'Invisibility cloak' makes objects undetectable by radar

(UPI) -- Engineers at the University of Toronto have developed a functional "invisibility cloak" that can be used to make different objects invisible to radar.

By surrounding an object with small antennas that collectively radiate a electromagnetic field, it will radiate radio waves that cancel out waves bouncing off the object, thereby rendering the object invisible to radar.

"We've taken an electrical engineering approach, but that's what we are excited about," said George Eleftheriades, an engineering professor at the University of Toronto. "It's very practical."

For their experiment, researchers cloaked a metal cylinder wrapped in a layer of tiny loop antennas. At present the loop antennas emit a known electromagnetic frequency, but can be tuned to automatically change based on the frequency of the waves hitting the object. The researchers hope to scale this technology for larger objects.

The technology has obvious military uses but researchers say it can also be used to cloak structures that block cellphone signals from passing through. By cloaking the structure with tiny antennas it will let the signals pass freely.

The system does not make an object invisible from human sight but only tricks a radar into believing that the object is not present. While invisibility has remained in the domain of science fiction and fantasy, scientists now believe that invisibility is increasingly possible.

"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," Eleftheriades said.