A Low-Power Single-Path Bio-Impedance Measurement System Using an Analog-to-Digital Converter for I/Q Demodulation

In this paper, a low power single-path bio-impedance (Bio-Z) measurement system for early detection of acute myocardial ischemia is presented. The fully integrated system consists of a current source, an amplifier, and an analog-to-digital converter (ADC). The system utilizes the in-phase and quadra...

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Bibliographic Details
Published in:IEEE transactions on biomedical circuits and systems 2022-12, Vol.16 (6), p.1-10
Main Authors: Rezaee-Dehsorkh, Hamidreza, Ravanshad, Nassim, Shamsaki, Ali, Fakour, Maryam Rouhbakhsh, Aliparast, Peiman
Format: Article
Language:English
Subjects:
Amplifiers
Amplifiers, Electronic
Analog to digital converters
bio-impedance
capacitively-coupled
Circuits
Clocks
Current measurement
Current sources
Demodulation
Digitization
Digitizing
Electric Impedance
Electric Power Supplies
Electrodes
Frequency measurement
Impedance
Impedance measurement
Input impedance
Instrumentation
instrumentation amplifier
Ischemia
Low noise
Myocardial ischemia
Noise reduction
pseudo-sine current
Quadratures
Voltage measurement
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Summary:In this paper, a low power single-path bio-impedance (Bio-Z) measurement system for early detection of acute myocardial ischemia is presented. The fully integrated system consists of a current source, an amplifier, and an analog-to-digital converter (ADC). The system utilizes the in-phase and quadrature (I/Q) components to obtain the real and imaginary parts of the tissue impedance. To achieve this goal, the ADC has been used to separate the I/Q components in addition to digitizing the samples. This can lead to power and silicon area reduction. The proposed circuit exploits the benefits of capacitively-coupled instrumentation amplifier, including inherent DC cancellation, low power, low noise, and high linearity and is implemented in 0.18 µm CMOS technology with a 1 V power supply. This system is designed and tested using a pseudo-sine 2 µA P-P current with a frequency of 1 kHz. The system can measure an input impedance that varies over a range from 0.03-7.5 kΩ with a resolution of 0.766 Ω rms while consuming 2 µW power from the supply. The operation of the system is also shown in the recording of impedance variation with respiration and heartbeat.
ISSN:1932-4545
1940-9990
DOI:10.1109/TBCAS.2022.3213869