Smart metasurfaces promise to double wireless network capacity

September 28, 2021 // By Rich Pell
Smart metasurfaces promise to double wireless network capacity
Researchers at the University of Toronto say they have found that reflectors made of metamaterials - materials engineered to have a property that is not found in naturally occurring materials - can channel electromagnetic waves to enable more wireless data to be transmitted over a single frequency.

This newly realized property, called "full-duplex nonreciprocity," say the researchers, could double the capacity of existing wireless networks.

"This is happening," says George Eleftheriades, a professor in the Edward S. Rogers Sr. department of electrical and computer engineering in the Faculty of Applied Science & Engineering. "Within the next three to five years this technology will be adopted."

Metamaterials are synthetic structures composed of building blocks that are smaller than the wavelengths they are designed to manipulate. The material used by the researchers is composed of repeating unit cells about 20 millimeters in size. These appear to form one homogenous object - a metasurface - for larger electromagnetic waves such as microwaves, which are used to carry cell phone signals and reflect off the metasurface exhibiting a property known as nonreciprocity.

An example to illustrate this using light is a car's rear-view mirror, say the researchers.

"When you're driving and look in the rear-view mirror, you see the driver behind you," says Eleftheriades. "That driver can also see you because light bounces off the mirror and follows the same path backwards. What's unusual about nonreciprocity is that the incident angle and the reflected angle are not equal. To be specific, the backward path for the wave is different. Basically, you can see someone, but you cannot be seen."

In addition, metasurfaces can be used to steer and amplify incoming beams, which is useful in many applications, from medical imaging and solar panels to satellite communications and even nascent cloaking technology. By adding the capability to steer the reflective beam, new intelligent metasurfaces could make a significant mark on wireless communication, say the researchers.

"In everyday experience, a microwave emitted from a tower reaches its intended terminal point, like a modem, and then goes back to the telecommunication station," says Eleftheriades. "That's why when you have a conversation on your cellphone, you do not talk and listen on the same channel.

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