Design of a novel antenna system intended for harmonic RFID tags in paper substrate

This paper presents the design of a novel compact dual-layer harmonic tag in paper substrate, based on a system of nested annular slot antennas. The passive tag is interrogated by a signal at f₀ = 1.2 GHz and the signal transmitted back to the reader is converted to 2f₀ = 2.4 GHz in order for the system to be immune to clutter returns. The frequency conversion is performed by a single Schottky diode frequency doubler, which shows a theoretical conversion loss of 13 dB at the output frequency of 2.4 GHz for an available input power of only -10 dBm. Additionally, a tapered annular slot antenna has been proposed so as to increase the operational bandwidth.