The Wireless Research Center

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Welcome to the macro fab engineering podcast where your guests Jerry Hayes and

Sruthi Sora.

And we are your hosts perkiomen and Steven Craig. This is episode 182. Dr. Hayes

has nearly three decades of experience in government and commercial electromagnetic research and design. Prior to establishing the wireless Research Center in 2010. Dr. Hayes work for Sony Ericsson mobile communications and Lockheed Martin. The scope of his experience encompasses electromagnetic theory, bio electromagnetics, antenna design, RF circuit analysis and material engineering. Gerard also has participated in the development of international standards for OTA, H, AC, and SAR evaluation, which includes IEEE IEC CTIA, and C 63. Standards. That's a hell of a lot of standards.

There's a lot of stuff.

So Froothie. Sora is a senior staff engineering consultant at the wireless Research Center. Through he has over 15 years of experience in RF and antenna engineering in the commercial defense and medical device markets and has developed products from early concept to production. Previously, she has held technical positions at RFMD, HTC, Sony, Ericsson and Harris.

So I'd like to thank you, Jared, and Sruthi, for coming up to the podcast. Thanks for having me.

Thanks for having us.

We've been we've been looking forward to this because there's a good handful of topics that applies to a lot of us electrical engineers that are kind of shrouded in mystery. And hopefully you guys can kind of distill that mystery for us.

Sure thing, we're excited to be here.

So before we get into that stuff, can you explain what the wireless Research Center is?

Sure, the wireless Research Center, we're a very unique organization, founded in 2010, as a nonprofit, 501 c three organ research organization, which keeps us neutral. Our mission is twofold. One is to advance communication technologies and promote economic development, what we've done is we've created a very safe space, that that provides a resource, a community resource, if you will, to people trying to advance wireless wireless connectivity, as well as startup companies promoting economic development, and fostering ideas. So we, we bridge everything from the Internet of Things, and on body and body types of connectivity, all the way up through air to ground and air to space. We provide access to engineering resources, the technical skills, as well as specialized testing capabilities. And then business development accelerator programs for startup companies wishing to go to market. So

it's it's interesting this year wireless Research Center is I kind of want to look at the 501 C three aspect of it. And I'm sure you get a lot of questions about that a nonprofit testing facility. How does that work?

It's testing is one portion of our capability. So it's it's it's a nonprofit, research and development organization. So the the nonprofit status allows us to be we're not owned by a particular business. So we're a community resource. We're governed by a board of directors. And we make our capabilities, our testing facilities, as well as our engineering resources available to all. So anybody from academia to industry, startups, small businesses, large businesses, government as well. We provide that technical resource, that technical feedback. We do. We do a lot of studies on next generation wireless technologies, as well as innovative products incorporating those technologies.

So you get a lot of academic work coming through.

We get a fair amount. We partner with several universities, we we allow the the researchers to use our test capabilities. We've got some very unique testing facilities. One of them is an anechoic, which means no echo shielded chamber It's about five meters cubed, which allows us to do radiated performance of antennas, or devices from 400 megahertz up to 18 gigahertz. So a very broad range of applications. And we make that available to academic researchers on a half hourly basis all the way up through startup companies as well. And we're accredited for those testing. So the accreditation means that our test reports are accepted, either from an antenna performance characterization or from an over the air OTA performance characterization for people like the sailor, telecommunications, industry and association of CTIA, or Verizon, and others.

Because I remember that being a big thing a couple of years ago, where the FCC was changing kind of the rules for accreditations for testing facilities.

So we, we've we've been accredited through a TLA, which is the American Association for Laboratory Accreditation. And that's, that's under the guidance, there's an ISO standard 1702, five. And over the years, we've been 1702, five accredited since our first inception of accreditation at the center. And we've maintained that and over the years, industry, FCC and other regulatory agencies have been pointing more and more towards that 1702. Five standard. What's, what's unique about about that standard, is that it combines a technical measurement procedure with a quality management system. So then, it's not only are you doing the test, according to the way you're doing it, are you doing the test correctly? With the right measurement, uncertainty, repeatability? And there's been a lot of focus to that to ensure kind of a repeatability globally? And that's an international standard.

Does that include methods on how to document everything?

It does, it does. That's that's what's called the quality system. So for an accredited test, it handles everything from your initial customer interaction, all the way up through preparation for the test, taking the data, processing the data, and then issuing a report. And all of that is standardized and harmonized.

Is there anything that goes all the way towards the to the customer as well as in your onboarding process? Is a a standard? Yes,

it is, it is. And one way to think about it is you want to make it fair, unbiased as well. And so it ensures that, you know, there's there's the integrity of the personnel, the integrity of the device. And it's, it's so that the customer can walk away with an assurance that they there's the data is valid to the best of the test testing.

So Stephens IoT toilet could be fairly tested.

That's correct. That's right. Yeah, I need I need a to a to LA. So I, we're sort of gotten off on the weeds on this. But do you get audited for that?

We do we do, we have to maintain the accreditation. And there are a series of internal audits every year and external audits every other year. And actually, the the accreditation covers, really, it's particularly to a scope. So it covers our over the air testing, as well as our antenna pattern and pattern testing. What it doesn't cover is that we do a lot of FCC pre certification work. And, and that is not a certified test are we don't have the right equipment to do that. But we do have the means to do a pretest. And are because we're neutral, or our forte here is that we provide a space where if you're if you wanted to do a pre test before you go to the compliance, you can run it here. And if there are issues, we can introduce you to engineering resources, that are very familiar with the problems and can provide very quick solutions. Or if you're at an accredited lab, and you know that you're failing a particular issue, you could come here and again we can prove we can repeat the measurement, provide the resources to help you get it to improve and to meet the requirements.

Our whole goal is to help see the customer succeed and see their product go to market. So we try to be able to provide as many resources as possible to be able to help them get to the point of passing certification as fast as possible.

And as you can imagine the application of radios to IoT devices, it's just exponential. Right? So not everybody has an antenna, RF engineering staff. So that's where we're that shared resource to help you get through that.

Can we? Because I have a lot of engineers that always asked me about FCC pre certification? What is involved in that?

Yeah, so FCC pre certification. The main thing with that is running a test, like Jerry said, it's not certified, but it's good for development testing. And what that does is give you a warm fuzzy, whether you're going to pass certification, are you going to be marginal, or are you failing? So things that are checked are RSC radiated spurious emissions, all and what that's trying to check is making sure that your device is playing well with others that it's not transmitting outside its frequency band, beyond the limits that the FCC or regulatory bodies indicate. So those are things that, you know, you have to have your full system, we can turn it on, run it through that test. And if you're not using a pre certified module, there are some tests that the radio would you would check for to make sure that it's staying within the boundaries of the power limits, and the waveform shapes and such. And those are all good things to check prior to official certification. Because if you fail official certification, you need to start all of that, again, after you get to the point of debugging and optimizing. So we try to help people through that process.

So how do people get started with that, at least with you? Do they just like call you up, or they just show up at your doorstep with a box? What expectations does someone have?

Yeah, we usually prefer a call or an email just to schedule the time. But, but usually they'll they'll come to us, we'll work on an NDA, we keep all company information confidential. And then we'll we'll talk to them about their goals for the product, how it's being used, and then figure out the best way of precheck testing, whether it's on the regulatory side, or even the OTA side. And even help out with design reviews, if they are early in their project to get as many design hooks in place early on. So it can save them time and money later. So we usually come up with a set of tasks that we can help them with and just work through them through through those with them. As the project progresses, we usually prefer if you get involved if if we get involved, when it's just an idea, even prior to your first prototype, because there are a lot of things that you can do, even before building that first set of hardware, to be able to kind of determine the feasibility and what areas need to be changed even prior to building that first set of hardware. And once that, that first prototype is available, then we can run pre checks, optimize and go through the different steps.

That's great. So So I guess, I don't know if customer is the right word, but your customers can can reach out to you and get design resources before even doing the pre certifications. Right?

Exactly. Yes. Yeah. Our expertise, especially, is in antennas and RF, but what we can do is look at the layouts before they're actually built. There are a lot of off the shelf antennas out there. And we can help people navigate and figure out which one's the best for their application. You know, whether it's a wearable device or something mounted on top of a vehicle or you know, inside a building, and help walk through that. And one is we can simulate the others, we can actually build what we call a mock up, which is a hand built prototype without you know, PCB boards, and actually throw it in our chamber and get you know, quantifiable results, even before the software is even ready.

That's really cool. So So when it comes down to it, I'm curious about the simulation. When you say simulation, are you simulating some kind of a 3d model? Are you actually simulating the actual board itself?

It's both actually, we would get the mechanical model or we can draw, you know, aspects of it ourselves. And we would actually look at it from a 3d perspective of you know, what components are close by, you know, should the battery be one, two or five millimeters away from the antenna and run those parametric sweeps and those are really important to think about at the beginning stage because once your mechanics or the cosmetics are fixed, it's hard to move things around. So simulations really come into play where you can kind of adjust and move and shuffle things and try to get the best system solution from from the intent and radio perspective, but also from the mechanics and the hardware, and the all the other players involved in the whole system.

Yeah, the tools are strong enough that we can import a full mechanical CAD model as well. And then import that in. And that's one of the the leaps that the technology has taken in the 90s. And early 2000s, is being able to simulate things as complicated as a sailor handset with all of the different components inside of it as well. And it

allows you to visualize things that we can't actually see with our eyes like the way the surface currents go flow, and even just the antenna pattern prior to it being built.

And all of those things impact the radiated and antenna performance.

Yeah, so for an IoT product, what you really want to make sure is that you're able to, you know, for that device or product to be able to transmit that data. So to maintain a good antenna and radio quality and hold a connection is really important. So that that's what we're trying to guarantee.

So just out of curiosity, how often do you get products where the antenna isn't designed by the by the engineers, how often do you get products, where it's like some module that they just plopped down on their board somewhere and said, let's give this a try,

we get that a fair amount, where they'll they'll think they'll buy it like right off the shelf, and put it down on a layout, that's kind of the recommended layout that's in the catalog. That challenges that things around it like the PCB size, as well as anything metal has an impact. But as Sruthi mentioned, we're very good at helping to re optimize and maybe find the right antenna solution for that. Fewer and fewer people or a lot of people are have an appreciation for the antenna, it's no longer thought of kind of just a drop in replacement for many applications.

And the key part, there are a lot of off the shelf antenna options out there. But we can help people decide, you know, is it good to just go with an off the shelf or is a custom you know, when needed, but if an off the shelf one, you know, you might have antenna a and it may not be the best for all applications, you know, antenna beam might be the best for you know, for a vehicle application. And you may not use the same thing for like a risk device. So we kind of look at the whole structure and the whole system, and also understand what the use case scenario is and help come up with the best solution for for that product. And with the chambers, we can actually try it out and actually quantify and actually make measurements to be able to say, you know, this is the best for for your application.

Because I'm going to guess that a risk device only has you know, in the worst case scenario is it has a transmit through someone's wrist. Whereas an a car, it might have to travel through the entire metal structure of the body.

Yes, there's there's there's challenges for both by the on the on the as you mentioned with the body effects, if the antenna is pointed towards the body, you know, it can radiate into the body, which is lossy, which will affect its radiated performance. And similarly with a vehicle inside of a vehicle. There's some issues with with performance going through the glass and on the outside. And then depending on the frequency, you'll have problems or challenges with where to mount the antenna to be more optimal.

Yeah, and what's something that's foreign on the wrist, your hands always moving around. So the type of metric that you use to be able to, to specify what antenna is best is going to be different from something that's mounted on a vehicle that's always, you know, mounted in the same orientation. So we kind of help help them figure out what's the best metric to look out for their application as well.

So you're not going to put a human in the chamber with a with a watch on and have them wiggle it around while you beam them right.

So actually we are chamber. It's a it's a very large, it's an MVG SG 64 NVGs, the microwave vision group. We can handle anything six feet and smaller. And we do have the ability to put a human in the middle and sit on a chair. So that imagine if you are a first responder, a warfighter or a medical device where you have a lot of personal body electronics, we can put you in the chamber, and we can measure that radiated performance. It's very cool. We also have an agreement or an arrangement with the itas which is Foundation, which is a nonprofit research group in Zurich, Switzerland that build human body motum models both numerical simulation is real as phantoms. And so together with them, we have one of their full body phantoms that we can put a wristwatch on, or an external pacemaker and put them in the chamber to see the radiated performance. So it is, it is pretty, you're not too far off there.

I'm imagining what the thing looks like. And I'm like, you know, a Mythbusters, where they used to make like their gelatin people imagining like a horror show. You see the bones and stuff underneath it?

Yeah, the a lot of a lot of electronic data sheets have the human body model when it comes to ESD written on there, so somebody has to make that right. Somebody has

a lot of science behind them, actually. So it's a over a different frequencies, the body has a different different reaction. And those guys in Switzerland take all of that into consideration.

For sure. So I think Parker was kind of getting on this earlier, and we went a little bit down a path, but But it's okay, so let's go. Let's look back at the FCC pre certification and say, Okay, let's say I'm a guy who I've got a I've got a widget or gizmo now and I want to get it pre certified. What would I need to bring? What would I need to expect on the day that I show up?

Sure. So for pre certification on the the regulatory FEC SEC side, we would need hardware that's actually functional, that you know, the software and the firmware, and you've got the whole mechanical structure. So we're looking for the whole system to be functional. And we need the ability to be able to have it transmit at different channels and frequencies and max power. And so what we'll do is before, you know, you come out, we'll go through a checklist of making sure that you have all the pieces. And then after that, you know, what we'll ask is, I guess before that, it will also ask what frequencies you're planning to operate in, if it's cellular, or Bluetooth, or Laura, or no RFID, whatever it might be, and then make sure that we plan, we set up the test plan accordingly. And so we'll probably have a lot of initial questions just to make sure we understand your device and what's inside it. You know, is it battery powered? Or is it plugged into the wall or whatever it might be, and then go from there. And then when you come in for testing aren't you know, it should be as soon as possible. If all the software works as expected, then you can just go you know, one test after another and get a lot of data, even in the span of half a day to a full day.

Grid. And then so so with with devices that are plugged into the wall, how do you handle those?

So we have outlets that are, you know, clean power sources. And so we would plug that in into that source. And so we're really purely looking at the device and not, you know, external noise sources that can get in.

So what if my device is not intended to radiate anything? What if I'm just trying to check noise levels? Will you do that also?

Yeah, we can do something called idle mode testing. So basically, you turn the radios off. And that's another thing that we do check and making sure that, you know, all the other pieces of the entire system are still following the FCC FCC regulatory requirements. So when you have you do two types of tests with the radio off just looking at it, like as it is, and then turn the radio on, and then seeing how you know, are there any things that are mixing together interfering? So the key part is to look at the whole system? You know, the plastics, the the wires, the way it's hooked up at everything? But, but yeah, it's important to look at both.

So I've got a question for, let's say, these people, before they even get to you, or they can't get like let's say they live in like, Hawaii. Getting to y'all in North Carolina would be a little hard. What recommendations would you have for a startup starting out? Over there?

Actually, we've got customers all over the globe. And we, we start off with if they're, if they're that far away, we'll start off with a teleconference and then do a video conference. We can even do the design review remotely. And we've had customers especially on the West Coast, ship their prototypes overnight, and then we'll have them tested. When and with the results. That's that's the beauty of the center is we're able to analyze the results as well and to kind of give them feedback almost in real time.

Yeah, so you don't actually have to be physically here. You can you can mail your device to us, and then we can test it and then, you know, talk over and go over the results together, you know, over the phone,

and many of those we've already done simulations for them. So we're familiar with the device, at least conceptually and on model size. Gotcha.

So, in my experience with doing things like CEE testing, I always showed up with a backpack full of, you know, soldering irons, ferrite beads, extra resistors, capacitors, things that I can throw the device in the chamber, test it, if I need to change something or change it, do it again, do you allow for that?

We do, we do. And we have, either you can come in with your own kit, or we have kits here in the lab as well. And we also have the engineering resources, there are a couple of for profit engineering firms in our commercialization center, that we if it got too complicated, we would hand you off to those guys as well. And they've got the soldering irons, workstations and an engineering personnel to really take you through the finish line there.

Yeah, one thing that's really different and unique about the center's we have all sorts of equipment that we make available for people to use. So you know, you don't have to have your own soldering machine or RF test equipment or whatever you can, you know, rent out ours. So then, you know, people don't have to spend millions of dollars on a chamber, they can just use it for several hours here and have access to the same type of, you know, feature, you know, technologies and such.

So do you get a, like, if you were to come do testing, do you get a tech that kind of works with you for the day.

So we have, we have the technical staff, the engineering and the technicians. So our our hourly rates that we charge include the technician services, that actually the end of clarify, those technicians are there to operate the chamber to take the measurements, we do also have technician and engineering resources, if you need them, in addition to doing like the design modifications on the board,

swap in for at beads, capacitors around stuff like that,

if Yep, and we have sample kits of all of this. So if the right ones not in your bag, you know, we will we'll have a whole set of different ones to choose from to to make sure that we can optimize it to the best.

One of the things I really found helpful was doing a wide frequency sweep on my products, finding where everything was was awful. And then just zeroing in on that, because it's been my experience that the long frequency test took forever to do, we would show up in the morning, do a baseline test, find our bad areas, and then zero in and focus on those and just try to fix those and then go back and do a long test. And that always seem to work really well for me.

Yeah, I mean, that's a good approach. And one thing that we would recommend is even prior to the test, you know, through a design review, we could actually look through the schematic and the layout to be able to determine a potential sources for for those certain frequencies. And then if we can get in at the early concept actually put in design hooks and placeholders for ferrite beads or filters or things like that. So then when you come in, we're like, Okay, well, we just populate or no populate certain components and all the hooks are there. But yeah, it's definitely good to start off with a good overall sweep, just so you can figure out you know, where this, you know, the the frequency peaks are and then start figuring out, you know, what could those be caused by?

So I guess, could we get a little more technical on the engineering side for designs? Sure. And like the capacitors and Vera beads, so like, where would an engineer replacing, I mean, like, you can put ferrite beads and capacitor like let's say, oh, six or three packages all over the board. But without strategically putting them in the right spot in the right signals, they won't do anything, right.

So that's kind of where the the, if we do a design review ahead of time, will will will give you recommendations of where to place like the matching networks, you know, you could think of like a pie network or at the feed point of an antenna. Or if you want it to match if you got more complex antenna designs, where you have maybe parasitic components, you can put inductors and capacitors to kind of match that impedance as well. Simulations will help with that. The ferrite beads from an RF standpoint, the ferrite beads you want to be you don't really want to put them in in your feed line, you know, because they tend to lose be lossy, right. But, but in terms of mitigation of spurious um, that's where it kind of becomes kind of an art of people that have done it before kind of have an idea of where is a good place to connect the ferrite bead or that or to connect the ground?

Yeah, I mean, one thing that we look at our Are all the layers of the layout because it could be, you know, something on the opposite side of the board that's, you know, mixing together, and then getting back in into the RF trace, and then it turns into a frequency that you don't want. So we're not putting ferrites everywhere, but we're putting them in strategic locations by looking at, you know, the overall system, you know, and proximity to different components, different subsystems like power supplies, batteries, things of that sort, as well as like the the radio module itself and making sure that at the early stage, each layer is what it should be expected to be. And if it's not, when we're testing it, we can make modifications, even with just soldering components, or even making exacto knife modifications. Or, you know, even making having a second prototype if it's a deeper dive.

So yeah, I got a question on, let's say you're doing a full on FCC compliance test, and you do make a modification to your board? is, do you just have to roll that into your next revision that goes into production? Or do you have to come back with a fixed board that was made basically, and get that retested?

It really depends on the the FCC. So what the good thing is, we're doing an FCC compliant testing. But for the actual testing, your device needs to be indicative indicative of what you would expect in production, right? So if you made a modification, and you have a reasonable expectation that that's what it would be in production.

Yeah, and another thing that I mean, what we recommend is, as you get to different prototype revisions, and you get closer to the final version, you know, we start testing more samples and things like that to starting to look at, you know, not just one, but you know, let's say five or 10, and kind of a subset. So then when you're ready for official certification, then, you know, you know what the whole product as a whole how it would respond. So one thing that we also do is work with the customers to make sure that, you know, we're testing in our chambers, but also adding tests potentially, to their manufacturing line to make sure that your device is in a consistent over a large sample.

Yeah, I'm gonna guess that helps solve like, tolerance backups. Yeah. Stuff like that. Yeah.

So what's the what's the deliverable that you provide to people at the end of testing? Do they just get a chart that says, Yay, or nay? Or do you actually get plots of how everything goes?

The sheet of paper that says, okay?

Yeah, we usually provide a test report. And so whether it's if it's different development testing, for accredited testing on the OTA side, it's it's more formal,

and there's a specific certified test report for the certified

testing. But yeah, usually for pre check, whether it's on the FCC side, or even the OTA side. Usually, they'll be plots, there'll be numbers or tables. And then even more, most of the time, we'll try to go over those results to make sure that you know, they understand and they're interpreting it in the right way.

Got it. Got it. And so it's pretty easy to interpret from that if you pass or fail, right? Yeah. Yeah. Parker, you want to you want to talk about USB shielding?

Yeah. So this is a question. We brought up a couple of different times on the podcast. And the USB. I have one of them was this center USB group. I can't remember what the actual conglomerate of people who've run that standard is. They have, they don't really have a recommendation of how you connect the shield to the ground of your PCB. It just it basically just says do the best practice that works the best. Basically, what boils down to how do y'all wreck if you'll have a recommendation for engineers how to connect a shield to ground from an external source like a USB cable?

So So our recommendation is, is typically to have as much ground around there as you can much ground plane grounded area with vias connecting all of the ground planes. The thing that you want to avoid is having areas that may have a different electrical potential. And some people not familiar with RF might make that mistake and think oh, I have just a trace underneath my USB and that would be sufficient for creating a ground on And the reality is if you follow that path length back to like another larger area, at RF things have wavelengths. So what's grounded in one place may not necessarily be ground somewhere else. And those are things that we, when you simulate it, you can actually see very well, where the current hotspots are, then you can see where things break down. Fortunately, there are there are most RF engineers, there is some learned, good engineering practices that that people make to have a decent ground. Again, if it's floating that swing, especially when you get like high speed data through USB, there's potential for currents to flow if the grounds aren't well connected.

Yeah, and it really just depends on the specific application, if you have a lot of real estate, there's a little bit more that you can do. But if you have a really small amount of space, you just take, you know, paying attention to some particular areas, like Jerry mentioned, the vias or the just the dimensions of the ground plane can do a lot.

Okay, so that brings up that brings up a question, we've talked about a whole bunch on this podcast. And that's, that's grounding. And I'd love to talk about real quick grounding in relation to passing these kinds of tests. And so you know, just a general favorite that seems to run around here is what we call plane and plunge, where you have at somewhere on your board, you have an unbroken ground plane, and anything that's on the opposite side of the board, travels to that ground plane through a via that's close to whatever pin. And that's really, it's really simple to accomplish. But are there a lot of merits to that? Or do you would you modify that? What What are your suggestions on that?

I think I mean, as far as you know, have, we always recommend as far as grounding, at least, we look at it more from the RF and antenna perspective. So kind of like Jerry said, we're looking at it in terms of wavelengths parasitics, you know, each each trace has an inductance, and capacitance. So we always recommend, you know, multiple grounds, depending on the wavelength of operation, then, you know, the intensity of grounding will change. But it really, it depends on, you know, the location and kind of the antenna. So it's not kind of a one size fits all type of answer, it really depends on on the board and, you know, putting a ground and let's say, it could be potentially a noisy crowd, if it's, you know, hooked up to a power supply or something, grounding in that spot may not be the best. So it's really looking at how does the power plane and the grounds and the RF all play together along with the baseband hardware as well. So I guess there's, there's no one right answer, it's just really, it tends to with design guidelines and best practice, and that specific application,

and that's where a design review really pays off. Because when, you know, if somebody may see is just an area without enough vias, an RF engineer might say that that's a perfect capacitor that you're building into the system type of deal.

Right? How about the the argument that I've heard a bunch of times about splitting your analog and your digital grounds? Do you recommend that more often than not? Or do you recommend against that?

Yeah, I mean, it's good to keep certain aspects separate. But it's also you know, if you, if you split it up, you don't want to just make it like, the RF ground is just half the board, you still have to tie them at some point,

if the answer there, it starts to depend, right. And it depends on your interconnects between the analog and digital and more and more that it's becoming more difficult to separate those sides as well. Especially if you have a direct converter, you know, from you know, analog down to DC. And then that's when it's really important to pay attention to your grounding.

So Parker, you You recently had some interesting ground plane stuff that you were working on, right?

Yeah, so I was working on the Pinball Controller and I mean, this is a system that you've got five volts 12 volts 3.3 volts and then a 50 volt you know, high current high impulse from solenoids, you know, firing off. So, I usually on that one, I kept all the 50 volt stuff separate or separated completely, and they only connect through a little tiny jumper across the ground planes just to make sure you know, the ground potentials are are the same, but that's actually you'd like to think about, it's actually two separate digital planes there. Because the MOSFETs are in full saturation, you know, in theory all the time, right?

And if you're switching high currents, right, so that's, that's going to create very large impulses. And if they hit any non linearity, they're going to generate harmonics as well. Exactly.

I guarantee they're hitting a bunch of nonlinear, yes.

And then like the, on the five volts, like the five volt line, we're pulling seven amps on that guy. And that gets put down to 3.3 volts. So the three per volt three, which is running all the digital logic, that's only pulling like 100 milliamps. And the rest of that is running lights, which of course, you can flash them on and off. So you got you can have up like six amps going off and on, you know, at, you know, 200 hertz or plus. And so I made sure basically on those, Steven that made sure those ground returns are separated out. So like the 3.3 volt line returns a different way than that high current five volt line does. Just try to keep it away and separate it out. So it doesn't all go down to one ginormous plane. All the 3.3 volt stuff does, but the high current five volt stuff, I routed its own return path.

Sec, you paid attention to the current flow, right. Yeah. And that's what we do at the RF side as well.

Yeah, I think I think that's an excellent example of where the one plane doesn't fit at all. kind of situation. If you're all playing in in the same general realm of speeds and currents, then maybe it does. Right.

Right. Right. That's right. That would be an example where you would want to keep it separate. Yeah. Because one plane is noisier than the other as well. Right? Exactly.

So out of curiosity, I mean, we've, we've talked a lot about FCC pre testing. And, and I think a lot of that is due to the fact that on our side, we're really interested in that. And we get a lot of questions about that from our listeners. But what other kinds of testing Do you offer?

So we do antenna testing, like we talked about the OTA testing. So that looks at how well a device transmits and receives when it's in a full system with software and everything. But even prior to that, we can do what we call antenna passive measurements, so we can see what the antenna pattern is in that mechanical structure, even prior to working hardware. So we can either you know, hand build a prototype, or you know, utilize a first revision, but that says the antenna pattern is pointing in this direction, or, you know, it's pointing in all directions. And we can use, you know, the body phantoms and such, we can also do field testing, we actually have portable towers, available for rent as well. So people can go out into the field, and actually, you know, look at how you know, how much loss is, you know, through trees or you know, going to talk to something, you know, far away or tower to vehicle or whatever we do, you know, all of the LTE cat and one narrowband IoT types of protocols. And then if it's outside that what we do, if it's like a Bluetooth or Wi Fi, or Laura, or an ITSM, man, what we do is have the device transmit a constant CW tone, and then in its full mechanical structure, we can actually measure what the antenna pattern is for that. So where that comes in is, is one thing that we recommend thinking about, are there three types of tests, there's the regulatory side, which we talked about the FCC compliance, there's the over the air OTA side, which, you know, if you're trying to get on a carrier network, you know, there, there'll be certain specs to that. And then the last one is what we call use case testing. So making sure that your customers happy as well. And so with that is making sure that the device is tested in a, in a use case, applicable environment, like, like, like the pinball thing that you were talking about making sure that, you know, it's tested in an environment that looks close to what how it will be installed, and making sure that the performance is, you know, to the best of our ability there. Because, you know, you could pass all the regulatory stuff, but if your customer you picks it up and they're unhappy, you want to make sure that you know, they don't return it as well. So and then,

and then we do it any other kind of custom eyes test for the application. So we're pretty flexible and adaptable for that.

Yeah, we have multiple chambers at the facility. So yeah, we set up custom tests are Are you used the standard says, Well,

I kind of see envision going to the local bar that has a pinball machine and bringing in all these tests, antenna equipment, just pinball machine works.

Assuming you got any other questions,

you know, I do, there's, there's one other quick thing that I believe could be useful. And I don't know exactly how, how this all works out. But if somebody was wanting to use your service for let's say, half a day or a full day, is there a way that they can estimate the cost, in terms of, you know, trying to do SEC testing?

Sure, the easiest way is the is to go to our website. That's a www dot wireless center hyphen NC dot o RG. And, and there, we have a request for test form. What we find are a lot of people will either underestimate the length of time or severely overestimate the length of time. And so what we do there is we get an inquiry, and then we'll we'll engage the discussion with what's the what is the device, how many frequencies because some some of the tests, we can do antenna pattern measurements, we can do multiple frequencies in less than two minutes. For full 360. Spherical coverage, you know, others take a little longer, like up to 40 minutes per test. So it kind of depends. And then we have hourly rates for our engineers and for our test facilities. Great, yeah.

Cuz just earlier this week, in our Slack channel, we actually I had a couple of questions where people were like, I've got a product and I want to get it certified. How much is this gonna cost me? And we're sitting here like, well, you know, get ready. Yeah, but But you know, it's kind of hard to tell you an exact number. So it's nice to be able to have some kind of a resource that at least gives you an idea.

Right, right. Yeah. And our recommendation is, always pre check and start early. Because it might, you'll, you'll spend a small number of dollar signs up front, but that will save you money overall. Because if you go to testing and you end up failing, then then you have to, you've already got your product developed. And then you have to make some major changes to either the tooling or PCB, or whatever it might be. So we always recommend, just pre check and get to, you know, start start asking those questions early on. And if if we can't do that, that specific test, we can point you in the direction of people who can?

Well, excellent, what is a good way for our listeners to get in contact with you?

Sure, like Jerry said, if you go to our website, and then there's an info at wireless center, nc.or o RG or there's a Contact Us form. So send us a note. And then and then we'll we'll reach out to you and then usually just start off with a either a phone call or a tour. And if you're ever in the North Carolina area, shoot us a message and we'd love to have people come and visit and you can actually see the chambers and stuff upfront in person because they are pretty cool.

They're also acoustically quiet. So you get to really see how quiet the chambers can be.

So that was about to ask that because you said you put human beings in to these things. One gone insane from just like the lack of noise.

We haven't had any certified insanity cases.

Well, you guys aren't certified to test for that yet. That's correct. That's correct.

And I've got another question if y'all can say, cuz I know you like sign NDAs and stuff with people, but like, what is some of the craziest things that ever come through your door to be tested?

You're right, most of most of the craziest things we've seen are very much under our NDA. You know, as you can imagine, you know, everything, like especially body worn types of applications, up to small aircraft parts as well.

We cover a lot of different frequencies, all the way from super tiny all the way to super large. So we and in our expertise, each of the the folks on the engineering staff have different specialties so we can cover a lot but Yeah, unfortunately, everything's under

it's never a dull moment.

wasn't you who had went to one of the testing centers and there was a bucket of like, cow analog. Was that you was that church? Cow? Annaleigh Wait, what?

Yeah, I

can't remember his phone was testing the a device that a cow would swallow into they had to simulate the environment that would be in which was a bucket full of

Oh, I get a cow analog gizzards in a bucket, right? Yes. That was not me.

That was purchased then

we we've tested things with different things simulating human body parts.

It's always exciting.

Yeah, you have to go to the butcher and be like, you don't want to know what this is for. All right, fantastic. Well, thanks a lot for coming on. We really appreciate it.

Thank you so much, guys. Thanks.

Thanks for having us. And you know, thank you. And you know, that was the macro FEV engineering podcast, and we were your guests, Jerry Hayes and Shirky

Sora

and we were your host, Parker, Dolman.

And Steven Craig. Later, everyone, take it easy. Bye. Bye. Bye.

Thank you. Yes, you our listener for downloading our show. If you have a cool idea, project or topic. Let Stephen and I know Tweet us at McWrap at Longhorn engineer or at analog E and G or email us at podcasts at Mack fab.com. Also, check out our Slack channel. If you're not subscribed to the podcast yet, click that subscribe button. That way you get the latest episode right when it releases and please review us wherever you listen, as it helps the show stay visible and helps new listeners find us