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Go to Technology Today Magazine Podcast Episode 61: SwRI’s 2023 R&D 100 Winner

Episode 61: SwRI’s 2023 R&D 100 Winner

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R&D World Magazine named SwRI’s Wideband Conformal Continuous-Slot Antenna Array a top 100 innovation of 2023, recognizing it as a world-changing, revolutionary technology. The high-performance, high-frequency, direction finding and signal acquisition antenna for naval ships is a compact, powerful new tool enhancing national security and public safety. Hear why the location of this innovative antenna, where it is positioned on a ship’s mast, is also an advantage.

Listen now as SwRI Engineer Patrick Siemsen discusses the award-winning antenna and the 1948 theory that served as the inspiration behind its unique design.

Visit Signals Intelligence Solutions to learn more about SwRI’s signal acquisition capabilities.


Below is a transcript of the episode, modified for clarity.

Lisa Peña (LP): We have a winner. And SwRI Technology has won a 2023 R&D 100 Award. The honor is known as the "Oscar of Invention" and goes to the most significant innovations of the year. We'll tell you about the groundbreaking Naval ship antenna that's starting to make waves on the high seas.


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Hello, and welcome to Technology Today. I'm Lisa Peña.The R&D 100 Award, presented by R&D World Magazine recognizes the 100 most significant innovations of the year. SwRI has won 52 R&D 100 Awards since 1971. The award goes to disruptors that will change industries and make the world a better place. Our guest today is SwRI engineer Patrick Siemsen. His team developed a disruptive antenna technology for Naval ships. He's here to tell us why the antenna is a game changer, and its role in national security and public safety. Also, it's the podcasts five-year anniversary. We've been discussing world-changing technology, science, and engineering since November 2018. This innovative antenna is a great topic for this milestone episode. Thanks for joining us, Patrick. And congratulations on the R&D 100 award.

SwRI’s Wideband Conformal Continuous-Slot Antenna Array

SwRI’s Wideband Conformal Continuous-Slot Antenna Array, a high-performance, high-frequency, direction-finding naval ship antenna technology, has received a 2023 R&D 100 Award presented by R&D World Magazine. The antenna, part of SwRI’s AS-750 family of advanced antenna arrays, is overcoming limitations of traditional shipboard antenna elements and supporting signal intelligence systems operating in the ultra-high frequency (UHF) and super-high frequency (SHF) bands.

Patrick Siemsen (PS): Yeah. Well, hi. Thanks for having me.

LP: So we want to get right to talking about this game-changing, groundbreaking antenna. It's called the Wideband Conformal Continuous-Slot Antenna Array-- a really long title-- and we'll talk about what it all means in a moment. But first, let's discuss the award-winning antenna's applications. What is it used for?

PS: Well, first and foremost, what is it used for? It is an antenna, so it is used as a listening device. But more importantly, in this case, it's a direction-finding antenna, meaning it's used to determine the direction of rival, incoming radio waves. Search and Rescue may be the first that comes to mind. This is probably, the primary mission of Coast Guard, find someone in distress. So if that person can turn on a beacon, the Coast Guard can go hunt it down. They see the signal come up on their system, they follow the direction it's telling it's coming from, and bam, you have them. For communications or intelligence purposes, you're only paying attention to unknown signals or at least, signals that are uncooperative. So you won't know where they're coming from, and that's the whole purpose of direction finding.

LP: A lot of important uses here. You mentioned finding the direction of incoming radio waves, search and rescue, intelligence uses, so walk us through step-by-step how the antenna supports operations in, let's say, a search and rescue scenario. It collects these signals. What happens next?

PS: Well, of course, it's connected to the processing equipment. Usually, a bank computers that process the information from the antenna. Now, it usually displays what's called an RF spectrum, showing all the signals across frequency. And the user will analyze this. The first thing that has to happen is determining the direction of the signal or/and the signals any interest to the operator. There are no rules in determining this, just depending on what you're looking for. It could be type of modulation. It could be a voice. A certain language of the voice. It could be the power level. IT could be even the direction it's coming from. Then, you act upon it appropriately.

LP: So you're talking about a lot of signals here to sort through. How many are we talking about?

PS: That's typically, why there's a lot of process equipment to just, do all this sort of processing automatically.

LP: Hundreds, thousands of signals.

PS: Correct.

LP: Yeah. OK.

PS: Under the hood.

LP: All right. So a lot of equipment backing up the antenna. And eventually, you find a signal of interest. And that's where you-- that's where you follow, or that gives you the information you need to go--

PS: Correct.

LP: --where you need to get. OK. And when you're using it for, let's say, intelligence purposes, that's a little different?

PS: Yes. Yes. Intelligence purposes, which is why you need a wideband antenna, they're uncooperative. They could be anywhere in the spectrum. In fact, if they knew you had the ability to listen in one area, they're going to deliberately transmit in a different area if they could. So that's the purpose of a wideband array. Search and rescue might be a little different in that there's channels that they frequently know, if you're in distress, you transmit at these frequencies. That way, the Coast Guard or whoever it is can easily pick you up.

LP: Certainly, many uses for this award-winning antenna. We want to talk more about the title. So every word in the title refers to an important antenna element or characteristic, Wideband Conformal Continuous-Slot Antenna Array. So what does the title mean?

PS: There could be more, actually. So we're just trying to capture some of the important features here when we came up with this title. Wideband, and kind of like I mentioned previously, just because it covers a wide, in this case, multiple octaves of frequency range versus saying just having one narrow frequency or channel you can listen to. See, conformal, that the antenna elements do not protrude much out from the mast. This helps for vibration and shock reasons. If it's an airborne application, then it would have lower wind resistance. Things like that.
Portrait of Patrick Siemsen

SwRI Engineer Patrick Siemsen led the development of the Wideband Conformal Continuous-Slot Antenna Array. The antenna’s unique design was inspired by a 1948 theory by Harold Wheeler, a 20th century electrical engineer and inventor.

LP: So it conforms around the mast.

PS: Correct. Correct. And then, finally, continuous-slot, first of all, it is a slot element technology, so the typical slot array. It's a complement to the dipole array. I do say, continuous-slot here because the array wraps around the mast and comes back on itself, much like a belt would do.

LP: Great visual there. And we'll have pictures of this antenna on the Episode 61 web page so listeners can see exactly what you're talking about when we say it conforms around the mast, just like a belt. This technology is disruptive. It is groundbreaking. It won this important award because of its game-changing features. And there's a really interesting story behind the antenna's design. So your team was inspired by a 1948 theory by Harold Wheeler, a 20th century electrical engineer and inventor. So tell us about the antenna's connection to Wheeler.

PS: So Wheeler is credited with coming up with what's called the current sheet concept, which basically is an infinite two-dimensional array, very small and very close dipoles arranged in a two dimensional matrix, if you will. The theory is that in such an arrangement, the dipoles complement each other and behave constructively in such a way that on the lower frequency side, they perform well and constant all the way DC. Of course--

LP: Can you explain that, "they perform well and constant all the way to DC."

PS: Yeah. DC is zero frequency, if you will.


PS: Of course, that's theoretical because the antenna has to be infinite, in this case, two dimensionally infinite, and you can't have that. On the other frequency side, they perform all the way up to what's called the Nyquist spacing, which is the spacing of half the wavelength of the radio wave. DSP designers will be familiar with this term. Nyquist is used a lot there. One thing to note is, it's an inverse relationship between frequency and antenna spacing. For traditional elements, they are designed by themselves, meaning there's nothing around it, just the antenna itself. But when you bring another antenna near it, it could be an identical antenna, but it affects its behavior. This is called mutual coupling, and it has a degrading effect.

Well, Wheeler's array didn't have this. They are all designed together. And this is where the numerical modeling tools we have to take come into play. That's what's different or disruptive about this new technology, or the new way of designing antennas. Wheeler didn't have this advantage during his day. Now, of course, practically speaking, for Wheeler's array, there is no way to feed or combine all these infinite elements together. You need some sort of physical structure to bring them all together. So really, it becomes a trade-off between what's practically realizable and performance.

LP: So you're really delving into Wheeler's theory here.

PS: Yes, we are.

LP: And then, you found a way that-- it was the base of what you were envisioning--

PS: Correct.

LP: --but you really helped-- you really made it better.

PS: It comes down to, how are you going to realize such an array? Again, it's an infinite number in theory, and there's just no way to realize that. And so, it's coming up with that practical realization of the theory.

LP: What do we have now, in 2023, that Wheeler did not have? I'm sure there's a lot. But in back in 1948, what were his limitations?

PS: The numerical computing power, of course. And in an infinite array, it's just more math to do. More computations have to be made. I don't know how he did it in his days without anything, but he did it.

LP: So now, we have the processing power to bring it to life--

PS: That is correct.

LP: --to bring his theory to life. And you not only used his theory as inspiration, but of course, you built on it. So this antenna stands out for a few reasons. One, it's compact, only 7 inches high, but it's interesting that the location where this antenna can be installed is one of its advantages. Explain why that is.

PS: Well, first of all the frequency of today's modern radio signals just keep getting higher and higher. I mean, now you have 5G mobile phones, Wi-Fi frequencies all going up well into the gigahertz band. They just keep getting higher and higher. And so, direction-finding antennas have to keep up. And as the physics has it, as the frequencies go higher, the antenna itself have to get smaller and perhaps, more importantly, the spacing between elements in an array has to get smaller. These antennas, to operate correctly, they require location on a Naval ship as high as possible for best reception. So naturally, the very top of the mast is the logical place. But guess what? Every single antenna would like that location.

Not to mention, you still need aircraft warning lights, lightning rod. Stuff like that has to go above there. And then, there's even higher priority antennas like navigation systems that, of course, get higher priority on location. So it's an expensive piece of real estate, if you will. So instead, the direction-finding antenna is traditionally placed around the mast-- around the upper portion of the mast where it can still have that optimal location, but allow other antennas and other systems to be mounted above it. This may be a wrap-around install antenna or an antenna itself built around what is an extension of the mast. That's how we usually do it in our case.

So there'll be a supporting mask going right through the center of the array. And this mast has to be thick enough not only to structurally support the stuff mounted above it, but also needs to pass through cables and whatnot to support everything above it. So as the frequency get higher, the antenna array gets smaller and smaller, like I was saying earlier. There's no way for a center of mass to go through it. So basically, it just can't keep up. Or what happens is these type of arrays get pushed off the mast to like a yard or something. And when that happens, their performance goes way down. They don't have the coverage, they're blocked in certain directions, and whatnot.

LP: So ideally, as you said, all antennas would be placed way up high on the mast. But this antenna stands out because it can be placed lower on the mast not taking up that valuable real estate.

PS: The fact that this antenna can be built around a mast and allow other antennas, other systems-- again, whether it be a navigation light or even a lightning rod-- to still be mounted above it is the significance of it.

LP: And although it's not at the very top, it's still reliable, still powerful.

PS: It's still reliable. It's still in an area where it doesn't get any blockage from the rest of the ship. So it's high above-- it's high enough above the superstructure of the ship.v LP: OK. So we're going to get a little bit into the electromagnetic spectrum. That may be a new term for some of our listeners. But the antenna operates in the ultra-high and super-high frequency bands of the electromagnetic spectrum. Why is it important to be able to reach those higher frequencies?

PS: Because those are signals of interest that intelligence-- for intelligence purposes, they're starting to operate in those bands. So you've got to--

LP: And by them--

PS: A cat and mouse game.

LP: Yeah. And by "them," we're talking about the enemy.

PS: It could be the enemy. It could be-- yes, it could be whatever. Whatever your purpose for--

LP: If it's for law enforcement, then--

PS: Law enforcement is another one. Yes.

LP: Yeah. OK. This particular antenna has to be able to collect those signals in those higher frequencies because that's the trend. That's where things are going.

PS: Correct.

LP: Yeah.

PS: They're still plenty down in the lower frequencies. It's just, there's more and more now becoming at the higher frequencies.

LP: All right.

PS: And again, if they know you can't operate up there, they're going to operate up there.

LP: So how many years was this award-winning antenna in development?

PS: The antenna itself was in development for well over three years, I'd say. Starting with an internal funding, where we performed some numerical research and built a proof of concept array. And then, of course, the design of the prototype antenna itself to get it ready for full production to our existing client. There was definitely a number of mechanical and environmental issues we had to work out in moving this antenna from a proof of concept to a production model. All this really, that's the way it comes together now, where there's individual elements that bolt around the mast versus, say, a single ray or a single piece that you would insert, say, over the mast.

LP: So about three years, then, you've been developing and researching and built a prototype, and now, we have a functioning antenna array that's winning awards. So what was the initial driving force to make this more compact, more powerful antenna array for ships? What did your team-- why did your team take on this challenge? And what is the backstory there?

PS: Well, before this antenna was conceived, so to speak, we were trying to find a solution to this problem all along. I mean, we knew it was coming. In fact, even our customer gave us a heads up-- "Hey, at some point, we are going to want to extend the frequency range of our existing antenna." So we knew it was coming. We looked at all a bunch of traditional methods just, here and there. Tried different beamforming methods. Just, really couldn't get anything together that would solve this problem-- again, an array that you could mount around a mast.

So finally, when our client did approach us, saying, hey, now we got some money or the funding is right around the corner, our option at the time was to just completely rebuild the upper portion of the mast to install what we thought would be the best option at the time, which would be a different, more, again, a traditional antenna array. We thought that was unfortunate because not only for the reduction in performance, but the existing antenna array that we were to retrofit, it had a large piece of unused real estate on the lower portion of its mast. We were just thinking, what a waste. If only, we could utilize that existing space. Plus, if we couldn't, we'd have to rebuild the upper portion of the mast entirely, and that would be expensive. Not only the redesign, but all the mechanical analysis that would have to be redone. You don't want the mast to break so definitely, there's some mechanical analysis that has to be done in redesigning the upper mast. But then, this idea came up of the slot array. And fortunately, we got some time before actual funding took place and was able to do some investigative work and start an IR. This started out as a quick look IR project.

LP: So for our listeners, the IR project, as you mentioned before, is internal research funding, funded by Southwest Research Institute for research and development. So this fell under that umbrella of SwRI-funded technology. And I, also, wanted to go a little bit further into the slot array, which we have talked about, but can you describe that a little bit more for us?

PS: It's known as the complement to the dipole array. And like we said earlier, Wheeler's concept involved tightly-spaced, small dipole elements. And so this is-- maybe you can think of it as just the inverse of that, where the slot element comes into play. Again, in the field, it's called the complement of it. | so, it's really, literally, just a slot in a big piece of metal that you feed at multiple points across that slot.

LP: When you did finally get that moment of, hey, I think we have an idea that works here? What was that moment like?

PS: Well, it was like, wow, something that may work. And of course, the first thing is, let's go after an IR-- internal research-- for this effort because the theory, the numerical modeling is showing positive here, but we definitely want to build some to make sure we're not missing something.

LP: Yeah. So you went--

PS: Build a proof of concept.

LP: So you went for it and found success. So that leads us to why we're here today, winning that big award. Tell us about the moment you found out your technology won the R&D 100 Award. How did that feel? And what does the award mean to your team?

PS: Well, it was really exciting. Never really won anything before, except for, maybe, perfect attendance certificates in grade school.

LP: And this topped that, I'm sure.

PS: Actually, I was in travel in Italy at the time. There was definitely a little delay in reading my emails. So it did come across to me as an email.

LP: Not a bad place to get good news.

PS: No. I guess, that's true. Definitely had to go celebrate over a beer with my colleagues.

LP: Yeah.

PS: But again, it was very exciting.

LP: Yeah. It's exciting for the entire Institute when we pick up another R&D 100 Award, so we all celebrate the team and the technology. Is the antenna currently deployed on Naval ships? And what's next for the technology? What do you envision for the future?

PS: Yeah. Our existing client that we designed this originally for, it is being installed in their class of ship. Right now, there's been two systems or antenna arrays delivered. And it's part of a retrofit process. So this is going to be over a five-year period that they retrofit their entire fleet.

LP: And this is not the end. This is only the beginning. So what's next--

PS: We hope. For sure. Yeah.

LP: --so what's next for the technology? What do you envision for the future?

PS: Well, we are definitely going to promote this to other navies amongst the Five Eyes countries, law enforcement applications. There's Coast Guard applications. Not to mention, even, maybe, land-based applications, where they may not necessarily need it for the original purpose-- again, which is to go around a mast-- but still, it does have some improved performance over the traditional antenna arrays, which is why you would want to use it.

LP: Very practical. So many possibilities. But I want to learn a little bit more about you, the engineer behind the technology. So tell us about your journey to designing antennas. What was your path to developing this type of technology? How do you get here?

PS: Well, I've been here at Southwest Research now for almost 30 years. Pretty much--

LP: One of our long timers.

PS: Yeah. A long timer, yes. And most of my projects had antenna design or antenna use somewhere in it, so I've definitely got my feet wet with messing with antennas, designing antennas.

LP: What did you study in school to get here?

PS: We had a good program for electromagnetics for undergraduate school. And definitely had my first antenna class there. And I went to graduate school and did more electromagnetic type work. A lot of that actually was in fiber optics, but definitely, it's all part of the EM theory. And then I got the job at Southwest Research and been messing with antennas ever since.

LP: So what do you enjoy about this work? Not very many-- I don't know very many people other than the people here at Southwest Research Institute that talk about antennas with such enthusiasm. So I think people don't realize what a pivotal technology it really is and everything that antennas do for us day to day. So what do you enjoy about this work that sometimes flies under the radar?

PS: Well, definitely, the satisfaction of seeing something be successful. I mean, of course, with all the successful work, there's always much more unsuccessful work that happens behind the scenes.

LP: Trial and error.

PS: You don't hear about that, but that's how you learn. Finding out that something doesn't work, that could be considered progress.

LP: Yeah.

PS: And of course, in my field, if you don't have any-- if you don't have any unsuccessful work, it's probably because you're not doing anything.

LP: Antennas don't always get the recognition that they deserve, right? Do you feel that way?

PS: Yeah. There is some truth to that because the antenna is the enabling technology in our work, but there's definitely, a lot of software behind the scenes and a lot of systems engineering, and they definitely get a lot of the credit. And credit deserved there, too. But sometimes, you're right, the antenna gets overlooked.

LP: So at Southwest Research Institute, our mission is to "conduct research and development to benefit humankind." How does this technology benefit and help humankind?

PS: Well, I believe this technology can be applied to many other things, not just for Naval shipboard use. Again, we mentioned law enforcement. In fact, that it has improved performance over your more traditional arrays makes this applicable to other situations, as well. I mean, I believe, we're just scratching the surface.

LP: Applicable to so many situations. Well, thank you so much for being here today, Patrick, and telling us about the award-winning Wideband Conformal Continuous- Slot Antenna Array. And thank you for being our guest on this five-year anniversary of the Technology Today podcast.

PS: I'm the lucky one. I'm the lucky one.

LP: That's right. Episode 61, five years.


And thank you to our listeners for learning along with us today and through all 61 episodes over the last five years. You can hear all Technology Today episodes, and see photos and complete transcripts, at Remember to share our podcast and subscribe on your favorite podcast platform.

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Ian McKinney and Bryan Ortiz are the podcast audio engineers and editors. I am producer and host, Lisa Peña.

Thanks for listening.

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