Frequency Shift Coded microstrip shorted stub resonators for Chipless RFID tag applications

A passive high security chipless RFID tag designed using two shorted stub resonators is presented in this paper. The tag identity is encoded in the spectral domain using Frequency Shift Coding technique. 100 different code words are possible in 1.98 to 3.67 GHz band. Bistatic detection approach is used to decode the tag identity from either the amplitude or group delay information. The tag consists of two cross polarised wide band antennas integrated to shorted stub resonators, for transmission and reception of signals. The resonators are designed and fabricated on substrate C-MET LK4.3 of dielectric constant 4.3 and loss tangent 0.0018. Measured results on realized prototypes are provided to ensure the reliability of the proposed design.