DOI: 10.1109/TMTT.2023.3305152   IEEEXPlore: https://ieeexplore.ieee.org/document/10227356

Multistate (M-S) chipless radio-frequency identification (RFID) with a resonant scatterer trapped between dissimilar dielectric layers.

4.27 GHz resonance for this particular RFID tag; 4.5 to 5.0 GHz TX/RX

The resonant frequency of the scatterer changes as it moves in the near field between the two dissimilar dielectric layers and translates into a significant variation in the scattering response of the tag at the two extremes of motion.

Human vital sign monitoring; mechanical fault monitoring.

Submillimeter vibration of 0.48 mm sensed at 2.5 m with an intermediate 15 cm wall between the tag and the transceiver. 45x improvement in differential radar cross section (RCS), 2.5x improvement in read range compared to superior doppler applications. 25x compared single-state (S-S) tags where only the fundamental frequency is detectable (compared to up to 8 detectable harmonics for the M-S tag).