Currently, terrestrial cellular networks cover only 20% of the planet. Communicating in out-of-range areas is either impossible or relies on a costly satellite link. This challenge was the primary motivation for the European Space Agency (ESA) to launch an ambitious call in 2020 for projects in the field of high-performance, ultra-miniaturized antennas.
400 MHz frequency with a 3 cm thick antenna!
With the support of CNES, CEA-Leti and the startup Kineis successfully overcame this challenge by validating the potential of their technology during a demonstration that lasted several weeks. ESA’s primary requirement for this project was to achieve sufficient miniaturization, in other words: how to efficiently transmit a radio signal at a frequency of 400 MHz using an antenna that is only 3 cm thick, when the laws of physics generally require a thickness of 37 cm?
In addition, these antennas had to be "circularly polarized" (have the same range) no matter the orientation of the equipment. For example, a shipping container fitted with a tracking antenna has to be able to deal with challenges such as the rolling and pitching of the container during transport or a tilted container when lifted by a crane. A successful antenna was one that would ensure communications despite these changing situations.
"There are many applications with a metal support, which are strategic for Kinéis, but they are detrimental to the efficiency of most antennas. CEA-Leti's proposal provides a high-performance solution for these demanding conditions," adds Vincent Gamonal, Test, Validation and Certification Engineer at Kinéis.
Electronically controlled micro-antennas
“We met both of these requirements thanks to our expertise in the miniaturization of antenna elements,” explains Serge Bories, Project Manager at CEA-Leti. “Our 3 cm antenna is actually a microarray of even smaller antennas. Capacitive coupling serves to control the distribution of radio frequency currents.”
“The antenna also allows for transmissions at 868 MHz over terrestrial IoT networks. We switch to this frequency when the equipped object returns to an area covered by the terrestrial cellular network,” explains Christophe Delaveaud, Head of CEA-Leti's Antennas and Propagation Laboratory. “As a result, communication is cheaper and requires less energy”.
60% improvement in message delivery
The demonstration carried out in 2023 at Kineis' Toulouse facility revealed a spectacular level of performance. Despite the equipment's miniaturization, radiated energy was multiplied by 20 when compared to the best antenna currently used by Kineis, all the while maintaining an equivalent level of power consumption!
“We've measured a 60% improvement in the number of messages received by Kinéis satellites,” adds Serge Bories. “The energy gain means that data can be transmitted in situations where the antenna and satellite are not in direct view of each other, for example, if other objects are partially blocking them.”
Taking it to the next step with industrial partners
"Developing such a small circularly polarised antenna was a huge challenge, but CEA-Leti's prototype has achieved the desired objective. What now remains is the industrialisation stage, to turn it into a product that can be used by our customers," says Vincent Gamonal.
This ultra-miniaturized antenna can already be deployed for the surveillance of agricultural herds in remote locations. For more demanding applications (maritime transport, defense, agriculture, personal safety in hostile natural environments, etc.), CEA-Leti is ready to improve the technology even more:
“We want to equip this system with a feedback loop that will detect and correct any disturbances induced by objects in the immediate vicinity," explains Serge Bories. “These improvements open the door to collaborations with industrial partners."
Dual connectivity ultra-miniature antenna (Sat/Terr IoT)