Passive UHF tag-to-tag communications properties

The UHF passive Radio Frequency Identification technology generally enables an asymmetric interaction between the reader and the tag, the latter only being able to respond to the query of the reader through backscattering modulation. Very recently some experiments put into evidence the possibility to set up a tag to tag communication by using a simple illuminator. The key issues and the physical limitation of such a cross-link are here investigated both theoretically and numerically by fully accounting for the mutual coupling among the tags, their radiation properties and the impedance modulation.