UHF RFID Technologies for Identification and Traceability

3

The Backscattering Technique and its Application

Before starting …

Today backscattering and shunt regulator techniques in RFID are not new … but their mutual incidences are not very well known. So, to give to the reader a good and complete overview about this complex subject, a significant part of the content of this chapter is issued from the already existing Dominique Paret books: RFID en Ultra et Super Hautes Fréquences UHF-SHF: Théorie et mise en oeuvre, Dunod, 2005/2008, and the English version RFID at Ultra and Super High Frequencies: Theory and Application, John Wiley, 2009.

 

As shown in previous chapters, the power P_s reflected or reradiated by the tag (which is dependent on the value of the power flux density s) can be received and detected by the receiving antenna of the base station and can thus act as a signal informing the base station of whether or not an object or tag is present in the electromagnetic field.

Also, while the tag is illuminated, and regardless of whether it is remotely powered or locally battery assisted, provided that it has been designed to respond accurately via a specific modulation, it is called “backscattering modulation”, which will be described in detail later on.

Therefore, it is useful to analyze the way in which the radar cross section (RCS) is varied or modulated, and to define the extent of its variation – the quantity Δσ_{e s} – as a function of a possible coding and a specific modulation, which will enable us to determine its ability ...