sábado, 20 de marzo de 2010

Passive RFID sensors

Passive RFID sensors
Michael HelmesteMentor: Mark BachmanAugust 26, 2005
Passive RFID technologies are becoming increasingly commonplace and inexpensive. Used in the supply chain for inventory tracking and management, the potential for value added RFID tags with passive sensors is enormous. By integrating MEMS sensor technology with RFID tags, the existing infrastructure of RFID can be utilized to passively acquire environmental data. Ideally, sensors would be integrated with the digital logic of the RFID chips themselves. However, existing solutions are not ready for mass production, and the key selling point of RFID is low cost. Elegant, low cost solutions result from modifying the configuration of the tag's antenna, and can easily be manufactured. RF MEMS switches are used in the modification of the tag's antenna to provide ancillary data. Two solutions of modifying the tag were investigated. One solution involves using the activation of a sensor to modify the tag's resonant frequency, detected by a change in reflected power at the reader. The reader must be modified to emit two carriers. The other solution involves a simple encoding scheme using two RFID tags, where only one tag is connected to a sensor. The two carrier solution is technically complex and requires modifications to the reader, the price of which is high to begin with. The two tag solution results in a higher per unit cost, but requires no modification of the reader and can be easily integrated with existing infrastructure.

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