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Zero power radio recievers based on SAW correlators. - Adventures in Engineering — LiveJournal
The wanderings of a modern ronin.

Ben Cantrick
  Date: 2006-07-27 01:14
  Subject:   Zero power radio recievers based on SAW correlators.
Public
  Mood:der uber-nerd

This report describes both a general methodology and some specific examples of passive radio receivers. A passive radio receiver uses no direct electrical power but makes sole use of the power available in the radio spectrum. These radio receivers are suitable as low data-rate receivers or passive alerting devices for standard, high power radio receivers. Some zero-power radio architectures exhibit significant improvements in range with the addition of very low power amplifiers or signal processing electronics. These ultra-low power radios are also discussed and compared to the purely zero-power approaches.

http://www.sandia.gov/mstc/products/usystemsprod/rfandoptosystems/saw.html

http://www.sandia.gov/mstc/documents/saw3.pdf


This is *exactly* what we need at work right now. A way for the master unit to tell all the field units to "wake up" and prepare for incoming transmission. And it uses zero battery power. Even some of the powered designs only use microwatts of power, which you can easily get from entirely passive devices like a solar panel or a thermocouple.

Neat shit.
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  User: nickhalfasleep
  Date: 2006-07-27 02:47 (UTC)
  Subject:   (no subject)
neat. RFID chips do something similar, being completely powered by incoming radio waves.
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Jon
  User: j_b
  Date: 2006-07-27 03:44 (UTC)
  Subject:   (no subject)
...he said to the guy who worked X years in RFID ;-)
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Ben Cantrick
  User: mackys
  Date: 2006-07-27 04:02 (UTC)
  Subject:   (no subject)
You generally have to get them within 15 feet of the transmitter, though. The circuits passive RFID tags use to extract energy from the radio waves are not terribly efficient and the RF has to be pretty strong to run them.

The Sandia design will generate an output spike even when the RF field strength is in the tens of millivolts.
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