Triple-Resonance Chipless RFID Tag With Dual Circularly-Polarized Wideband Reader Antenna for Wirelessly Differentiating Liquid

To wirelessly differentiate specified liquid samples, this article presents a radio-frequency identification (RFID) front-end including wideband reader antenna with chipless tag. The proposed reader antenna employs left-handed circularly-polarized (LHCP) antenna for transmitter (Tx) and right-handed circularly-polarized (RHCP) antenna for receiver (Rx), to improve the Tx-Rx isolation and also liberate the orientation and polarization of chipless tags. This dual circularly-polarized (dual-CP) configuration also features wide bandwidths of impedance and axial ratio, by using sequentially-rotated structure. Moreover, the proposed chipless tag has three resonances, among them, one independent resonance provides a lookup table for fast and easy identification, and another two resonances can be used to reconfirm the identification results. For validation, dual-CP reader antenna array and chipless tag are numerically optimized, experimentally measured, and also in-vivo demonstrated to wirelessly differentiate liquid samples.