Chipless RFID trasponders by using multi-resonant High-Impedance Surfaces

Multi-resonant metamaterial absorbers based on High-Impedance Surfaces (HIS) are proposed to be employed as a trasponder for Radio Frequency IDentifcation (RFID). The HIS comprises a Frequency Selective Surface (FSS) whose unit cell is formed by several concentric loop resonators. Every absorption peak of the reflection coefficient is associated to one of the concentric loop elements of the FSS and every peak can be removed or not depending on the presence of the corresponding loop. This allows to encode a bit sequence in the spectral response of the scattered field. The periodic structure is truncated to a 2x2 (30 mm x 30 mm) or 3x3 (45 mm X 45 mm) array for obtaining a compact device. The proposed configuration exhibits some intrinsic advantages with respect to already proposed chipless tags such as the possibility of increase the number of bits without any size increase, polarization independence and the capability of operating when mounted on metallic objects.