The invention of radio communications in the 1890s was a discovery that changed the world.A signal could be coded into an electromagnetic radio wave, sent forth into the world, and picked up by a receiver, which translates and converts the signal back to an understandable format.With current technology, the electromagnetic signal is typically converted into an electrical signal and digitized into numbers, which can then be processed to extract the information it carries.Now, a team of researchers led by Southeast University in China has shown that some of those calculations can instead be performed directly on the radio waves as they interact with a programmable surface."In an everyday analogy, it can be viewed as a reprogrammable electromagnetic-space computer to process the signals directly in the electromagnetic wave propagation," electrical engineers Jun Yan Dai, Qiang Cheng, and Tie Jun Cui, the study's corresponding authors, told ScienceAlert."The computed results are carried out directly by the outgoing electromagnetic wave, without requiring to firstly convert the entire signal into digital data for processing by a conventional processor."
Radio waves occupy the low-frequency end of the electromagnetic spectrum – basically, light – and have a set of properties that make them especially useful for transmitting information.They can travel long distances through the atmosphere, diffract around obstacles, travel through some materials, and many can travel through weather that interferes with shorter wavelengths. We use them for all sorts of technology, from Wi-Fi to radar to GPS to broadcast media.But transmitting a radio wave is only part of the job. For many applications, we also need to precisely manipulate those waves – changing properties such as their direction, phase, or amplitude.One increasingly powerful way to do that is with a metasurface – a thin, engineered surface covered in tiny structures designed to alter electromagnetic waves in carefully controlled ways.A diagram illustrating how the metasurface switches between Fourier transforms and convolutions. (Chen et al., Nat. Commun., 2026)The metasurface developed by the research team takes that idea a step further. Its properties can be electronically reprogrammed, allowing the researchers to change how an incoming radio wave is manipulated over both space and time."This architecture builds on the long-term development of time-coding metasurfaces. In 2018, our group introduced the concept of time-domain digital coding metasurfaces, extending the metasurface control from the static spatial domain into the time domain," the researchers explained."Building on this foundation, we established a direct relationship between time-coding sequences and mathematical operations such as Fourier transforms and convolutions. This allowed the metasurface to move beyond controlling electromagnetic waves and to use electromagnetic waves as a computational medium."They chose the two operations mentioned – Fourier transforms and convolutions – because they represent two of the most fundamental operations in signal processing.A Fourier transform is an operation that breaks a pattern up into its parts – think of separating a chord into its constituent notes, or a white beam of light into a rainbow. That's the simplest explanation, but the math involved is more complicated.
