EMC on the Board and Off the Board

We are very delighted to have Min Zhang in this episode. Min is an independent EMC consultant based in the UK. Today, we'll be talking about EMC, both on board and off the board. It will be a very interesting discussion because we will look a little bit deeper at the system level.

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Show Highlights:

• Zach met Min at EMCLive 2021
• Let’s hear more about Min’s background and his early exposure to EMI issues
  • Earlier in his career, he worked with big companies as a motor drive engineer and power electronics design engineer for 10 years
  • He started his engineering consulting business, Mach One Design EMC Consultants 2 years ago
  • His first experience dealing with EMI issues was at the university while doing research for his PhD
• The lack of education in the university in regards to EMI issues is one of the reasons that sparked Min’s interest in EMI
  • The university he went to specializes in motor and power converter design, but did not offer any solutions in fixing the EMI issues
  • Min recalls being fascinated by his first time seeing an EMI diagnosis kit composed of the spectrum analyzer, lots of ferrites, and cable shooting copper tape in a suitcase
  • It was his first time seeing a step-by-step diagnosis and troubleshooting EMI issues - checking the grounding, checking the bonding, and applying ferrites at the right place, performed by his friend’s father who was then a principal engineer in the European Space Agency
• Min’s recommendation to design engineers solving EMI issues is to understand the fundamentals – “only when you understand the fundamentals, understand the basics, and the first principle, then you can really design a system” - Min Zhang
• What happens when EMI problems exist off the board and they interfere with the system or create so much noise that the system is never going to pass EMC?
  • Min answers by recommending Rick Hartley's famous YouTube video about grounding
  • He continues with his answer with an example involving a three-phase brushless DC motor drive
• How to deal with cables connected to another system that is outside of the shielding?
  • Shielding is a good solution, but understanding fundamentals are necessary to avoid increased cost, weight, and also the bending ratio would be affected
• Min shares a recent video he did with Robert Feranec which discusses the topic of EMI troubleshooting on immunity
• 70% of the EMI issues are somehow related to resonance
  • For high-speed design, PCB designers really need to understand how the wave propagates
• Ferrite is not a 100% inductive component
• Min recommends the book by Douglas Smith – High Frequency Measurements and Noise in Electronic Circuits which focuses on the test and measurements in terms of high-speed design
• Other experts to learn from in terms of EMI troubleshooting and high speed designs are Eric Bogatin, Steve Sandler and Heidi Barnes

Links and Resources:

Learn more about Min Zhang and his company Mach One Design EMC Consultants
Watch Min’s Keynote at EMCLive 2021
Watch How a Few Components Make a Big Difference in EMC/EMI with Min and Robert Feranec 
Read Min Zhang’s article on SI Journal
Great book recommendation: High Frequency Measurements and Noise in Electronic Circuits
Watch Rick Hartley's famous YouTube video about grounding
Watch previous episodes with EMI and High-speed experts:
    Eric Bogatin Debunks Common Misconceptions About Transmission Lines
    Secrets of PCB Optimization with Rick Hartley
    Being Right Matters! When, Why and What to Simulate with Steve Sandler
    Power Integrity and Simulations with Heidi Barnes

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Min Zhang:
What I found in the field is even using multiple stage filter, you are quite successful in suppressing noise between the lower frequency range as we discussed but for higher frequency, that is less effective. But if you look at the power application, there is no such device that works effectively all the way to more than 30 or 40 megawatts.

Zach Peterson:
Hello everyone and welcome to the Altium OnTrack podcast. I am very happy to be speaking with Min Zhang today, independent EMC consultant based in the UK. Today, we'll be talking about EMC, both on the board and off the board, and I think it will be a very interesting discussion because it lets us look a little bit more at the system level. Thank you so much for joining us today.

Min Zhang:
It has been my pleasure Zach.

Zach Peterson:
Yes. So I believe the first time we had been involved in the same event, but had not, I don't think, actually had a chance to speak to each other was at an EMC live event last year. You were talking about EMC in automotive and I was talking radar so little bit, a bit of worlds apart here but it's actually nice to finally talk to you directly.

Min Zhang:
Yeah. Same here.

Zach Peterson:
Thank you. So with you being newer on the podcast, maybe you can introduce yourself to the audience and then maybe describe some of your experience and then how did you get into the EMC world?

Min Zhang:
Okay. Yeah. So yes. Thanks for the brief introduction. So I have been running a very small engineering consulting business but mainly focusing in the field of EMC for just about over two years now. Before that, I have been working for big companies as motor control or motor drive engineer and power electronics design engineer for more than, I think, eight or maybe 10 years. It depends on how you count it.

Min Zhang:
Before that, I was in the university doing research. So I completed my PhD and the topic is about a switching scheme on a three-phase, four-leg voltage source inverter and that was, I think, the first time I really looked into the EMI issues particularly related to how you switch the converter and how fast the impact could be in a system level like that.

Min Zhang:
I think lots of people who listen to this podcast, at one point, would have EMI issues because that's just an inherent problem with designing either a PC or [inaudible 00:03:14] system. It has always been a challenging task, I guess. Lots of people treated it as black magic or dark arts. I think lots of experts have explained about this issue. So basically, it's a combination of lack of education in the university and also some old way of thinking, following a do's and don't list actually. Those lists probably is wrong considering how fast the modem switches goes and modem system is.

Min Zhang:
So I got interested in the field of EMC mainly because it was in the university. When I was doing my PhD, I have my best friend Andrew. He has a very good project to work on. The project is about monitoring the capacitor, I guess, the charging-discharging performance and using that information to predict the failure of a capacitor. It's useful for tolerant application in aerospace. His research has been going on well in terms of the simulation works, the low voltage rig works. But when he was trying to implement in a high power, high voltage rig, it simply couldn't work simply because of the huge noise source that is involved because it is a motor drive system. And as you can imagine, when the converter start driving a big power motor and you get noise everywhere.

Min Zhang:
Because our university is specialized in motor and power converter design, we got the best professor in the field. But I was really surprised to see that even the best lecturer and professor in the field had no solution in terms of fixing the EMI issues. So that was the time when I realized okay, so this is a serious problem.

Min Zhang:
I got interested in it and the problem, my friend's problem was eventually solved was the help of his father, actually. His father worked as a principal engineer in the European Space Agency so he had, really, to fly from Holland, at the time, to the UK and bringing him a special case. I still remember that suit case which involves a spectrum analyzer, lots of ferrites and cable shielding copper tape. That was the first time when I saw proper a EMI diagnosis kit myself and I was so fascinated about it.

Min Zhang:
And actually, it was a weekend. I remembered. I was really just observing how his father took a step-by-step approach to fix the issues. That was the first time I saw a proper EMI diagnosis or troubleshooting process including checking the grounding, checking the bonding, and apply ferrites at the right place. Yeah. Lots of things using copper tape. So I guess that event, that single event really sparked my interest in the field. So since then, yeah. I've been working intensively in this field.

Zach Peterson:
So this is very interesting because you said something that, well, pretty much every old school, high-speed designer has said which is that, the old do's and don'ts list or the old rules of thumb stop working because the system runs so fast meaning edge rate. But you're really saying the same thing in terms of EMC and EMI. I know that the two are related, of course. I think not everybody does but it sounds almost like you're implying that the best design practices, possibly, for high-speed digital really are actually best EMI/EMC practices.

Min Zhang:
Yeah. I guess you can. You can safely so. Obviously, now the EMC, subject of EMC now expanded to not only limited EMC but also CP as signal integrity and power integrity. I guess that's where lots of our engineers are focusing at the minute, high speed design and things like that.

Min Zhang:
But the strange thing is lots of people find me as a very practical guy solving EMC issues. But actually, if there's any recommendation I could give to a design engineer that would be really understand the fundamentals because only when you understand the fundamentals, understand the basics and the first principle, then you can really design a system.

Zach Peterson:
Yes. Absolutely. I think that's one of the reasons that ... I guess in the videos that I make, some of those questions that we get really always go back to some of those same fundamentals. I think it's one of those things where you have to look at it from 10 different perspectives until you can actually suss out what is the right approach that can help you address many of those issues.

Zach Peterson:
I've found it. Most of the easy EMI problems to solve relate to stackup-defining ground, so grounding like you've said, and then routing properly. A lot of the easy stuff can be solved that way which might be 50% or 75% of problems. But eventually, the problems span beyond just how did I route this trace on the board? It seems like you're looking also at all of those other problems because I'm sure they're related to how you create the circuit board and with the stackup and everything. But at some point, they exist off the board and they interfere with the system or they just create so much noise that the system is never going to pass EMC.

Min Zhang:
Yeah. That is a good point. Actually, I have a good case study here to show. So exactly as you said. If we look at a PC, just a bare PCB board design, then apply all the techniques like stackup, rooting, and future design, if you design a [inaudible 00:09:55] properly, that would probably contain the noise on the broader level.

Min Zhang:
Then, the next challenge is if you have multiple boards in a system level, then you will always end up with connectors and cables between PCBs. That starts another issue. Basically, where is your ground? Because we are very familiar with the topic of one ground. I think lots of people have been quite familiar with this topic if they watch Rick Hartley's famous YouTube video about grounding, two-hours long, so that's all talking about ground in a PCP level. But then when you have three or four PCPs and then they interconnect with data lines, power lines, signal lines, and they all have different zero volts, let's say, let's just make sure that's ... Yeah. They are not really ground ground but zero volts. So you will always end up with high frequency potential difference between the two or three zero volts.

Min Zhang:
A typical example, actually, is if you look at motor drive application, let's say. If it's a three-phase brushless DC motor drive, making it simple, you have a converter circuit and you have a motor. So in this case, we often treat the zero volts or grounds in a system as the negative DC link bus. So if you have electrolytic capacitors connecting between positive DC and negative DC, then that negative DC is often considered as the zero volts reference or ground reference.

Min Zhang:
Then, of course, you have three half bridges and then in the middle point of these half bridges, you're connected to the three phase winding of a motor. But then this happens. What happens was the motor itself is floating compared to this zero volts. Then you ended up with lots of noise and that's a typical motor drive application noise. It has always been a problem because it's [inaudible 00:12:15] band and it's everywhere and you just need to suppress it.

Min Zhang:
So one effective way, we found, is to ground the frame. So when we say ground the frame, in a much larger system you might find, actually, so you have the converter bonded to a common chassis plane, and then perhaps two or three meters or even 20 or 30 meters away, you have the motor frame bonded to the same chassis. So that's basically just trying to make sure that the two reference points have more or less the same potential so that will often work.

Min Zhang:
But as we talk now, even motor drive circuit used to be the case of switching frequency, five kilohertz, IGBT. That's just the standard technology back 10 or 20 years ago. Modern days, we have silicon carbide or gang devices, which switch much faster with a lot faster rising and falling time. Then using the same trick, running a long distance will give you lots of trouble and you probably won't be able to solve the EMI issues. So in this case, we really need to treat things differently in terms of design.

Zach Peterson:
So this is a good topic to bring up because now we're talking about the fundamental change in the actual circuit itself. You mentioned a switch from IGBT to eventually [moss vets?] and now silicon carbide and GaN which is not just a motor drive thing. It's now, also, an RF thing so finding those components or finding a home in multiple places.

Zach Peterson:
But what actually needs to change in that type of application where you have, as you say, maybe the motor drive or the motor is far and away from the actual control board. And in this case where let's say you have the control board and its power system and maybe there's a digital subsystem or whatever, I think it's easy to shield the boards. Right? Like you say, maybe you put them in the chassis to shield the chassis, or whatever it is, and it's connected to a frame ground. You've got a safety enclosure around that and those boards. But what then happens with something that is running out of a cable and is connected to, like you say, maybe it's a motor, maybe it's some other system that's outside of the shielding. What do we do about that?

Min Zhang:
Yeah. So this is a very good question because ideally, with modern technology as we just discussed, you would always want to put the converter next to the motor. That's perhaps the easiest and the most efficient way of solving our problems. But applications, that's basically what determines your configuration or your topology is always the product application. There are some applications where you simply cannot put the converter next to the motor. For instance, if the motor is a small size motor, put in a very tight space in a product and they have to use long cables so that's becoming very, very challenging, as you said.

Min Zhang:
We can always run a gardening cable next to the motor face wire but that's not effective, as we discussed, with the high frequency stuff. Shielding is a good solution. So not only do you need to shield the converter side, meaning mainly to connect that shielding end to the zero volts reference, as we discussed, which is often the negative DC link. You also need to connect the shield to the motor frame. So that's easier said than done because the shield would increase cost, weight, and also the bending ratio would be affected. Sometimes if you are not terminating it properly, you ended up with still bad product so that's the challenge we're facing at this stage. Because as I said, if you understand fundamental, you will know that now in this case, the cable with linking the converter and the motor becomes a transmission line because it's just very long and you really need to think carefully when you design a system as this. Yeah.

Zach Peterson:
So you brought up a couple of good points here because you're talking about noise pick up on a cable. I think most designers who may not be familiar with this particular application will hear oh, noise is being picked up on a cable. Well, I need to attach like a ferrite choke to it or a ferrite ring to it. You look at power cords, let's say, coming into your computer or whatever and they have one of those on it. So I think it's easy to say well, it works here so it should work there as well. Tell me what's wrong with that thinking or is that the right thinking in this case.

Min Zhang:
Good question. I think that thinking is still valid. It's valid thinking, Yeah. Again using the same case study, the motor drive control, let's say, there are actually two challenges here because even with the fast switching devices such as silicon carbide and the gang device, the majority of the noise that the motor drive circuit creates is due within the range of a few hundred kilohertz up to a five megahertz. Then, of course, the noise profile will be seen in a much higher frequency range.

Min Zhang:
The challenge here is you can always design a good filter on your board. For example, you could design, for a three-phase motor you could design a three-phase LC filter and you might say okay, that's not enough. Let's design a three-phase LC filter. That's as a first stage. And then after that, we are going to have a three-phase common mode choke plus some Y caps so that would be serving high frequency filtering as the second stage.

Min Zhang:
But what I found in the few days, even using multiple stage filter, you are quite successful in suppressing noise between the lower frequency range, as we discussed. But for higher frequency, that is less effective because if you look at all the data sheets of say common note choke, because again, this is used for a high power application. We're not talking about a CAN bus design because, for example, a CAN bus design, they're always common note choke which works quite effectively beyond hundreds of megahertz. But if you look at the power application, there is no such device that works effectively all the way to more than 30 or 40 megahertz.

Min Zhang:
So often, we've found, actually, the ferrite technique still works because that's a very effective way of suppressing the noise at 100 or 200 megahertz. So you ended up having properly designed a filter on the board that is mainly designed for suppressing the noise in the lower frequency range and then a ferrite that would suppress the high frequency range noise.

Zach Peterson:
That's what I was hoping you were going to say. It's not just one component that's like the magic bullet for every single noise source because the noise is broadband. You have to think about what do I do to attack the high frequency range? That's the ferrite application.

Zach Peterson:
The low frequency range is much better attacked with a filter, as you've said, like a filter circuit. And then, it seems to me though that even if you have these elements in the system whether it's a ferrite on the cable or whether it's a filter on the board, it's still beneficial to maybe do something to try and prevent the noise pickup on a cable in the first place. And when we talk noise pickup, I mean there's the conducted noise that's transmitted over the cable. But then there's the possibility, also, of receiving radiated emissions in the cable and then that transmits into the circuit as well. Do we really care about the fact that the cable picks up noise or if it's really extreme, do we then have to say well, okay. We have to shield this cable and apply some shielding throughout the system.

Min Zhang:
Again, it depends on your application. Lots of the products I worked with are automotive products so there were standard practice in the automotive field. So they will always try to use shielding and the box they developed is always like sorted metal enclosure with gas kits, making sure that the lid and the box is really suited in terms of RF.

Min Zhang:
Then, as you said, they would focus both on the board design which is filter and then they also need to focus on the connected design especially when the cable goes into the connector and then connecting to the PCB. That little bit of area is often overlooked by the engineers. So in those kind of applications, you are using a shielded cable so you really do risk your product in terms of radiation emission particularly.

Min Zhang:
So that's really good practice but not every products' application uses, as I mentioned, if you work in a sort of home appliance application where own cost is really the determining factor in your design and perhaps, as I mentioned, the cost, the weight, and the bending ratio of the cable. All these constraints basically means you can't use shielded cable. Then you really need to rethink the approach when it comes to cable and [futuring].

Zach Peterson:
So I heard you bring up the issue with like a bond cost. I think this is an area where that transition to high volume, especially in an area like consumer appliances, that is something that could go or create constraints that oppose maybe some of the best practices in EMI/EMC and can drive designers to do things that then compromise the system. Maybe it is reducing layer count, maybe it's compromising and going for lower quality components because, I mean, it's understandable. Right?

Zach Peterson:
You're going to produce a million devices. That extra dollar that you might spend on a better common mode choke, let's say, or whatever it is or a transformer or whatever, that adds up when you're producing a million devices a year so I think there's a big incentive for companies to do whatever they can to try and reduce some of those costs. What would you say is maybe a better strategy to ensure that you do get a compliant product without just compromising on component costs and aiming for the lowest component cost? Is there something that needs to happen maybe on the design side that maybe it makes the design more difficult or more complex but is actually beneficial and can allow you to maybe use a lower cost component if it does require this level of noise suppression that we're talking about?

Min Zhang:
That's a very good question Zach. I think there's, again, another interesting story to share. I recently did a conversation with Robert Faranick on YouTube. It's about EMI troubleshooting on immunity.

Zach Peterson:
I did see that and I just want to tell the viewers we'll actually link to that in the show notes so I would encourage anyone to go watch it because it is an interesting conversation. Sorry. I didn't mean to interrupt. Please continue.

Min Zhang:
Yeah. So that's exactly what we're discussing now because it is a company that makes some beacon fire alarm product and they are not really large volume manufacturers. But, of course, being a small and medium company, one course is also a very big design concern when they design products and because of the supply chain disruptions we are all facing, I think everyone I spoke to had the same issue. They ended up having to select a new platform. But, of course, redesigning the whole system comes at a cost. So to really avoid redesigning the whole system, what they came up with was just designing a daughter board with a new chip on top and then they sold the daughter board to the old motherboard PCP and by doing so they thought there's really no risk.

Min Zhang:
So they sent the board for immunity test and then it failed immunity test. It was a really, really good troubleshooting case for me because I knew they cannot afford to use expensive materials or expensive solutions in that case. So really, the task is how to find the lowest cost solution for the application and we were lucky. We lucky in the end. We found a ferrite plate which happened to have exactly the same pinout to their daughter board. So then, putting that ferrite plate in between the two boards, we solved the problem.

Min Zhang:
It's also an interesting case study because that's just demonstrates a very good point in terms of EMI troubleshooting. I would say 70% of the EMI issues are somehow related to resonance. We talk about cable resonance. You've got resonance between PCPs and if you have a fully-enclosed box, you probably will have a cavity resonance. And then, if you have two large systems installed on a factory site and then linked with power cable or signal cable, then you've got these two systems basically have resonance so lots of resonance issues in the field EMI/EMC.

Min Zhang:
So if I want to give advice to manufacturers in general is when you do a design, don't rush because in that case, the company rushed to manufacture thousands or 10 thousands of these little PCPs so there is really no way back. So my advice would always be to look at the system and review it and when you review the system, you should take the EMC into consideration. At least you should know there is a potential risk associated with this new change. And when you do the risk analysis, you put the risk, you put the likelihood and then you put some solutions just in case. Right? So often, fingers crossed, we don't have any issue but if there is an issue, do you have the solution for it? Or if you don't have the solution for it, do you have anybody in your contact list that you can quickly contact to make sure that this person is available to solve your problems? So these is the advice I would give to manufacturers in general.

Zach Peterson:
So the case that you just described sounds really interesting because I think it's one of those things about resonance that even if you know about it, in terms of the structure of a PCP, it's still something that can happen, in this case, as we're talking, in the system.

Zach Peterson:
It sounds like the resonance in this case was between two boards because you had a daughter board. And so, you create, essentially, an open on the edges, resonant cavity that's bounded by two surfaces. So I think the takeaway there, in terms of what the solution was, is that by adding the ferrite plate between the two boards, as you described, I think that's how you described it, essentially what you've done is you've pushed those lowest order resonances up to much higher frequencies. And so, now the dominant noise frequency range where the noise is being generated can no longer excite a resonance in that region. Is that the correct way to think about the solution?

Min Zhang:
Yeah. That's an interesting point, the way you interpreted. It might be true, I think. But the way I thought, at the time at least, was because the resonance structure has to be an ALC tank circuit to make it resonate. So the C really depends on the simple equation of any capacitance. Right? You've got the area of the PCB or the service and then you got the height and then you got the dielectric and you can sort of works out the capacitance of this structure. The L, and in this case I worked out, is the link, the leads or the legs of the PCB to between the two boards. So that, perhaps, gives about 10 nanohenry inductance in that case and then you can work out resident frequency in that case.

Min Zhang:
So when putting the ferrite, the way you interpret it is you basically push the frequency into a higher band. But the way I treated it, I think it's always important to remember that a ferrite is not a 100% inductive component. In fact, it is more resistive as a lossy component compared with the inductive component of a ferrite. So at the time, I thought it's because I used the lossy feature of a ferrite which is to add more resistive into this LC circuit to really dampen the resident frequency. So that's how I interpreted it. But the problem was solved by this application. But yeah. It's quite interesting to really see what is exactly the mechanism of this resonance. We really dampen it or is it we push the frequency to a higher frequency event.

Zach Peterson:
So I was thinking about this in terms of the wave propagation between the two portions of the system. So even if you have large PCDs and they're open at the edges, you can still excite a cavity mode. It's just that cavity mode could be very lossy and then by changing the geometry, you change the cavity resonance structure. But I guess if you're at lower frequencies, really, you could think of it then as a lump circuit, as you've said, like an LC circuit. And so, then what you've just said makes total sense. Right? You're adding in some loss into the system and then that would essentially decrease the Q factor of that LC tank circuit that you have unintentionally created through this daughter board configuration.

Zach Peterson:
But I guess if you look at it from a wave perspective, right, that ferrite is still a lossy material so you've also added in some loss. So I mean maybe it is both. I guess you would need direct measurements of the electric field or the magnetic field in that structure to really say which is the dominant mechanism of noise reduction.

Min Zhang:
Yeah. I think this is a really, really good discussion Zach because what we just did was actually trying to explain a phenomenon from both sides. So when I say both sides, we all know that lots of engineers are more comfortable with lumped circuit element analysis. So in which case they use ALC, perhaps with some resistance as a dumping element in their circuit design and often these engineers, probably, power electronics and guys whereas the way you see it, you treat it as a proper transmission line and that's the way lots of RF engineers and high-speed circuit designers think. I really appreciate it because as we just discussed it at the very beginning, I think understanding the first principle, understanding the basics is really, really important when it comes to EMI problem solving and CP design.

Min Zhang:
So I do encourage our listeners or our audience to really expand the view because I mean, RLC circuit design view is often adequate and it's simple, it's easy. But when it comes to high-speed design, you really need to understand how the wave propagates, as you mentioned. It depends on the number of the rounds of wave action inside your transmission line. Then you can really have the resonance reports on your voltage or current wavelength. So I think if you really understand the basics from both points of view, it will help a lot when it comes to EMC troubleshooting and also product designing.

Zach Peterson:
Yeah. That's funny that you bring up the RF thinking because a lot of stuff that I do is RF plus some high speed digital and I actually got into this from optics so literally everything is wave propagation. So I guess I kind of come by it naturally. But I think that's one of those areas where there could be some better education around it. I used to teach at a university and I think wave phenomena was always a little difficult for engineers. Most of my students were engineers and so, I was teaching physics. So, of course, we have to get into wave phenomena and I think that was one of the areas where it was a bit difficult because it requires so much visualization in your mind. You can't see, touch it all the time whereas with a lot of things that engineers do in a physics class, like in a lab, it really is tangible. The propagating waves creating resonances is not tangible and there's math that goes into it and I think that can be a bit daunting.

Zach Peterson:
Now you mentioned early, when we got started, that being at university, maybe there is more that the university structure of an engineering education could do to aid EMI/EMC education or training. Is wave propagation part of that? To what extent do you see wave propagation being part of that and maybe are there some other areas where the university system could maybe do better?

Min Zhang:
So I have to admit, when I was in my undergraduate degree, we had transmission line courses and to be honest, I didn't understand it and I didn't see the application of that. I think the biggest gap is you get taught a lot in a university but which of this knowledge is really linked to the real-life engineering? So if you're not using this knowledge, you quickly forget. That's just simple because we're all human beings. We forget if we don't practice especially, as you said, the wave propagation because it's just so abstract in a sense that we cannot see it. We cannot capture it but that's just the truth. This this nature.

Min Zhang:
We cannot see waves in the air although it's there. We cannot observe energy movement. The only tool we have is really the voltage meter and the current meter. But according to Maxwell's equations, we know that these are just the next layer below the Maxwell, the wave layer. So how to link these two layers is going to be a huge task and to explain it is difficult, to demonstrate it, and also how to link this to real-life engineering. I think that's going to be a huge challenge for university lecturers and professors, I guess.

Zach Peterson:
One criticism, or maybe not criticism, but one commentary I had just recently saw from someone on my LinkedIn that is related to this is test and measurement and that universities probably don't do enough with test and measurement. I'm going to admit when I was doing my undergrad and then later my graduate work, I didn't get enough exposure to test equipment until I started doing research and I had to jump in and learn it and break open the manual, read the theory of operation. You had to jump in the pool and learn to swim, as we say.

Min Zhang:
Yes.

Zach Peterson:
And it forces you to fail fast and learn from your mistakes quickly. And then, of course, there's a lot of hand-holding for the first couple of months where you're really learning to use some of this equipment at a deep level. Do you think universities should have just like, I don't know, a vector network analyzer course and an oscilloscope course? I think that would be interesting.

Min Zhang:
Yeah. Yeah. As we just said, having the course is one thing but how to link that to real-life engineering is another thing. I think a good demonstration would be, again, it depends on the funding of the university. If it's a well-funded university, you can always afford to buy a very, very expensive high-speed, I don't know, 10 gigahertz, 20 gigahertz oscilloscope. That would be a very good demonstration because if you look at, let's say, typical capacitor discharge, is it gives you the exponential curve. But with high-speed digital oscilloscope, you might be able to see the wave action we talked about and things like that to give students better understanding. And in fact, perhaps again, that's a good example of linking a simple RC circuit to transmission line circuit. Things like that, I think, would be quite demonstrative in a sense of educating the students.

Zach Peterson:
Well it's good to hear somebody kind of validate that because I've always believed that PCB designers should know something about test and measurement, at least which instruments somebody else should use to maybe diagnose the problem that they might have created on a circuit board. Even just knowing which measurements are important for which potential problems, I think, is really valuable. Even if you don't know all the ins and outs of that particular piece of equipment, you can at least point yourself or point a colleague in the right direction to then try and figure out some kind of solution to the problem.

Min Zhang:
Yes. So speaking of this point, do you happen to know anyone in say the United States or just in the world in general who's been quite active in terms of promoting testing skews or how to set up tests properly and things like that? The reason I ask is I know like back a few years ago, I think one of the people I admired a lot, even though I haven't met him personally yet, is Mr. Doug Smith. He's a very good EMI and ESD problem solver and I really like his book. I can't remember the name. It's High Speed Measurement or something. That's his only book published. I don't think you can buy the brand new book these days. You can buy them from the secondhand market and that book is really focusing on the test and measurements in terms of high-speed design, as you pointed out.

Min Zhang:
And also, there are other people in the analog world. I think one guy died a few years back and he basically wrote a book and I think it's an EDN series talking about how to troubleshoot on a circuit. These are very practical but if you really read into it, you learn a lot because everything's practical, I think. Yeah.

Zach Peterson:
There are three people I'm thinking of, two of whom have actually been guests this year on the podcast. So we had Eric Bogatin, who I'm sure you're familiar with.

Min Zhang:
Yeah. Of course.

Zach Peterson:
Heidi Barnes.

Min Zhang:
Yeah.

Zach Peterson:
And she and I were actually talking a lot of power integrity. But the third person I'm thinking of is Steve Sandler.

Min Zhang:
Yes. Yeah. I'm thinking of Steve Sandler. Yeah. Eric, I think he's everywhere because he just has such broad and in-depth knowledge. So I know Eric mainly because he's a CPE kind of expertise. Yeah. But I don't really think him as just focusing on the high-speed measurement side. But Steve Sandler, definitely. He is a typical guy in this field.

Zach Peterson:
Well Steve Sandler, if you're listening, we haven't had you on the podcast yet. So get at me on LinkedIn and we'll have you on to talk about this stuff.

Min Zhang:
Yeah.

Zach Peterson:
I think that'd be a lot of fun.

Min Zhang:
Yeah. Definitely.

Zach Peterson:
And then who did you mention? You cut out just briefly there but who was the person that you had mentioned?

Min Zhang:
Oh. So yeah. So it's Doug Smith and he wrote a book called High Speed Measurement. I will provide the book, maybe, so we can put the contents in the notes.

Zach Peterson:
Yeah. Yeah. We'll definitely link to that in the show notes so anybody who's listening can go and check out that book and if you send me a link, I'll probably buy it this afternoon.

Min Zhang:
Okay. Yeah.

Zach Peterson:
Well we're getting low on time here but this has been a really interesting discussion and I always love to talk about SIPI/EMI/EMC with other experts in the field. So this has been very illuminating and definitely valuable to look beyond just the PCB because even though your solution may be at the board level, the problem might not be.

Min Zhang:
Yeah. It's been a pleasure for me as well and I hope the conversation really has sparked some sparks within the engineering community and yeah. And beyond PCP, we have many, many interesting things to talk about. Yeah.

Zach Peterson:
Absolutely. Absolutely. Well thank you again so much. We've been talking with Min Zhang, independent EMC consultant based in the UK, and this has been very illuminating. Definitely would love to have you on again some time in the future.

Min Zhang:
Oh. That would be my pleasure. Yeah. Thank you very much. Yeah. Yeah. Thank you.

Zach Peterson:
And to everybody who's listening out there and watching on YouTube, make sure you subscribe to get access to all of the upcoming podcast episodes. Make sure to hit the like button. Make sure to leave a comment. If you have any questions, we can always take those on LinkedIn or we can take them in the comment section on YouTube and make sure to check out the show notes on the Altium website. There are going to be a lot of great links and we will make sure to, of course, link to that book that you mentioned because I always encourage people, go get a great book to read. Last but not least, everybody that's listening, don't stop learning, stay on track, and we'll see you for the next episode.