A Chipless RFID Based on Multiresonant High-Impedance Surfaces

A novel chipless RF identification based on a multiresonant high-impedance surface is proposed. The structure is based on a finite metallic frequency-selective surface (FSS) comprising 2 × 2 (30 mm × 30 mm) or 3 × 3 (45 mm × 45 mm) unit cells. The FSS unit cell is formed by several concentric square loop resonators. The thin structure performs deep absorptions of the impinging signal at several resonant frequencies related to the loop resonators. If one of the printed loops in the unit cell is removed, the corresponding absorption peak disappears from the reflected signal giving the possibility of encoding a desired bit sequence. The proposed structure exhibits some intrinsic advantages, such as scalability (bit number increase) without any size increase, polarization independence, large read range, and the capability of operating when mounted on metallic objects. A transmission line model is employed to illustrate the operation principle of the structure, whereas measurements on realized prototypes are provided to assess the reliability and effectiveness of the proposed design.