Group-delay modulation with metamaterial-inspired coding particles for passive chipless RFID

Significant progress has happened to the research field of passive chipless RFID since it is beneficial in various applications but in terms of encodable information content it lags far behind the chip-based counterparts. Novel approaches tend to implement higher-order modulation to overcome this situation. This work presents a straight forward approach for implementing a reliable higher-order modulation scheme, thus to increase the information content. It is based on a frequency domain on-off-keying backscatter modulation scheme with extremely small resonators, where additional information, the resonator's group delay, is added to the on-states within this novel group-delay modulation scheme. Between different IDs, the group delay is varied by changing the resonator's loaded quality factor without introducing additional losses. Beside showing the working principle, prototype measurements proof the concept by realizing a two-symbol wireless identification.