ECG Signal Acquisition with Polarity-Adjusted Reference for Motion Artifact Reduction
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Solution Overview
Problem
Ambulatory ECG monitoring is hindered by motion artifacts, which existing digital adaptive filtering techniques struggle to effectively reduce, particularly in low-power and ambulatory applications.
Innovation Solution
An ECG signal acquisition system that includes an analogue readout unit, an ADC unit, a reference signal processing unit to generate a new reference signal based on the correlation and polarity between the ECG signal and electrode-tissue impedance signal, and a digital filter unit to calculate a digital motion artifact estimate, utilizing a digital adaptive filter like the LMS filter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If digital adaptive filtering is used to reduce motion artifacts, then motion artifact reduction is improved, but the system complexity and power consumption increase
Solution Approach 1:
The patent applies preliminary action by pre-calculating the polarity of the electrode-tissue impedance signal and generating a polarity-adjusted reference signal before the adaptive filtering process. This preliminary preparation ensures that the reference signal has the correct polarity alignment with the ECG signal, improving the effectiveness of motion artifact reduction while maintaining reasonable system complexity
Solution Approach 2:
The patent changes the polarity parameter of the reference signal based on the detected polarity of the electrode-tissue impedance signal. By dynamically adjusting the polarity parameter (multiplying by +1 or -1), the system optimizes the correlation between the reference signal and motion artifacts, thereby improving artifact reduction effectiveness without requiring complex additional hardware
2Reliability
If digital adaptive filtering is used to reduce motion artifacts, then motion artifact reduction is improved, but power consumption increases
Solution Approach 1:
The system performs preliminary polarity detection and reference signal adjustment before the main adaptive filtering computation. By preparing the correctly polarized reference signal in advance, the system avoids iterative polarity adjustments during runtime, reducing the overall computational load and power consumption while maintaining effective motion artifact reduction
Solution Approach 2:
The patent extracts the polarity information from the electrode-tissue impedance signal and separates it as a distinct parameter. This extraction allows the system to handle polarity adjustment as a simple preprocessing step rather than integrating it into the complex adaptive filtering algorithm, thereby reducing computational complexity and power consumption
3Measurement precision
If the electrode-tissue impedance signal has opposite polarity to the ECG signal, then motion artifact correlation is reduced, but filtering effectiveness deteriorates
Solution Approach 1:
The patent applies inversion by detecting the polarity of the electrode-tissue impedance signal and inverting it (multiplying by -1) when the polarity is opposite to that of the ECG signal. This inversion ensures that the reference signal always has the correct polarity alignment to correlate with the motion artifacts in the ECG signal, maintaining filtering effectiveness regardless of the original impedance signal polarity
Solution Approach 2:
The system dynamically changes the polarity parameter of the reference signal based on the detected polarity of the electrode-tissue impedance signal. By adjusting this parameter (setting to +1 or -1), the system ensures optimal correlation between the reference signal and motion artifacts, thereby maintaining high filtering effectiveness under varying polarity conditions
Data Source
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AI summary
The invention relates to a biopotential signal acquisition system (100) comprising: an analogue readout unit (10) configured to receive an analogue biopotential signal (BS1), which may be acquired from at least one electrode attached to a body; and to extract an analogue measured biopotential signal (BS2) and an analogue reference signal (REF1); an ADC unit (20) configured to provide a digital version of the analogue measured biopotential signal (BS2) and the analogue reference signal (REF1); a digital filter unit (40) configured to calculate a digital motion artifact estimate (MA) based on the digital version of the measured biopotential signal (BS2) and the reference signal (REF1). The system further comprises a reference signal processing unit (30) configured to convert the reference signal (REF1) into a new reference signal (REF2) being provided to the digital filter unit (40) based on the correlation between the measured biopotential signal (BS2) and the reference signal (REF1). The invention also relates to an electronic device and a method for acquisition of biopotential signals.