Finding the Right Fit: How Antennas Are Evolving for IFC
In-Flight Entertainment and Connectivity (IFEC) is fueling massive needs for throughput on aircraft antennas, yet airlines don’t want bigger devices to bolt on their planes. Antennas need to get smaller and more capable, and as airlines equip for new passenger demands, they want antennas to be that way now.
Airplanes need antennas, and lots of them. Some can carry well over 60 for a variety of purposes, but one has come to the spotlight — the antenna for passenger connectivity. This much-needed device is the gateway for in-flight Wi-Fi, but make the antenna too big, and you increase the amount of fuel the airline needs. Make the antenna too small, and it will fail to meet bandwidth demands. The right In-Flight Entertainment and Connectivity (IFEC) antenna must balance this dichotomy, and that is where antenna manufacturers find themselves today.
IFEC is creating new needs for a sector that doesn’t necessarily move at breakneck speeds. Asked if aeronautical antenna technology development is moving faster or slower than expectations in recent years, Norman Haughton, manager of IFEC product design at Air Canada, gives a curt answer: “slower.”
“In my words it’s nothing revolutionary compared to the consumer electronics world and the pace that they are moving. Understand that we are talking about aerospace. Nothing moves as fast, but I think there is lots of room for improvement,” he says.
Haughton does note evidence of major breakthroughs in antenna technology, but still finds it in general, underwhelming. He mentions the advances seen in the mobile world where cell phones got smaller, thinner, lighter, and more powerful in a relatively short period of time. Aircraft antennas have not developed at that pace.
“The biggest breakthrough that’s needed is a super flat array: something that essentially you paint onto the airplane that doesn’t impact aerodynamics. That is one of the biggest issues with antennas and radomes: the inability to be efficient when it comes to fuel. It’s one thing to provide the service, but it’s another to keep the airline’s operating costs down,” he adds.
Antenna manufacturers say they know and recognize the changing needs of their Original Equipment Manufacturer (OEM) and airline customers. IFEC antennas need to support more data, take up less space, and require fewer repairs than before to keep these customers satisfied.
“We’ve seen the expectations of the airlines and their customers steadily evolve from general satisfaction with the ‘older’ lower data rate ‘closed’ regional solutions of the not-too-distant past to the ‘newer’ higher data rate ‘open’ global connectivity passenger demands of today,” says Bill Milroy, CTO of ThinKom, manufacturer of Gogo’s 2Ku antenna. “From an antenna-centric viewpoint, this necessarily drives us to smaller higher-efficiency, multi-band/multi-purpose antennas which can globally support higher data rates (to keep paying passengers satisfied) and do so more economically (to keep IFEC service providers' satellite bandwidth costs affordable).”
The requisites to accomplishing those high data rates lie in, among other things, a capable directional array that can achieve the right gain, explains John Borghese, VP of Rockwell Collins' Advanced Technology Center. These directional arrays have until recently been almost exclusively mechanically steered for business jets and commercial aviation aircraft. And while they have fulfilled airline needs, mechanically steered arrays come with significant setbacks.
“The challenges with those are they are very large, so they require a footprint on top of the aircraft that generally creates drag,” says Borghese. “They have to have very sophisticated mechanical steering to make up for the movement of the aircraft, which means a lot of expense, and they are mechanical systems so the reliability is not where it would be desired.”
An Electric Solution
Electronically Steered Antennas (ESAs) are emerging as the new favored technology to solve the cumbersome directional array problems introduced with mechanical systems. In comparison to their mechanical counterparts, ESAs lack moving pieces, yield higher throughputs and do so without taking up as much space. They very well could be a “magic bullet” solution — if they can overcome their own unique challenges.
The principal barrier for ESAs in the commercial world is cost. Electronically steered/ phased array antennas have seen use predominantly in the military where their capabilities are demanded regardless of their high price tag. Borghese says the radio modules that comprise an ESA generally drive the costs out of reach in the commercial sector. For example, each radio module — with all its transceivers, amplifiers, Radio Frequency (RF) circuitry and other components — can cost $1,000 or more individually. Make that array into a 30 by 40 system, and your final antenna easily costs more than a million dollars.
There is technology that is driving those costs down, however. Borghese points to Silicon Germanium RF Integrated Circuits (RFICs) that enable manufacturers to put several circuits both digital and RF onto one device at high frequencies like Ka and Ku as one such example.
“There are a couple of new technologies that hope to allow for a commercial low profile antenna,” adds Todd Hill, Panasonic Avionics’ senior director of Global Communications Services (GCS)-satellite services. “First is the combined RF and digital Application-Specific Integrated Circuit (ASIC) technology being driven by the self-driving car and Wi-Fi technology; second is the technology being developed by Kymeta. Both of these have a real potential to bring low profile antennas to commercial airplanes.”
Stretching beyond the military domain, both established companies and entrepreneurs are now bringing new ESA technology to the market in hopes of shedding enough cost to make them competitive with mechanical systems. One such company, Phasor, has been developing an ESA antenna for more than six years, and is in the midst of productizing the technology. Anticipated to be astoundingly lower cost than government phased array systems, and measuring less than about 2.5 centimeters thick, the company expects to bring a scalable, conformable antenna to the market in the not too distant future.
“We will have a much thinner, lighter, more capable software controlled and defined antenna, which gives a lot of flexibility and robustness to the network service provider and ultimately the end users/ aircraft passenger,” says David Helfgott, CEO of Phasor. “The technology in itself is better suited to that use case than a mechanical antenna might ever be.”
Antenna manufacturers are exploring new ways to produce antennas. Borghese mentions developments with 5G in the mobile industry that could lead to ESAs in future cell phones. At Rockwell Collin’s Advanced Technology Center, he says the company is researching ESA technology not just for airborne, but for multiple applications. Part of that discovery process is asking the right questions.
“Can you turn a printed circuit board — the same circuit cards that we use to put electronic components on that we put into our black boxes — can we turn that into a high performance antenna?” he muses.
Helfgott says Phasor has completed nearly 100 tests on its forthcoming antenna. He describes the productization phase as a long, deliberate process that remains on schedule. The core technologies — transmit, receive, tracking, the algorithms, the chip design and the system architecture — are all done. The next step, he says, is working with partners to specialize products for different markets, with aviation being one of them.
Borghese mentions new technologies such as lower cost Gallium Arsenide, and the adoption of 3-D printing as two continuing trends in antenna technology. He anticipates new technologies and the resulting reduction in cost will allow the use of ESAs for multiple applications.
“For aeronautical antennas, I’d have to say that conventional Numerical Control (NC) machining, stamping, casting, and extruding are still the norm, but we can certainly see additive-manufacturing playing a more important role going forward, either for fabrication of subassemblies or (in some cases) entire antennas,” adds Milroy. “Further, we widely employ injection-molding in many of our ruggedized fixed and ground-mobile antenna products here at ThinKom, many operating in some very challenging temperature and vibration environments, and we envision eventual applicability of these to our aero-markets as well.”
HTS and NGSOs
With the exception of Gogo’s Air-to-Ground (ATG) network in the United States and other regional ATG networks underway by SmartSky and Inmarsat/Deutsche Telekom, In-Flight Connectivity (IFC) is essentially a satellite game, and right now satellites are going through an evolution of their own. High Throughput Satellites (HTS) employing spot beams and frequency reuse are escalating the level of capacity available from orbit. Also, multiple companies are studying or already building and launching Non-Geosynchronous (NGSO) satellites tailored for connectivity applications. This in turn is putting new requirements on antennas.
Borghese describes HTS as the future of meeting consumer expectations for internet connectivity. Rockwell Collins is a value added reseller for Inmarsat’s Ka-band Global Xpress HTS system, as well as a partner with newcomer OneWeb on the company’s aeronautical service. He says new Low and Medium Earth Orbiting (LEO/MEO) satellite systems open up opportunities for additional capability globally and over polar routes compared to Geosynchronous Orbit (GSO) where the further from the equator a plane is, the harder it is to maintain a link.
“High Throughput spot-beam satellites are pushing IFC antennas to broader satellite operating (‘tunable’) bandwidths in support of open global ‘any place, any satellite’ flexibility and broader channel (‘instantaneous’) bandwidths, as individual transponder bandwidths are moving up from today’s standard 36 MHz to much larger 125, 250, and even 500 MHz in upcoming HTS and [Extreme High Throughput] ‘XTS’ implementations,” says Milroy. “In terms of emerging NGSO satellite constellations, these share the same operating and channel bandwidth trends as GSO-based HTS, but in addition, push IFC antennas to support five to 20-times higher antenna beam agility (angular velocities and accelerations) in order to accommodate the much more challenging tracking and hand-off requirements uniquely associated with NGSO operations.”
HTS systems are the satellite industry’s move to keep pace with implacable passenger demand for connectivity. Future NGSO systems, which may also be HTS, follow a similar motivation of bringing boatloads of capacity online. Moreover, leaving the geostationary arc means satellites can provide coverage beyond 65 to 70 degrees latitude, enabling polar and near polar routes to still be connected. But the complexity introduced through HTS and NGSO systems means antenna companies will need to keep pace as well. Panasonic’s Hill believes that mechanical systems will still have an important role to play in this future, though not everyone agrees.
“HTS fit well with existing mechanically steered antennas and future low profile antennas,” he says. “Operating with NGSO satellites from airplanes can be accomplished in theory with current mechanically steered antennas, but the real potential is with low profile antennas that can track two satellites simultaneously.”
Most put much more emphasis on ESAs as the preferred technology to connect with HTS and a must-have for keeping track of NGSO satellites. Borghese says ESAs have enough benefits with drag and reliability that they could be the de facto choice for GSO-HTS over mechanical systems, but for LEO systems he changes tone, calling them “absolutely necessary.” This is because LEO satellites are only visible for a few minutes at a time, so a mechanically steered antenna would need two arrays to track spacecraft, and even then that might not be enough.
“If you are going to have a continuous signal then you need to switch from satellite to satellite every couple of minutes; a mechanically steered array can’t do that,” says Borghese.
Antennas of the Future
Though the aviation antenna sector might move slower than Apple, Samsung, or Huawei, that doesn’t mean things won’t look very different only a few years from now. Haughton says Air Canada seeks out efficient, aerodynamic antennas as part of its total connectivity solution, with passenger experience top of mind. Five years from now he anticipates some major changes.
“I expect that they will be lighter. I expect that they will accommodate way more throughput. I expect that on the external of the airplane it will be so thin that they are not noticeable, and most arctic flying and semi-arctic flying won’t be impacted by the type of radome or antenna that the airline selects,” he says.
Borghese believes future antennas will meet the needs of the OEMs and airlines, including higher bandwidth, and will have the ability to connect to the internet and TV at the same time. Furthermore he anticipates aircraft antennas will be reliable and redundant enough that antenna replacement for maintenance will be at B checks only. Milroy echoes similar points, saying that based on current trends, he expects the industry push to smaller, more efficient, wider bandwidth, and higher beam agility IFC antennas.
Phasor intends to launch in the aviation market in six months after launching products for land mobile and maritime. Helfgott says the company already has significant commercial interest for its product and is in multiple discussions with potential customers and partners. He anticipates his company will have a substantial lead on other new ESA developers because of all the time and effort already invested.
“We know very well how much work it takes to go from concept to working prototype, from working prototype to tested/proven technology, and from technology to an actual launchable, licensable product … people who are announcing new phased arrays have a lot of work in front of them and we’ll be on our third or fourth generation by the time they come to market,” he says.
Helfgott says Phasor will be extremely competitive in aviation for those needing 50 to 100 or more Mbps. He highlights having the right go-to-market partners for the first initial years to make sure the company meets the unique attributes of each market/use-case.
Panasonic Avionics is working steadily with an in-house antenna development team as well as third party providers to develop what Hill describes as “the next breakthrough technology.” He says low profile antennas are entering a very exciting phase, and that even outlandish-sounding ideas about future antenna systems may not be all that far-fetched at all.
“We joke about paint-on antennas but I think that is a little more than five years away. I think low profile antennas will be available that are the same price as mechanically steered versions,” says Hill. GCA