Harmonic Error Cancellation for Accurate Square-wave-based Bio-Impedance Measurements

Saqib Subhan, Sohmyung Ha

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Bio-impedance spectroscopy, which measures impedance of the tissue over a frequency range, has been widely used to provide crucial information for monitoring human health. Its conventional methods using sine wave current stimulation of the tissue and sine wave demodulation of the resultant voltage provide an accurate impedance measurement, but involve bulky components and power inefficiency due to sinusoidal waveform generation and analog signal multiplication. Instead, the method using square wave clocks can be much more area and power efficient, but inherently has substantial errors in the measured result due to the presence of harmonics in square waves. In this paper we propose a technique to cancel the errors caused by harmonics of the square wave stimulation and demodulation. The technique, based on the fact that the magnitude ratio of all the harmonics of a square wave are known, cancels out harmonic errors by subtracting or adding the square-wave-based measured results at higher harmonics to the fundamental output as a simple post-processing calculation. Simulation results using a generic electrode and tissue model show that this technique can provide a precise measurement of the bio-impedance with <0.5% magnitude error and < 0.2 phase error considering just five frequency multiples. Because this method does not involve sinusoidal signal generation and analog mixing, it is adequate to be integrated in a wearable health monitoring device at low area and power overhead.

Original languageEnglish (US)
Title of host publication40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBC 2018
PublisherInstitute of Electrical and Electronics Engineers Inc.
Pages4273-4276
Number of pages4
ISBN (Electronic)9781538636466
DOIs
StatePublished - Oct 26 2018
Event40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBC 2018 - Honolulu, United States
Duration: Jul 18 2018Jul 21 2018

Publication series

NameProceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS
Volume2018-July
ISSN (Print)1557-170X

Other

Other40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBC 2018
CountryUnited States
CityHonolulu
Period7/18/187/21/18

Keywords

  • Bio-impedance spectroscopy
  • Error cancellation
  • square wave stimulation

ASJC Scopus subject areas

  • Signal Processing
  • Biomedical Engineering
  • Computer Vision and Pattern Recognition
  • Health Informatics

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  • Cite this

    Subhan, S., & Ha, S. (2018). Harmonic Error Cancellation for Accurate Square-wave-based Bio-Impedance Measurements. In 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBC 2018 (pp. 4273-4276). [8513359] (Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS; Vol. 2018-July). Institute of Electrical and Electronics Engineers Inc.. https://doi.org/10.1109/EMBC.2018.8513359