TY  - JOUR
EP  - 2656
N2  - Wireless sensing systems are becoming popular in a range of applications, particularly in the case of biomedical circuits and food monitoring systems. A typical wireless sensing system, however, may require considerable complexity to perform the necessary analog to digital conversion and subsequent wireless transmission. Alternatively, in the case of inductive link based systems, large, manually operated impedance analyzers are required. Based on a detailed analysis of the link impedance, this paper proposes a simple method for wireless capacitive sensing through an inductive link that uses a self-oscillator and a frequency counter. The method enables changes in capacitance to be sensed and wirelessly transmitted simultaneously. In order to test the effectiveness of the method, a self-oscillating circuit was designed and fabricated in 0.18 ?m CMOS, and combined with an on-chip humidity sensing capacitor. The system was tested in a humidity chamber across a range of 20-90%rh. Measured results from the system demonstrate that capacitive changes as small as 28 fF, translating to <2%rh, can be resolved, with a power consumption of 1.44 mW.
UR  - https://doi.org/10.1109/TCSI.2018.2835148
VL  - 65
A1  - Schormans, M
A1  - Valente, V
A1  - Demosthenous, A
ID  - discovery10053473
N1  - © 2018 IEEE. This work is licensed under a Creative Commons Attribution 3.0 License (https://creativecommons.org/licenses/by/3.0/).
Y1  - 2018/07/10/
TI  - A Low-Power, Wireless, Capacitive Sensing Frontend Based on a Self-Oscillating Inductive Link
AV  - public
JF  - IEEE Transactions on Circuits and Systems I: Regular Papers
IS  - 9
KW  - Sensors
KW  -  Resonant frequency
KW  -  Wireless sensor networks
KW  -  Wireless communication
KW  -  Impedance
KW  -  Capacitance
KW  -  Monitoring
SP  - 2645
SN  - 1549-8328
ER  -