A new approach to invisibility cloaking from researchers at the University of Toronto, Canada has yielded an adaptable system capable of shielding objects of various sizes from radar detection.
Developed by professor George Eleftheriades and Ph.D. student Michael Selvanayagam of The Edward S. Rogers Sr. Department of Electrical & Computer Engineering, the cloaking system utilizes a single layer of small loop antennas that collectively radiate an electromagnetic field to cancel out any radio waves that bounce off the object, effectively hiding it from the radar. Their paper, “Experimental Demonstration of Active Electromagnetic Cloaking” appeared this month in the journal Physical Review X.
According to Eleftheriades, the new development is a step up from previous cloaking systems, which were made using layers of metamaterials and were especially large and bulky when used to cloak bigger objects, such as a car.
“We’ve demonstrated a different way of doing it,” he said. “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.”
In a demonstration, the researchers successfully cloaked a metal cylinder from radio waves using a series of loop antennas. The scalable system can cloak larger objects with the addition of more loops, and Eleftheriades says the loops could become printed and flat.
While the antenna loops currently must be manually attuned to the electromagnetic frequency they need to cancel, the researchers say eventually they could function both as sensors and active antennas, adjusting to different waves in real time in a method similar to that of noise-cancelling headphones.
The cloaking technology could be used in a variety of applications, such as hiding military vehicles or cloaking structures that interrupt signals from cellular base stations to allow the transmissions to pass by freely. The system can also alter the signature of a cloaked object to make it appear larger, smaller or at a slightly different position.
“We’ve taken an electrical engineering approach, but that’s what we are excited about,” Eleftheriades said. “It’s very practical.”
