Researchers are reinventing the mirror, at least for microwaves, potentially replacing the familiar 3D dishes and microwave horns seen on rooftops and cell towers with flat panels that are compact, versatile, and better adapted for modern communication technologies. The new reflectors offer lightweight, low-profile alternatives to conventional antennas. The panels could be easily incorporated onto surfaces of buildings or terrestrial vehicles.
Most reflectors are reciprocal: in the case of a bathroom mirror, for example, if you can see someone reflected in it, they can see you, too. The new reflector design breaks reciprocity, effectively turning it into a one-way mirror.
The flat-panel reflector can be controlled electronically, which means its characteristics can be reconfigured on the fly. This opens the window for beam steering, customized focusing, and other functions that are difficult to achieve with conventional antenna designs. Miniaturized versions could improve chip-based circuitry by ensuring that signals go only to the intended components and don’t lead to inadvertent signals in other parts of the circuit — a problem that chip designers often have to worry about.
The reflectors are composed of an array of finely structured electronic components on a planar surface. Applying signals to the components allows the 2D reflector to perform much like a 3D antenna, and in some cases, do things no conventional antenna could do. This sort of a device is known as a “metasurface” because its characteristics can be electronically changed to act in different ways without modifying the physical shape of the surface.
By applying electrical signals to the reflector components, the researchers modulated the metasurface to control the direction and frequency of reflected light. The nonreciprocal response of the reflector can help prevent antennas from picking up echoes from their outgoing broadcasts and protect delicate circuitry from powerful, potentially damaging incoming signals.
The new reflector platform opens opportunities in various applications including adaptive optics that can account for distortions that disrupt signals, oneway wireless transmission, and novel antenna designs.