Nokia Develops Phone that Draws Power from Radio Frequency

Nokia has set out to change the face of communication when it announced that it is developing a device that can harvest up to 50 milliwatts of power from ambient radio frequencies for recharging a cell phone.
This technology could draw enough power from ambient electromagnetic radiation waves to keep a cell-phone handset topped up. Wi-Fi transmitters, cell-phone antennas, TV masts, and other emit these
waves. It will require a wideband receiver capable of capturing signals from between 500 megahertz and 10 gigahertz.
According to the information made available by Nokia, device will work on the same principles as a crystal radio set or radio frequency identification (RFID) tag: by converting electromagnetic waves into an
electrical signal. This requires two passive circuits. As put by Markku Rouvala, a researcher from the Nokia Research Centre, in Cambridge, “Even if you are only getting microwatts, you can still harvest energy, provided your circuit is not using more power than it’s receiving.”
He also said that, to increase the amount of power that can be harvested and the range at which it works, Nokia is focusing on harvesting many different frequencies. “It needs a wideband receiver,” says Rouvala, to capture signals from between 500 megahertz and 10 gigahertz–a range that encompasses many different radio communication signals.
Developers use the same principles as a crystal radio set or radio frequency identification (RFID) tag. They convert electromagnetic waves into an electrical signal. Ultimately, Nokia plans to use the technology in conjunction with other energy-harvesting approaches, such as solar cells embedded into the outer casing of the handset.
In a similar development, Joshua Smith at Intel and Alanson Sample at the University of Washington, in Seattle, ealier this year developed a temperature-and-humidity sensor that draws its power from the signal
emitted by a 1.0-megawatt TV antenna 4.1 kilometers away. This only involved generating 60 microwatts, However, Smith says that 50 milliwatts could require around 1,000 strong signals and that an antenna capable of picking up such a wide range of frequencies would cause efficiency losses along the way.