title: Design of a Humidity Sensor Tag for Passive Wireless Applications.
abstract: This paper presents a wireless humidity sensor tag for low-cost and low-power applications. The proposed humidity sensor tag, based on radio frequency identification (RFID) technology, was fabricated in a standard 0.18 μm complementary metal oxide semiconductor (CMOS) process. The top metal layer was deposited to form the interdigitated electrodes, which were then filled with polyimide as the humidity sensing layer. A two-stage rectifier adopts a dynamic bias-voltage generator to boost the effective gate-source voltage of the switches in differential-drive architecture, resulting in a flat power conversion efficiency curve. The capacitive sensor interface, based on phase-locked loop (PLL) theory, employs a simple architecture and can work with 0.5 V supply voltage. The measurement results show that humidity sensor tag achieves excellent linearity, hysteresis and stability performance. The total power-dissipation of the sensor tag is 2.5 μW, resulting in a maximum operating distance of 23 m under 4 W of radiation power of the RFID reader.
authors.affiliation: School of Electrical and Electronic Engineering, East China JiaoTong University, Nanchang 330013, China. zgxiangyu@ecjtu.edu.cn.
authors.forename: Xiang
authors.initials: X
authors.lastname: Wu
authors.affiliation: School of Electrical and Electronic Engineering, East China JiaoTong University, Nanchang 330013, China. Dengfangming@ecjtu.edu.cn.
authors.forename: Fangming
authors.initials: F
authors.lastname: Deng
authors.affiliation: School of Mechatronic Engineering, East China JiaoTong University, Nanchang 330013, China. haoyong@ecjtu.edu.cn.
authors.forename: Yong
authors.initials: Y
authors.lastname: Hao
authors.affiliation: School of Electrical and Electronic Engineering, East China JiaoTong University, Nanchang 330013, China. daiwei@ecjtu.edu.cn.
authors.forename: Zhihui
authors.initials: Z
authors.lastname: Fu
authors.affiliation: School of Electrical and Electronic Engineering, East China JiaoTong University, Nanchang 330013, China. lhzhang@ecjtu.edu.cn.
authors.forename: Lihua
authors.initials: L
authors.lastname: Zhang
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation*; D004566:Electrodes; D004867:Equipment Design; D006801:Humans; D006813:Humidity; D057233:Radio Frequency Identification Device; D012666:Semiconductors; D012680:Sensitivity and Specificity; D059015:Wireless Technology / Q000295:instrumentation*
keywords: complementary metal oxide semiconductor (CMOS); humidity sensor; radio frequency identification (RFID); rectifier; sensor interface