An antenna seems, at first glance, one of the simplest components of an electronic device. It receives or emits electromagnetic waves and, depending on its design, works at certain frequencies. But What if you could change its properties on the fly? What if the same antenna could be adapted to different frequencies according to the needs of a network, a radar or a satellite?
A team of scientists from Queen Mary University of London has taken a step towards that possibility by modifying a material on an extraordinarily small scale: that of atoms. The result, published in Science Advances, is a new type of material capable of responding much more flexibly to electric fields and that has already been incorporated into prototypes of antennas and microwave devices.
The key is a ceramic called strontium tantalate (basically mixed ceramic oxide of strontium and tantalum). The scientists, led by Yang Hao, They replaced a small proportion of their strontium atoms with slightly smaller calcium atoms. The change seems insignificant, but it introduces small deformations in the crystal structure. And those imperfections do something unexpected.
They create tiny electrically active regions, known as polar nanoclusters, within a material that does not normally exhibit that behavior. These regions can respond quickly to an electric field and modify the electromagnetic properties of the material. “It’s a little How to find a way to add dimmer switches to a system that previously only had an on and off position”Hao points out.
But beyond chemistry and technology, what does this mean? A conventional antenna is designed to perform optimally under certain conditions. If we want to substantially change its operating frequency, normally we need to physically modify some of its elements or resort to additional components.
With a tunable material, however, the antenna itself can electrically change its characteristics. That’s where the calcium atoms come in, demonstrating an unusual combination of three properties: a high capacity to modify its electromagnetic response, low energy losses and stable operation over a wide frequency range.
This balance is important because there is a problem that has been complicating the development of tunable electromagnetic materials for years. Materials that can easily change their properties often pay a price: They lose more energy or perform worse when the frequency increases. The new material seems to reduce that commitment.
“Our work shows that very small changes at the atomic scale can have an extraordinary impact on the behavior of a material – adds Hao -. By engineering a microscopic deformation between the layers of a crystal, we were able to create dynamic polar regions that provide strong tunability without the drawbacks usually associated with conventional ferroelectric materials.”
The difference between an interesting lab property and a useful technology, however, is getting it to work in a real device. And here the team went one step further. Hao’s team incorporated the material into prototype antennas and microwave devices and demonstrated that they could modify their operating frequency using both an electrical voltage and temperature changes. That opens up an especially attractive possibility for wireless communications.
Today’s networks have to handle more and more information and work in highly variable conditions. Mobile phones, satellites, radars, navigation systems and billions of connected devices use different frequency bands and they need to adapt to an increasingly congested radio environment. An antenna capable of dynamically modifying its behavior could, for example, change frequency when a certain band is saturated, adapt to different transmission conditions or perform different functions without having to physically replace its components.
“Wireless technologies are becoming more sophisticated and that creates the need for materials that can be adapted quickly and efficiently – concludes Hangfeng Zhang, co-author of the study -. Our work shows that small changes at the atomic scale can have a surprisingly large effect on performance”. Potential applications go beyond antennas: adaptive communications networks, microwave devices and advanced sensing systems. In the current technological context, an intelligent and adaptive antenna is a great step forward.