Passive RFID sensors

confidencehandElectronics - Devices

Nov 27, 2013 (4 years and 6 months ago)


Passive RFID sensors

Michael Helmeste

Mentor: Mark Bachman

August 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 t
ags 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
MS 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 chan
ge 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 an
d 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.