Experimental results with two wireless power transfer systems

A paper on the TechOnline website describes two systems that harvest power from a radio signal. In both cases the energy transfered is tiny but can be suffcient for a low power sensor.

The paper describes two wireless power transfer systems. The Wireless Identification and Sensing Platform (WISP) is a platform for sensing and computation that is powered and read by a commercial off-the-shelf UHF 915 MHz RFID reader that transmits 4 watts EIRP. WISPs are small sensor devices that consume in the order of 2uW to 2mW, and can be operated at distances of up to several meters from the reader.

The second system harvests VHF or UHF energy from TV towers, with power available depending on range and broadcast transmit power. An experiment is described in which 60uW is harvested at a range of about 4km and used to power a commercially available thermometer/hygrometer with LCD display.

The paper titled 'Experimental Results with two Wireless Power Transfer Systems' can be downloaded from
http://www.techonline.com/learning/techpaper/212902041 but you do need to fill some words into the online registration form to get it.

Tech Online
http://www.techonline.com/