Creating Fixed Antennas For Beam Steering

By Jof Enriquez,
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University of Wisconsin–Madison electrical engineers have devised a new antenna design that allows transmission of radiofrequency signals in multiple directions by a stationary antenna with no rotating parts.

Conventional antennas rotate on top of a fixed platform and require time and mechanical energy to perform a full sweep. This set-up presents constraints in responding to threats. As a solution, researchers have been trying to redirect radar beams using phased arrays consisting of many radiating elements on a flat surface. A phase shifter in each element steers the beams in the desired direction. However, these antennas are costly to build.

Instead of building a phased array, electrical engineers at University of Wisconsin–Madison developed special reflective flat surfaces that achieve the same effect, but only rely on a single signal source.

“Up until this idea there was practically no way to meet the almost impossible specification of the ideal solution,” says John Booske, UW–Madison electrical and computer engineering professor, in a news release.

The flat arrays alter the electronic properties of individual elements on their surfaces to convert spherical radio signals into single-column beams. Unlike mirrored dishes, these arrays can vary the direction of the reflected beams by tuning individual elements on the surface.

The researchers later discovered that they need not tune all individual elements to control the beams. Instead, they found that slightly tilting the ground plane component of the device to opposite corners achieves the same effect.

“Our approach doesn’t depend on exotic materials that bend the laws of physics,” says Nader Behdad, principal investigator on the project and UW–Madison professor of electrical and computer engineering. “We’ve found a practical way to achieve beam-steering that the antennas field has largely overlooked for many years.”

The UW-Madison team has received a $1.1 million grant from the U.S. Office of Naval Research to develop their design, for which a patent has been filed with the assistance of the Wisconsin Alumni Research Foundation.

Behdad and colleagues have been working hard to improve on existing antenna technology. His team is also developing compact antennas for transmitting jamming signals in an electronic attack, and designing "coupling structures" to make military vehicles act as antennas themselves.