In this paper, a new method of data encoding is presented to increase the number of coded bits in a chipless RF identification (chipless RFID) tag. To achieve this purpose, different values of an equation between the phase of scattering parameters (S-parameters) at a certain frequency are considered as different coded bits. In this proposed tag, a transition zero is produced by the spiral resonator. The different phases of S parameters created by different coupling positions of the spiral resonator are considered as coded bits at the frequency of transition zero (carrier frequency). The chipless RFID tags are designed at 1.7 GHz with five different states and the measurement results are in good agreement with the EM simulation results.
