Transmit Diversity for Backscatter RFID

Project Members

Chenming Zhou (Disney Research Pittsburgh)
Azhar Hasan (Georgia Institute of Technology)
Joshua Griffin (Disney Research Pittsburgh)

The experimental setup used to measure backscatter transmit diversity with monostatic readers at 5.8 GHz. The four reader patch antennas are located on the table and the tag was moved over a grid using the 2D linear positioner.

Measurements showing the difference in power delivered to the RF tag with and without transmit diversity applied. The tag was moved along the X Path and Y Path shown by the dashed yellow lines (see the figure to the left).

The read range of passive, backscatter radio frequency (RF) tags is limited by the power delivered to the RF tag’s integrated circuit. This project seeks to increase the power delivered to passive backscatter RF tags using transmit diversity – a method that uses multiple antennas and channel knowledge to deliver power to the tag. By adjusting the phase of the signal transmitted from each reader antenna to cancel the phase delay of the channel, the signals from each antenna add constructively at the RF tag; hence, the power delivered to the RF tag is maximized. This technology can improve the read range and reliability for radio frequency RF tags in applications with time-varying channels — e.g., backscatter sensors operating near moving people or where radio frequency identification (RFID) tags cannot be confined to a portal.

Publications

The Phase Difference Method for Transmit Diversity in Monostatic RFID Systems-Thumbnail

The Phase Difference Method for Transmit Diversity in Monostatic RFID Systems
July 8, 2012
IEEE Antennas and Propagation Symposium 2012
Paper File [pdf, 867.64 KB]

Experimental Demonstration of Transmit Diversity for Passive Backscatter RFID Systems-Thumbnail

Experimental Demonstration of Transmit Diversity for Passive Backscatter RFID Systems
September 15, 2011
IEEE International Conference on RFID Technology and Applications (RFID-TA) 2011
Paper File [pdf, 1.13 MB]

Transmit Diversity for Backscatter RFID- Preliminary Results-Thumbnail

Transmit Diversity for Backscatter RFID: Preliminary Results
April 12, 2011
IEEE International Conference on RFID 2011
Paper File [pdf, 40.62 KB]

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