Radio waves have long surrounded us, with each new broadcast radio station or cellular tower adding to the electromagnetic (EM) haze. Most users take for granted that their wireless call will always go through, because of the reliability of their transmit networks. Unfortunately, a great deal of RF/microwave energy is lost to the environment in the process of making a cellular phone call but a design trend in developing energy-harvesting devices may prevent some of that waste sometime soon.

Electronics innovators such as Intel have demonstrated ways to extract low-power energy from these transmitted radio waves. The technology, based on using sensitive RF receivers to capture signals and then convert them to DC power, has been largely in the research stage for the better part of the last decade and may now be "ready for prime time." A growing number of companies are developing the RF integrated circuits (ICs), power converters, and power cells (batteries) needed to make energy harvesting a practical reality, and some of those efforts will be reported later this year in the pages of Microwaves & RF.