rectenna

A new gadget can turn WiFi signals into electricity. It could one day mean an end to charging phone batteries, though the power levels mean medical uses might be more realistic. The device is a new variant of a "rectenna," which is short for ... rectifying antenna. Traditionally it turns electromagnetic energy into direct current electricity. Although the rectenna was developed more than 50 years ago, it's not been widely used. At the moment the most common use is in contactless cards, where a wireless signal from a card reader can not only open communications, but provide just enough ... (view more)