A smart wall for cell phones and tablets

Most of our offices and homes reverberate with unseen microwaves that are emitted by a Wi-Fi box or other base station and, hopefully, interact with our wireless devices such as cell phones, laptops, and tablets. Sophisticated antennas in those devices help to capture the multiply scattered waves as they zip by (see the article by Steve Simon and coauthors, Physics Today, September 2001, page 38). Still, reception is often spotty at best. To optimize reception, Mathias Fink, Geoffroy Lerosey, and their colleagues at Institut Langevin in Paris are looking at the environment. Using ideas from time-reversal acoustics (see Fink’s article in Physics Today, March 1997, page 34) and spatial light modulators in optics, they engineered tunable metamaterial panels that focus wireless signals onto a wireless device, say a cell phone. Their prototype spatial microwave modulator (SMM) has 102 unit-cell “pixels,” each with two resonators and a...