In some embodiments, surface acoustic wave devices (SAW) are also used. Sandia National Laboratories has developed the Zero-Power Receiver, an unpowered signal receiver that detects and responds to very weak signals using pyroelectric devices as impedance transformers and/or demodulators. A long-range, zero-power radio receiver with sufficient sensitivity would greatly extend battery life in wireless mobile applications. Similarly, global positioning system (GPS) receivers cycle their receivers on and quickly off to keep track of changes in location. Right now, cellphones continually turn their radio receiver circuitry on and off to listen for attempts to be contacted by the cellular base station. Such a radio receiver could solve a number of communication-related problems. A passive, or zero-power, radio receiver uses no direct electrical power, but makes sole use of the power available from a transmitter via the radio spectrum.Ĭommercial applications for short-range, zero-power radio receivers are already common for RFID tags used in applications ranging from low-cost theft prevention devices in stores and libraries, to somewhat more expensive devices used to track shipping containers and pallets in warehouses.Ī long-range, truly zero-power radio receiver has until now been unavailable. There are longrange, low-powered tags that draw energy either from a battery or some other form of localized power. Currently, most unpowered wireless RFID tags only have a range of a few meters. There are several different types of wireless radio frequency identification (RFID) tags that are truly zero-power radios. Sandia National Laboratories, Albuquerque, New Mexico
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