Researchers have taken a step toward developing a type of antenna array that could coat an airplane’s wings, function as a skin patch transmitting signals to medical implants, or cover a room as wallpaper that communicates with Internet of Things (IoT) devices.
The technology, which could enable many uses of emerging 5G and 6G wireless networks, is based on large-area electronics, a way of fabricating electronic circuits on thin, flexible materials. The approach overcomes limitations of conventional silicon semiconductors, which can operate at the high radio frequencies needed for 5G applications but can only be made up to a few centimeters wide and are difficult to assemble into the large arrays required for enhanced communication with low-power devices.
To achieve these large dimensions, others have tried discrete integration of hundreds of little microchips. But that’s not practical — it’s not low-cost, reliable, or scalable on a wireless systems level. The new technology can natively scale to large dimensions such as computer monitors and liquid-crystal display (LCD) televisions. These use thin-film transistor technology, which the team adapted for use in wireless signaling.
The researchers used zinc-oxide thin-film transistors to create a 1-foot-long (30-centimeter) row of three antennas in a setup known as a phased array. Phased antenna arrays can transmit narrow-beam signals that can be digitally programmed to achieve desired frequencies and directions. Each antenna in the array emits a signal with a specified time delay from its neighbors and the constructive and destructive interference between these signals adds up to a focused electromagnetic beam. A single antenna broadcasts a fixed signal in all directions; a phased array can electrically scan the beam to different directions, enabling point-to-point wireless communication.
Phased array antennas have been used for decades in long-distance communication systems such as radar systems, satellites, and cellular networks but the new technology could bring new flexibility to phased arrays and enable them to operate at a different range of radio frequencies than previous systems.
Large-area electronics is a thin film technology, so circuits can be built on a flexible substrate over a span of meters. All the components can be monolithically integrated into a sheet that has the form factor of a piece of paper. The team fabricated the transistors and other components on a glass substrate but a similar process could be used to create circuits on flexible plastic.
This type of antenna system could be installed almost anywhere. When used like wallpaper in a room, it could enable quick, secure, and energy-efficient communication with a distributed network of IoT devices such as temperature or motion sensors. Having an antenna that’s a flexible surface could also be beneficial for satellites, which are launched in a compact format and unfold as they reach orbit, and a large area could be advantageous for long-distance communications with aircraft.
With an airplane, because its distance is so far, much of the signal power is lost, as is sensitivity. The wings are a fairly large area, so if there is a single-point receiver on that wing, it doesn’t help; however, if the amount of area that’s capturing the signal can be expanded by a factor of a hundred or a thousand, signal power can be reduced and sensitivity of the radio can be increased.