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An ordinary camera captures light reflected from objects and builds a picture from it. But if the object is hidden behind an obstacle or does not reflect light, radio waves come to the rescue: they pass through walls and fog, and a computer reconstructs the image from scattered signals. The problem is that a clear picture requires many different signals, which means a wide frequency band — expensive and inconvenient.

Researchers proposed twisting radio waves, giving them orbital angular momentum. Such a wave does not move like a flat sheet but like a corkscrew, screwing into space. Each 'turn' is a new way to illuminate the object, providing additional information for the computer. In the prototype, waves are generated inside metallized 3D-printed cavities, and special dielectric lenses impart the desired rotation.

The result surprised them: the system with vortex waves was able to reconstruct images of complex objects using only one-eighth of the previous frequency bandwidth. For simple targets, there is a gain, but not as large; for distributed targets made of many small details, without vortices the picture did not come out at all. It is as if an artist, instead of a hundred different paints, took a dozen but applied each stroke at a new angle, and the canvas turned out no worse.

This approach could make radio imaging systems cheaper for security, medicine, and even archaeology. Instead of bulky scanners with a wide frequency band — a compact device with smart signal processing. The vortex helps see the invisible at lower cost.