Chipless RFID tag based on metamaterial absorbers

A metamaterial absorber used as RFID tag is proposed in this paper. Absorbers lead to small tags with absorption peaks as characteristic signatures. The designed structure is a metasurface with metallic frequency selective surfaces over a grounded dielectric slab. CST simulations have absorption peaks of 99.25% at 3.5 GHz and 99.4% at 5.9 GHz. Absorber unit cell on FR-4 is a square of dimensions of 0.201 times the wavelength at the low resonant frequency. Simulated radar cross section presents adequate beamwidth for the designed frequency bands.