that. The current’s flow in loops. If you reference to the power plane, it’s okay if that power plane is closely coupled to the actual return plane, or signal return. You can do that by close coupling if they’re closely adjacent, which works because there are built-in capacitors. Otherwise, multiple decoupling capacitors will help.
11:28 Are there any capacitors for very high frequency coming up?
Yes, the question is, are there other capacitor technologies that might work better than the standard ceramic multi-layer capacitors? The answer is yes. There have been inter digital capacitors and the X2Y type capacitor, with multiple grounds. Those do have much lower series inductance. It’s the series inductance that defeats the performance of a capacitor. Any way you can reduce that series inductance is important. Not only on the capacitor itself, but within the circuit board, you want many parallel paths, or wide short paths to where the capacitor connects. All those can help couple those two layers together more closely.
12:26 What’s your favorite part of this year’s DesignCon?
My favorite part of DesignCon, I think, I was honored to be part of the keynote panel on Tuesday. I was not expecting that. Other than that, I really enjoy speaking with the exhibitors and getting new ideas and seeing some of the new equipment that’s available as tools for both signal integrity, power integrity, and my favorite, EMI or EMC.
13:08 Why is DesignCon so important?
DesignCon is important now because the clock and data rates are increasing at such a fast pace that you really need to understand the physics of circuit boards now, and how to move signals from one place on the board to another. In fact, some of the most recent technology is, the answer is that you can’t do it internally to the board, you have to use jumpers and coaxes to get the signals from one side to the other. We’re talking 40 gigabytes per second kind of data or higher. That’s a challenge. This is one thing that DesignCon brings to the table is all the brain power that’s around the world, really, that congregates here are able to discuss these kinds of issues with each other and leverage each other’s ideas. That’s really important.
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