Rectennas

摘要

What are they? Rectifying antennas, which convert electromagnetic energy (such as radio waves) into direct current (DC) electricity. They were invented in 1964 by US engineer William C Brown, who demonstrated the technology by powering a model helicopter using microwaves transmitted from the ground. This method has been proposed as a way to power military drones from the ground, but a recent breakthrough could see rectennas also being used to charge phones, laptops and other gadgets. It involves technology described as an "electronic tablecloth".