Antennas used in Radars are often required to rotate to provide a 360 degree view of the surroundings. Traditionally this is achived by physically rotating the antennas to provide a complete view. Over time physically rotating antennas were related by phased array antennas. Phased array antennas are flat panels made up of miniature transmitters that each emit fractions of an overall signal - every fraction varied so that it all adds up to a single linear beam in a particular direction. The antennas can modulate the direction of that overall beam by altering the electronic properties of each individual signal source.
However, packing multiple small-scale antennas into one surface adds up to costly and colossal devices overall, limiting their usefulness. Rather than building a phased array from numerous individual antennas, a research team at the University of Wisconsin–Madison plans to create special reflective surfaces that achieve the same effect, but only rely on one single signal source. The team is headed by Nader Behdad and John Booske, professors at UW - Madison Electrical and Computer Engineering.
With support from a $1.1 million grant from the U.S. Office of Naval Research, the researchers are working out a new strategy to create antennas that spin their beams in circles while the devices stand still. They claim to have found a practical way to achieve beam-steering that the antennas field has largely overlooked for many years.
Much like the way in which the curved reflector in a car’s headlamp concentrates light emanating spherically outward from a single bulb into a forward beam, these flat arrays focus microwave signals into directed columns by altering the electronic properties of individual elements on their surfaces. But unlike mirrored dishes, these devices can vary the direction of the reflected beams by tuning individual elements on the surface.
Achieving that tuning, however, is no easy task. They tried numerous complicated approaches to modulate every component before they realized that they did not need to control each element one by one. Instead they harnessed small-scale mechanical motion within the entire antenna itself by making tiny adjustments to one large component, called the ground plane, that sits below the entire structure.
In order to do beam-steering, you don’t need to individually tune each element. A gradient needs to be created, which can be done by simply tilting the ground plane on one corner a little bit down and the other a little bit up. Small tilting motions inside an overall flat plane require much less time and mechanical force than spinning a large reflector dish.
To test the feasibility of this approach, the group made a low-cost prototype, which successfully provided proof of concept of electromagnetic principles. Now, the team is working to identify appropriate materials and techniques to improve this concept, making it suitable for real-world applications.
