Two scientists have created a thin, scalable and effective radar cloaking device which could be used to hide just about anything
Physicists have been experimenting with cloaking devices for a while now, but their experiments have usually been limited to single atoms and other, very small, objects. That time is over. Professor George Eleftheriades and PhD student Michael Selvanayagam from the S. Rogers Sr. Department of Electrical & Computer Engineering have invented a thin, scalable method for cloaking just about anything from radar detection.
It’s worth noting that this isn’t an invisibility cloak in the standard science-fiction sense of the word; the object can still be seen by the naked eye. However, for most cloaking applications, one could easily argue its more important to be invisible to a radar system, than to be actually invisible. Furthermore, since both visible light and radar are forms of electromagnetic waves, it’s not impossible to some day adapt the technology to the visible spectrum.
To understand how the cloak works, its necessary to understand how radar works. Picture a ship out on the open ocean. If you want to detect that ship using radar, your radar system emits electromagnetic waves in every direction. Where there is open ocean, the waves will just keep going, but when they encounter the ship, they bounce back and return to my radar system. When they return, I’ll know in what direction and distance the object is.
The cloaking device involves covering the ship, or indeed any object, in tiny antennas that radiate an electromagnetic field. The field effectively cancels out the incoming radar waves, meaning there’s nothing left that will bounce off the ship and return to the radar.
“We’ve demonstrated a different way of doing it,” says Eleftheriades. “It’s very simple: instead of surrounding what you’re trying to cloak with a thick metamaterial shell, we surround it with one layer of tiny antennas, and this layer radiates back a field that cancels the reflections from the object.”
The cloaking device
Eleftheriades experiment successfully cloaked a metal cylinder using a thin layer of loop antennas. He says that in the future, the technology might be printable and could then easily be applied to just about anything. At the moment, the antennas need to be attuned to a specific wavelength, but in the future, broader frequency ranges should be possible. He also states that while the obvious application is to hide military vehicles, it could just as easily be used in city infrastructure, to allow, say, mobile phone signals to pass through areas that were previously blocked.