A novel compact harmonic RFID sensor in paper substrate based on a variable attenuator and nested antennas

This paper presents the design of a novel chipless harmonic RFID sensor in paper substrate based on a variable attenuator implemented as a π resistive network, which drives a single Schottky diode frequency doubler and a system of nested tapered annular slot antennas. The passive tag is interrogated by a signal at f
₀
= 1.2 GHz and the signal transmitted back to the reader is converted to 2f
₀
= 2.4 GHz in order for the system to be immune to clutter returns. The sensor information is encoded in the magnitude of the re-transmitted signal and a dynamic range around 20 dB is experimentally demonstrated.