ECG Signal Filtering via Feature Detection and Comb Filter
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Solution Overview
Problem
Existing ECG systems face challenges in accurately isolating heart electrical signals due to interference from power line noise, which can obscure readings and reduce the accuracy of heart activity analysis.
Innovation Solution
A system employing a comb filter to emphasize power line interference, followed by amplitude and phase estimation, and a dual-stage feature detection process using adaptive thresholds to identify and subtract interference, thereby generating a signal substantially free of power line noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If power line interference is removed using traditional filtering methods, then the signal-to-noise ratio is improved, but the accuracy of feature detection deteriorates due to misidentification of ECG features as interference
Solution Approach 1:
The feature detection process is divided into two distinct stages: a first stage that performs initial feature detection to identify potential ECG features, and a second stage that performs additional feature detection to verify and correct the first stage's results. This segmentation allows the system to distinguish between actual ECG features and power line interference more accurately, preventing misidentification while maintaining effective interference removal.
Solution Approach 2:
The system uses the output of the first feature detection stage as input for the second stage, creating a feedback loop where the results are continuously refined. The second stage detects features again and compares them with the first stage results, using this feedback to identify and correct misdetected features before final interference removal, thereby improving overall detection accuracy.
2Difficulty of detecting and measuring
If a comb filter is applied to emphasize interference at selected frequencies, then the interference detection capability is improved, but the complexity of the signal processing system increases
Solution Approach 1:
The comb filter is applied as a preliminary step before feature detection to pre-emphasize power line interference at selected frequencies. This preliminary action enhances the interference signals making them easier to detect and distinguish from actual ECG features in subsequent processing stages, improving detection capability without requiring complex real-time analysis.
Solution Approach 2:
The comb filter acts as an intermediary component that modifies the input signal by emphasizing specific frequency components before they reach the feature detection stages. This intermediary processing simplifies the subsequent detection task by making interference patterns more distinct, thereby improving detection capability while keeping the overall system complexity manageable through modular design.
Data Source
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AI summary
A system and method of filtering input data to remove power line interference is disclosed. The system and method estimates the statistics of the input signal and include determining a value (R) from the ratio of a peak amplitude (Apeak) and a root-mean-square of the amplitudes of the interference harmonics (Arms), calculate a running histogram of the determined value (R) to determine a threshold value (THR), comparing the determined value (R) to the determined threshold value (THR) to make a decision about feature existence, and outputting a feature decision. The system and method include estimating the interference level to determine if interference is low level or high level. The system and method include estimating interference using the feature detection, amplitude and phase; and removing the estimated interference from the signal to result in a signal substantially free of power line interference.