TY - JOUR
T1 - A Low-Power, Wireless, Capacitive Sensing Frontend Based on a Self-Oscillating Inductive Link
AU - Schormans, Matthew
AU - Valente, Virgilio
AU - Demosthenous, Andreas
PY - 2018
Y1 - 2018
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 μm 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.
AB - 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 μm 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.
KW - Capacitance
KW - Capacitive sensing
KW - humidity sensing
KW - Impedance
KW - inductive link
KW - Monitoring
KW - Resonant frequency
KW - Sensors
KW - Wireless communication
KW - wireless sensing.
KW - Wireless sensor networks
UR - http://www.scopus.com/inward/record.url?scp=85049838434&partnerID=8YFLogxK
UR - http://resolver.tudelft.nl/uuid:ac4b641a-b515-4441-a475-a035e03f0a51
U2 - 10.1109/TCSI.2018.2835148
DO - 10.1109/TCSI.2018.2835148
M3 - Article
AN - SCOPUS:85049838434
SN - 1549-8328
VL - 65
SP - 2645
EP - 2656
JO - IEEE Transactions on Circuits and Systems I: Regular Papers
JF - IEEE Transactions on Circuits and Systems I: Regular Papers
IS - 9
ER -