TY - JOUR
T1 - A Low-Power Impedance-to-Frequency Converter for Frequency-Multiplexed Wearable Sensors
AU - Li, Weilun
AU - Zhao, Junyi
AU - Wang, Yong
AU - Wang, Chuan
AU - Chakrabartty, Shantanu
N1 - Publisher Copyright:
© 2007-2012 IEEE.
PY - 2024
Y1 - 2024
N2 - We propose a low-power impedance-to-frequency (I-to-F) converter for wearable transducers that change both its resistance and capacitance in response to mechanical deformation or changes in ambient pressure. At the core of the proposed I-to-F converter is a fixed-point circuit comprising of a voltage-controlled relaxation oscillator and a proportional-to-temperature (PTAT) current reference that locks the oscillation frequency according to the impedance of the transducer. Using both analytical and measurement results we show that the operation of the proposed I-to-F converter is well matched to a specific class of sponge mechanical transducer where the system can achieve higher sensitivity when compared to a simple resistance measurement techniques. Furthermore, the oscillation frequency of the converter can be programmed to ensure that multiple transducer and I-to-F converters can communicate simultaneously over a shared channel (physical wire or virtual wireless channel) using frequency-division multiplexing. Measured results from proof-of-concept prototypes show an impedance sensitivity of 19.66, at 1.1,k load impedance magnitude and a current consumption of 128 μ A. As a demonstration we show the application of the I-to-F converter for human gesture recognition and for radial pulse sensing.
AB - We propose a low-power impedance-to-frequency (I-to-F) converter for wearable transducers that change both its resistance and capacitance in response to mechanical deformation or changes in ambient pressure. At the core of the proposed I-to-F converter is a fixed-point circuit comprising of a voltage-controlled relaxation oscillator and a proportional-to-temperature (PTAT) current reference that locks the oscillation frequency according to the impedance of the transducer. Using both analytical and measurement results we show that the operation of the proposed I-to-F converter is well matched to a specific class of sponge mechanical transducer where the system can achieve higher sensitivity when compared to a simple resistance measurement techniques. Furthermore, the oscillation frequency of the converter can be programmed to ensure that multiple transducer and I-to-F converters can communicate simultaneously over a shared channel (physical wire or virtual wireless channel) using frequency-division multiplexing. Measured results from proof-of-concept prototypes show an impedance sensitivity of 19.66, at 1.1,k load impedance magnitude and a current consumption of 128 μ A. As a demonstration we show the application of the I-to-F converter for human gesture recognition and for radial pulse sensing.
KW - Impedance-to-frequency converter
KW - frequency multiplexing
KW - multi-modal sensors
KW - strain gauge sensor
KW - wearable sensor
UR - http://www.scopus.com/inward/record.url?scp=85184818669&partnerID=8YFLogxK
U2 - 10.1109/TBCAS.2024.3362329
DO - 10.1109/TBCAS.2024.3362329
M3 - Article
C2 - 38319775
AN - SCOPUS:85184818669
SN - 1932-4545
VL - 18
SP - 885
EP - 895
JO - IEEE Transactions on Biomedical Circuits and Systems
JF - IEEE Transactions on Biomedical Circuits and Systems
IS - 4
ER -