Differential mode interferences in biopotential amplifiers

Pallás-Areny, R.; Colominas, J.

doi:10.1109/iembs.1989.96425

Cited by 4 publications

(1 citation statement)

References 3 publications

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“…In highly isolated front ends, they pass the electrodes in a direction toward the earth via the body capacitance. Finally, the total amount of PLI currents flowing via electrodes is multiplied by the electrode impedance imbalance, thus producing the differential PLI voltage drop [6]. This is adversely amplified along with the useful ECG signal and then has to be filtered by analog or digital band-rejection filters.…”

Section: Introductionmentioning

confidence: 99%

Common-Mode Driven Synchronous Filtering of the Powerline Interference in ECG

2022

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Powerline interference (PLI) is a major disturbing factor in ground-free biopotential acquisition systems. PLI produces both common-mode and differential input voltages. The first is suppressed by a high common-mode rejection ratio of bioamplifiers. However, the differential PLI component evoked by the imbalance of electrode impedances is amplified together with the diagnostic differential biosignal. Therefore, PLI filtering is always demanded and commonly managed by analog or digital band-rejection filters. In electrocardiography (ECG), PLI filters are not ideal, inducing QRS and ST distortions as a transient reaction to steep slopes, or PLI remains when its amplitude varies and PLI frequency deviates from the notch. This study aims to minimize the filter errors in wide deviation ranges of PLI amplitudes and frequencies, introducing a novel biopotential readout circuit with a software PLI demodulator–remodulator concept for synchronous processing of both differential-mode and common-mode signals. A closed-loop digital synchronous filtering (SF) algorithm is designed to subtract a PLI estimation from the differential-mode input in real time. The PLI estimation branch connected to the SF output includes four stages: (i) prefilter and QRS limiter; (ii) quadrature demodulator of the output PLI using a common-mode driven reference; (iii) two servo loops for low-pass filtering and the integration of in-phase and quadrature errors; (iv) quadrature remodulator for synthesis of the estimated PLI using the common-mode signal as a carrier frequency. A simulation study of artificially generated PLI sinusoids with frequency deviations (48–52 Hz, slew rate 0.01–0.1 Hz/s) and amplitude deviations (root mean square (r.m.s.) 50–1000 μV, slew rate 10–200 μV/s) is conducted for the optimization of SF servo loop settings with artificial signals from the CTS-ECG calibration database (10 s, 1 lead) as well as for the SF algorithm test with 40 low-noise recordings from the Physionet PTB Diagnostic ECG database (10 s, 12 leads) and CTS-ECG analytical database (10 s, 8 leads). The statistical study for the PLI frequencies (48–52 Hz, slew rate ≤ 0.1 Hz/s) and amplitudes (≤1000 μV r.m.s., slew rate ≤ 40 μV/s) show that maximal SF errors do not exceed 15 μV for any record and any lead, which satisfies the standard requirements for a peak ringing noise of < 25 μV. The signal-to-noise ratio improvement reaches 57–60 dB. SF is shown to be robust against phase shifts between differential- and common-mode PLI. Although validated for ECG signals, the presented SF algorithm is generalizable to different biopotential acquisition settings via surface electrodes (electroencephalogram, electromyogram, electrooculogram, etc.) and can benefit many diagnostic and therapeutic medical devices.

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Section: Introductionmentioning

confidence: 99%

Common-Mode Driven Synchronous Filtering of the Powerline Interference in ECG

2022

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Electrode contact noise in surface biopotential measurements

Fernández

Pallás-Areny

1992

Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society

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Can driven-right-leg circuits increase interference in ECG amplifiers?

Gomez-Clapers¹,

Serrano-Finetti²,

Casanella³

et al. 2011

2011 Annual International Conference of the IEEE Engineering in Medicine and Biology Society

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The Driven-Right-Leg (DRL) circuit has been used for about 50 years to reduce interference due to common-mode voltage in biopotential amplifiers in scenarios that range from fixed equipment supplied from power lines to battery-supplied ambulatory monitors, and for systems that use gelled, dry, textile, and capacitive electrodes. However, power-line interference models predict that for isolation amplifiers, currently mandated by safety standards, power-line interference can often couple mostly in differential mode rather than in common mode. In this work we analyze the effect of the DRL circuit in different ECG leads to elucidate its actual effect on power-line interference reduction. It turns out that that the DRL circuit, which effectively reduces common-mode interference, affects differential-mode interference in an unpredictable way and can increase interference.

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Differential mode interferences in biopotential amplifiers

Cited by 4 publications

References 3 publications

Common-Mode Driven Synchronous Filtering of the Powerline Interference in ECG

Common-Mode Driven Synchronous Filtering of the Powerline Interference in ECG

Electrode contact noise in surface biopotential measurements

Can driven-right-leg circuits increase interference in ECG amplifiers?

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