As constellations of low-Earth-orbit (LEO) satellites displace geosynchronous (GEO) satellites, the antenna OEMs are preparing for a new world of inflight connectivity (IFC).

“Because the LEO satellites are significantly closer—hundreds of miles as compared to tens of thousands of miles away—the data goes up and back faster, and your [inflight] internet looks more like it does at home,” explains Steve Newell, chief commercial officer for Nxtcomm. “Since all of the timing and delays associated with long-distance satellites are completely obliterated, you can support a higher bandwidth with significantly lower data latency existing in GEO orbits—and with a much smaller antenna providing faster service for those in the cabin.”

Newell reports that the company is developing its Nxtcomm ESA (electronic steerable antenna) for both the defense and commercial airline markets, with two defense-related buyers as launch customers—L3Harris Technologies and another, undisclosed. L3Harris and the unnamed customer are to receive Nxtcomm ESA K_a- and K_u-band antennas, respectively, to support global defense applications in LEO. Delivery is slated for 2022.

“Now that we have those well underway, we have defined timelines from LEO manufacturers and from LEO satellite providers,” says Newell. “When those timelines line up with what we’re going to provide the market, we’ll have products to support IFC opportunities with both commercial and business jet offerings—likely by the end of 2022 at the earliest.”

According to Newell, the Nxtcomm ESA is a lighter-weight flat-panel device, which demands less from the aircraft’s power supply due to the efficiency gained from its unique aperture. “Nxtcomm has been driving that efficiency through the aperture to the feed networks and all the other complexities that go into building the ESA to generate more gain for the customer,” he says.

Nxtcomm’s ESA has also been designed with scalability, in that its subarrays, built in a recombined fashion, can be applied to various market segments without the need to redesign the core. That means the same panels being built for defense applications can simply be repackaged to be readily available for civil aviation, Newell says.

ThinKom Solutions has gone beyond ESA with its patented “variable-inclination continuous transverse stub” (VICTS) technology. According to Greg Otto, the Hawthorne, California-based company’s vice president for sales and marketing, VICTS combines the technical benefits of mechanically steered antennas and ESAs, with none of the limitations of the mechanical devices.

He points out that as of mid-2021, ThinKom’s VICTS phased-array antennas were in service on more than 1,550 active aircraft, with an accrued total of 23 million flight hours and with more than 100,000 hr. of mean time between failures (MTBF). To illustrate, Otto reports that ThinKom’s first Ku3030 antenna, incorporating VICTS, installed on an Aeromexico aircraft in 2015, has never been removed for servicing.

Unlike mechanically steered gimballed dish antennas, the VICTS antennas are lower-profile—3-4 in. high—which minimizes aerodynamic drag, says Otto. He adds that their low inertia platters and kinematically simple drive system “support very rapid beam agility,” allowing for a very fast—less than 1 sec.—break before “making intersatellite handoffs” on next-generation LEO constellations.

“Compared to ESAs, VICTS antennas provide superior gap-free pole-to-pole coverage, including extremely low look angles, higher throughput and superior spectral efficiency,” Otto states. “ESAs also tend to be far more power hungry, resulting in thermal management issues, which may require additional liquid cooling systems that add weight, expense and maintenance. Also, VICTS antennas are able to provide gate-to-gate connectivity—even under high ambient temperatures with full solar loading.”

Otto points out that with LEO vehicles, the satellites will be continuously moving rapidly across the sky, so the antenna must have the ability to disconnect from one “setting” satellite and connect with one that is “rising” quickly. However, a greater challenge is for the antenna to be interoperable with GEO constellations as well as those in non-geosynchronous orbit (NGSO). “The VICTS antennas are fully capable of adapting to LEO as well as medium-Earth-orbit (MEO) and new-generation GEO high-throughput satellites (HTS), based on numerous over-the-air testing by ThinKom,” he reports, adding that in many cases, only addition of a new modem and possibly a global navigation satellite system antenna will be needed.

With more K_a-band networks coming into service, ThinKom has ramped up production of its Ka2517 antennas to meet growing demand. The Ka2517 has been selected for Inmarsat’s next-generation GX+ global broadband IFC, including the GX+ North American service being rolled out by Inmarsat and Hughes Network Systems. “We are also supplying Ka2517 systems to several major airlines in partnership with other network providers, some of which are yet to be publicly announced,” Otto says.

Some of the new-generation NGSO and GEO networks will operate in the millimeter-wave Q and V bands (37.5-42.5 GHz and 47.2-51.4 GHz), says Otto. They will augment the existing K_u- and K_a-band networks.

“We recently announced a new VICTS phased-array antenna designed specifically for operation on these higher frequencies,” he says. “The new Q-/V-band user terminal supports two simultaneous full-duplex beams that can independently be pointed at two different satellites, providing uninterrupted ‘make-before-break’ connectivity.” This ensures uninterrupted services while switching between rising and setting satellites and also allows multiple satellites or channels to be bonded, either within the same or even across different satellite constellations, he explains.

Asked if LEO or MEO IFC services are available for commercial airline passengers now, Otto says they are not but confirms that the satellite companies are already putting them into orbit, with the likelihood of limited connectivity services commencing during 2022.

“Next-generation terminals need the flexibility to comply with multiple networks, operators and orbits,” notes Danny Frai, director of product market-aero at SatixFy Israel. “This is achieved with a combination of technologies such as digital beam-forming, true-time-delay and multi-beams. We have developed our own silicon chips in order to achieve this,” he reports.

Frai says that the company’s latest product, Aero terminal, is available in K_u- and K_a-bands, with an optional dual-band implementation, based on SatixFy’s unique electronically steerable multibeam antenna (ESMA) technology. He adds that the Aero terminal is actually a full terminal, comprising antenna, RF (radio-frequency) power amplifiers, low-noise amplifiers (LNA), a tracking engine, antenna controller and modem. “It is a full 2D-scanning, all-electronically steerable antenna with advanced multi-beam capability, allowing for simultaneous communication with multiple satellites,” Frai says.

The Aero terminal has the capability to work with LEO and MEO constellations as well as traditional GEO services. In fact, according to Frai, a unique feature is simultaneous LEO, MEO and GEO full support with a totally flexible software-defined antenna and an embedded software-defined radio modem for multiple-network support. Other features, he says, include proven digital beamforming, already tested on a commercial flight, and a unique digital true time-delay implementation, allowing for multi-beam, higher bandwidths and flexible array size.

“Aero terminal is a very low-profile terminal—power-in/Ethernet-out—with no need for any in-cabin components,” Frai says. SatixFy plans to offer an ARINC 791/2-compliant IFC terminal, planned for certification during 2022; however, a smaller, more optimized version for LEO could be certified earlier, he notes. The target aircraft for certification is currently the Airbus A320.

Mike Pigott, executive vice president for connectivity at Santa Ana, California-headquartered Anuvu, reports that the company has focused on mechanically steered antennas as components of its Airconnect connectivity platform.

“These antennas are extremely capable gimbal [mechanically steered], low-risk and proven reliable,” Pigott says. “They fill many of the requirements with higher RF performance at all look angles—something that will never be available with flat panels—along with low power and reasonable cost, although they do make compromises with a slightly higher profile and longer satellite-switch times,” he adds. “For the longer handoff, we have simulated a managed satellite-handoff process that demonstrates a seamless user experience with data buffering and fast modem lock.”

Pigott disputes claims that mechanically steered antennas are less reliable than ESAs, which have no moving parts but do have thousands of electrical elements with hundreds of active electronic parts, all of which are exposed to wide temperature swings.

“It’s unproven whether ESAs will operate with any more reliability than a mechanically steered antenna currently operating at 80,000 hr. MTBF,” he says, adding that the Anuvu antenna’s passive micro-horn array consumes no power in the collection of RF energy. In contrast, an ESA’s electronics require power in the 1,000-2,000-watt range, generating heat that is more difficult to disperse on the ground. 

“Reliability has a direct correlation to part temperature and thermal management, which is a significant engineering factor to resolve,” says Pigott. “At the same time, we have full band capability, while ESAs have a restricted bandwidth of several hundred megahertz.”

The Anuvu family is designed to work with all satellite constellations using the full International Telecommunications Union bands, enabling it to support all K_u and K_a bands and future constellations in development. In fact, the antennas are currently in use on Air France and Turkish Airlines narrowbody aircraft. “We have demonstrated our first-generation K_a-band antenna on Telesat LEO. Our second generation is due for release in early 2022,” Pigott notes.