Digital Filter Optimization for Physiological Measurement Common Mode Interference
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Solution Overview
Problem
Existing physiological measurement devices, such as ECG and EEG devices, face challenges in effectively reducing common mode interference while maintaining the quality of differential signal components, which is crucial for accurate measurements.
Innovation Solution
A method that optimizes digital filter coefficients using samples and definition vectors, allowing for improved common-mode interference mitigation without requiring a reference signal, and incorporates constraints to control filter characteristics, such as DC gain and frequency response, to enhance the quality of differential measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If digital filters are calibrated to reduce common mode interference, then common mode rejection capability is improved, but the quality of differential signal components may deteriorate
Solution Approach 1:
The patent changes the parameters used for filter calibration by optimizing filter coefficients based on multiple criteria simultaneously. Instead of using a single reference channel, the system adjusts coefficients to minimize differences across multiple input channels while preserving differential signal characteristics, thereby achieving both common mode rejection and differential signal quality
Solution Approach 2:
The patent applies partial action by selectively optimizing filter coefficients for specific channels and conditions. Rather than uniformly applying the same filter settings to all channels, the system tailors the filtering approach to individual channel characteristics, reducing adverse effects on differential components while maintaining common mode rejection
2Ease of operation
If a reference input channel is used for calibration, then the calibration process is simplified, but measurement precision may be compromised due to reference signal limitations
Solution Approach 1:
The patent segments the calibration approach by treating each input channel independently rather than relying on a single reference channel. The system determines filter coefficients for each channel based on its own characteristics and minimizes time-domain differences relative to other channels, eliminating reference signal limitations while maintaining calibration simplicity
Solution Approach 2:
The patent creates a universal calibration method that does not depend on any specific reference channel. The same calibration procedure can be applied regardless of which channel might serve as reference, making the process more robust and accurate by utilizing information from all channels equally
3Reliability
If multiple sets of filter coefficients are used for different vector signals, then common mode interference reduction is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by assigning specific filter coefficient sets to specific vector signals or channel combinations. Each set of coefficients is optimized for particular signal characteristics and interference patterns, allowing targeted common mode rejection without requiring complex global optimization across all possible signal types
Data Source
AI summary
The present invention relates to a physiological measurement device (11). In order to reduce common mode interference and/or to improve characteristics of the digital input filters (11) of the measurement device (11) without compromising common mode rejection capabilities of the input filters, it is proposed to calculate by means of optimization a set of filter coefficients for at least one digital input filter (31) associated with a specific input channel of the measurement device (11) based on samples (ci) of multiple input signals (si) of the measurement device (11) corresponding to a test signal (TS) applied to multiple input channels of the measurement device (11) and on at least one definition vector (vj) describing a linear combination of samples (ci) of at least two input channels.