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Correction published on 22 July 2014, see Sensors 2014, 14(7), 13171-13172.

Sensors 2014, 14(5), 8728-8739; doi:10.3390/s140508728

A CMOS Humidity Sensor for Passive RFID Sensing Applications

1,2,* , 1
1 School of Electrical Engineering and Automation, Hefei University of Technology, Hefei 230009, China 2 School of Electrical and Electronic Engineering, East China JiaoTong University, Nanchang 330013, China
* Author to whom correspondence should be addressed.
Received: 23 February 2014 / Revised: 24 April 2014 / Accepted: 8 May 2014 / Published: 16 May 2014
(This article belongs to the Special Issue Polymeric Micro Sensors and Actuators)
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This paper presents a low-cost low-power CMOS humidity sensor for passive RFID sensing applications. The humidity sensing element is implemented in standard CMOS technology without any further post-processing, which results in low fabrication costs. The interface of this humidity sensor employs a PLL-based architecture transferring sensor signal processing from the voltage domain to the frequency domain. Therefore this architecture allows the use of a fully digital circuit, which can operate on ultra-low supply voltage and thus achieves low-power consumption. The proposed humidity sensor has been fabricated in the TSMC 0.18 μm CMOS process. The measurements show this humidity sensor exhibits excellent linearity and stability within the relative humidity range. The sensor interface circuit consumes only 1.05 µW at 0.5 V supply voltage and reduces it at least by an order of magnitude compared to previous designs.
Keywords: RFID technology; passive RFID tag; humidity sensor; interface circuit; phase-locked loop; CMOS technology RFID technology; passive RFID tag; humidity sensor; interface circuit; phase-locked loop; CMOS technology
This is an open access article distributed under the Creative Commons Attribution License (CC BY) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Deng, F.; He, Y.; Zhang, C.; Feng, W. A CMOS Humidity Sensor for Passive RFID Sensing Applications. Sensors 2014, 14, 8728-8739.

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