Design of a slotted chipless RFID humidity sensor tag

This paper proposes a chipless Radio-Frequency Identification (RFID) sensor tag for low-cost and long-term humidity monitoring. The slotted scatterer structure are fabricated on FR4 substrate by grooving etching. The encoding unit stores the ID information by the combination of the different length slots. Si nanowires are deposited on the surface of the slots to form the sensing unit. Based on the principle of radar electromagnetic backscattering, the test system measures the transmission coefficient curve to obtain the ID and humidity information of the tag. The test results show that the proposed chipless sensor tag achieves good hysteresis and consistence performances and the maximum error is not exceed 10%.