Wireless Humidity Sensing with Chipless Radio Frequency Identification Tag
Bo Wang, Junqiang He, Yalun Song, Ke Wang, Shengli Cao · Sensors and Materials · 2024
In this study, a compact and flexible chipless radio frequency identification humidity sensor with dimensions of 21 × 21 mm 2 is realized.The resonator structure consists of a square open ring and a U-shaped ring on a Rogers TMM 4(tm) substrate.The Kapton relative permittivity is very sensitive to changes in ambient humidity, and the sensor is capable of detecting humidity when the resonator is covered with a Kapton film.The amplitude of the radar scattering cross section increases monotonically from -65.66 to -58.14 dB with an offset of 7.52 dB when the relative humidity (RH) increases from 40 to 90%.The chipless sensor designed in this study has a compact size of only 21 × 21 mm 2 with good resonance characteristics, and with the Kapton thin film covering, the sensor exhibits an excellent sensitivity of 0.15 dB/% RH.It also has a wide humidity measurement range from 40 to 90%.