Vector Backscattered Signals Improve Piggyback Modulation for Sensing With Passive UHF RFID Tags

We expand our “piggyback modulation” technique to integrate sensing functions with existing standard passive UHF RFID tags through wireless coupling. Instead of focusing on the scalar backscattered power that is proportional to the radar cross section (RCS), we exploit the vector backscattered signal with piggyback modulation. Measuring both amplitude and phase of the backscattered wave makes advanced demodulation possible. The measurement setup, experimental results, demodulation analysis, and numerical simulation for the conventional amplitude-shift keying (ASK) and quasi-4-quadrature amplitude modulation (quasi-4-QAM) are presented. Quasi-4-QAM demodulation reduces the interference between two independent data streams and improves the bit error rate for the same RF power. While we do not show explicit data from any given sensor, we do show that a generic sensor signal will be improved with our technique.

[1]  Huan-Yang Chen,et al.  Piggyback modulation for UHF RFID sensors , 2010, 2010 IEEE MTT-S International Microwave Symposium.

[2]  Daniel S. Yeung,et al.  A brief survey on current RFID applications , 2009, 2009 International Conference on Machine Learning and Cybernetics.

[3]  R. Bansal,et al.  Antenna theory; analysis and design , 1984, Proceedings of the IEEE.

[4]  Aggelos Bletsas,et al.  Improving Backscatter Radio Tag Efficiency , 2010, IEEE Transactions on Microwave Theory and Techniques.

[5]  K. V. S. Rao,et al.  Phase based spatial identification of UHF RFID tags , 2010, 2010 IEEE International Conference on RFID (IEEE RFID 2010).

[6]  Huan-Yang Chen,et al.  Vector backscattered signal analysis of piggyback modulation for passive UHF RFID Tags , 2011, 2011 IEEE MTT-S International Microwave Symposium.

[7]  Sergio Verdu,et al.  Multiuser Detection , 1998 .

[8]  Pavel Nikitin,et al.  Differential RCS of RFID tag , 2007 .

[9]  Zhihua Wang,et al.  System design considerations of highly-integrated UHF RFID reader transceiver RF front-end , 2008, 2008 9th International Conference on Solid-State and Integrated-Circuit Technology.

[10]  Matthew S. Reynolds,et al.  QAM backscatter for passive UHF RFID tags , 2010, 2010 IEEE International Conference on RFID (IEEE RFID 2010).

[11]  Huan-Yang Chen,et al.  Coupling sensors to UHF RFID tags , 2009, 2009 IEEE MTT-S International Microwave Workshop on Wireless Sensing, Local Positioning, and RFID.

[12]  S. Tedjini,et al.  On the measurement of the delta Radar Cross Section (ΔRCS) for UHF tags , 2009, 2009 IEEE International Conference on RFID.

[13]  D. van der Weide,et al.  Radar Cross-Section Analysis of Backscattering RFID Tags , 2007, IEEE Antennas and Wireless Propagation Letters.

[14]  Daniel M. Dobkin,et al.  The RF in RFID: Passive UHF RFID in Practice , 2007 .