Chipless radio frequency identification devices ("rfid")

Chipless RFID tag comprising:

• a dielectric substrate on which a pattern or patterns are mounted composed of a layer of conductive material, wherein the dielectric substrate has a relative permittivity measured at any frequency between 3 and 10 GHz of between 1 and 2 and a loss tangent value measured at any frequency between 3 and 10 GHz of less than 10−3.