Satellite Internet services are expanding rapidly, but the ground terminals required to connect to them are expensive and power hungry. The French startup Greenerwave is building a terminal that uses something they call a “reconfigurable intelligent surface” (RIS) to reduce both costs and energy consumption.
Constellations of low earth orbit (LEO) satellites from companies like Starlink and Eutelsat OneWeb promise to provide connectivity anywhere in the world. But establishing links with satellites that are constantly on the move, and rapidly switching between them to maintain a reliable connection, requires some advanced antenna technology.
Most services today rely on phased-array antennas, which are made up of multiple smaller antennas that work together to shape and steer radio beams. This makes it possible to lock onto a moving target, but it requires complex and costly electronics that use a lot of electricity. Paris-based Greenerwave has instead built a terminal that relies on an RIS, which is made up of scores of small, adjustable reflective units that work in concert to alter the direction and properties of a beam as it is reflected off the surface.
Because the antenna uses much simpler electronics, CEO Geoffroy Lerosey says it is more cost-effective than those relying on a phased array and cuts energy down to one-tenth of traditional systems. Beyond slashing costs, RIS technology, he says, could also enable new applications such as satellite terminals on cars and planes. Lerosey says Greenerwave plans to start sales of their terminal by the end of the year.
He also reports that Greenerwave is in discussions with the Tysons Corner, Va.–based satellite multinational company Intelsat to develop a custom terminal. Contacted about this statement, an Intelsat spokesperson confirmed the memorandum of understanding between the two companies and said, “Greenerwave’s innovative terminal technology fits very well within the Intelsat multiorbit strategy. Greenerwave’s low-cost, low-power products will differentiate our services in the market and help enable a broader range of satcom applications.”
Greenerwave’s RIS satellite Internet ground terminal has a small enough footprint and modest enough energy budget to imagine new applications on cars and drones. Greenerwave
“We are bringing antennas that are more cost effective than the competition and also much lower [power] consumption,” says Lerosey. “But we are also allowing new verticals to use this kind of technology because of the low-power consumption.”
Metamaterials make better tuned wavefronts
Establishing a communication link between a moving satellite and a ground station on Earth requires both to be able to steer radio beams toward each other—one to beam data up and another to beam it down. This is typically done using phased-array antennas that use a process called beamforming, in which many tiny antennas transmit signals with different phases. These signals interfere with one another, either constructively or destructively, and by carefully controlling this pattern of interference, the antenna generates a single radio beam whose shape and direction can be controlled.
In contrast, Greenerwave’s terminal uses technology based on research that Lerosey carried out at the Institut Langevin in Paris on “metamaterials”—engineered materials that have properties not normally seen in nature. At the heart of the company’s device is a 2D metamaterial known as a metasurface, which is designed to manipulate electromagnetic waves. It is made up of many small reflective elements that can be switched between high and low electrical impedance, which alters the phase of any wave that bounces off them.
Whena radio beam is fired at this surface, the reflective elements produce signals with different phases, similar to the tiny antennas in a phased array. These interfere with one another to create a radio beam whose direction, phase, polarization, and even bandwidth can be precisely controlled. The antenna can even create multiple beams whose properties and direction can be independently configured.
The big difference between antenna technologies, Lerosey says, is that each antenna in a phased array requires a dedicated integrated circuit. And that increases the complexity, cost, and power consumption of the overall system. By contrast, the electronics in Greenerwave’s terminal, he says, are comparatively modest. “The building block of this surface is just a very simple switch,” says Lerosey. “It’s just a few transistors. It’s really small. It costs very little money, and also it consumes very little energy.”
Most steerable antennas typically use somewhere between 500 watts and 1 kilowatt of power, but thanks to the metasurface antenna’s passive beamforming approach, Greenerwave’s terminal will use just 70 W, Lerosey says. That could open up new applications where energy efficiency is crucial, such as installing satellite terminals on vehicles or drones.
While the hardware is simple, precisely controlling the RIS requires some complicated software, Lerosey says. There is no equation that can directly predict how a particular pattern of reflectivity will impact the direction and properties of the beam, he says. So the company has created a digital twin of the terminal, based on a combination of physical models of the system and AI models trained on real-world operational data. This digital twin is then used to calculate how to reconfigure the patterns of reflectivity to achieve the desired beams.
Bill Ray, a distinguished VP analyst at Gartner, says metamaterials have significant potential for reducing costs in satellite communications. That could expand the use of satellite connectivity, he says, for example making it feasible to embed a terminal in the roof of every car. “There are questions about consistent production quality,” he says. “But academic experiments have shown the potential, so I’m not surprised to see commercial companies moving quickly to exploit the technology.”
In February, Greenerwave announced that it had raised €15 million to develop its first production terminal, which Lerosey says will be available by the end of the year.
Lerosey says their ambitions go beyond satellite communications, and the company is currently developing terminals that could be used in 5G networks. Their technology’s reduced energy consumption could prove appealing for network providers, he says, but he anticipates it will be some time before the technology is standardized.
UPDATE 3 May 2024: The story was updated to include confirmation and a statement from an Intelsat official about a deal struck with Greenerwave.
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