ECG Filter Coefficients for Common Mode Interference Suppression

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Solution Overview

Problem

Physiological measurement devices, such as electrocardiogram (ECG) devices, face challenges in accurately capturing heart signals due to susceptibility to common mode interference from internal and external sources, which can render signal patterns inaccurate for medical diagnostics.

Innovation Solution

The implementation of a method and system that uses digital filters with coefficients calculated through least squares error estimation to minimize time-domain differences between channels, applying finite impulse response filters to each channel to mitigate common mode interference, and a calibration system to determine reference channels and generate filter coefficients for optimal signal processing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If low voltage signals are used to capture polarity changes in organs, then the sensitivity of physiological measurements is improved, but the susceptibility to interference from internal and external sources increases

Engineering Contradiction:

Improvesensitivity of physiological measurementsVSAvoidinterference from internal and external sources

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies common mode rejection by converting the harmful common mode interference into a useful signal cancellation mechanism. By measuring the common mode voltage and using it to generate compensating signals that are subtracted from the differential measurements, the system transforms the interference into a corrective action that improves measurement accuracy.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent introduces an intermediary common mode voltage measurement channel that acts as a mediator between the differential measurement channels and the final output. This intermediate measurement allows the system to separate and remove common mode interference from the differential signals, enabling high-precision measurements despite the presence of interference.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If multiple channels are used to measure electrophysiological signals, then the reliability of measurements is improved, but the complexity of signal processing increases

Engineering Contradiction:

Improvereliability of measurementsVSAvoidcomplexity of signal processing

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the signal processing operations across multiple channels by using a unified common mode rejection approach. Instead of independently processing each channel with complex algorithms, the system combines the channels through common mode voltage measurement and differential amplification, reducing overall processing complexity while maintaining reliability.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent changes the processing parameters by transforming the measurement approach from individual channel analysis to common mode voltage measurement. This parameter change allows the system to achieve reliable measurements through simplified processing operations that focus on removing common mode interference rather than complex multi-channel analysis.

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If digital filters are applied to each channel to minimize time-domain differences, then the common mode interference is reduced, but the computational requirements increase

Engineering Contradiction:

Improvecommon mode interferenceVSAvoidcomputational requirements

Core Design Contradiction:

Object-affected harmful factorsVSUse of energy by moving object

Solution Approach 1:

The patent converts the computational complexity into a benefit by using the common mode voltage measurement to generate filter coefficients that automatically adapt to interference conditions. This approach reduces common mode interference through computationally efficient filtering based on real-time common mode measurements rather than complex multi-channel processing.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS11147517B2Physiological measurement device with common mode interference suppression

Publication Date: 2021.10.19 KONINKLIJKE PHILIPS NV

AI summary

The described embodiments relate to systems, methods, and apparatuses for reducing interference of signals transmitted by a physiological measurement device (108, 210, 312), such as an electrocardiogram device. The physiological measurement device can employ filters (308) that use coefficients to reduce time-domain differences between response signals of the physiological measurement device. The coefficients can be derived during a calibration process where each channel of the physiological measurement device is supplied a test signal (202) for identifying the channel with the slowest or most delayed response. Thereafter, when a monitor signal is compiled from response signals filtered using the coefficients, differences in timing between the response signals will not result in distortion of the monitor signal, thereby rendering the monitor signal more accurate for measurement purposes.