Chipless RFIDs for metallic objects by using cross polarization encoding

This communication aims to demonstrate both theoretically and experimentally that chipless tags can be efficiently detected on metallic platforms by exploiting cross-polar reflection. The employed tag consists of a frequency selective surface (FSS) comprising concentric square loop resonators printed on a grounded dielectric slab. The co-polar reflection amplitude of the proposed structure is characterized by deep minima in correspondence of every resonance, whereas the cross-polar component of the reflection coefficient exhibits well defined frequency selective maxima. Since each resonance is determined by a specific concentric loop, the presence or the absence of a loop is used to apply an amplitude modulation on the reflected signal. Measurements on realized prototypes are also provided to assess the effectiveness of the proposed technique.