ECG Interference Suppression via Adaptive Signal Cancellation
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Solution Overview
Problem
Existing ECG systems face challenges in accurately interpreting cardiac signals due to power line interference (PLI), which can distort the signals and make interpretation difficult, especially when PLI frequency and amplitude vary, and notch filtering introduces artifacts like ringing.
Innovation Solution
A circuit comprising an interference frequency tracking circuit, a PLI synthesizer circuit, and a summing circuit that digitizes and analyzes the PLI, generates a correction signal matching the PLI's frequency and amplitude, and subtracts it from the ECG signal to suppress PLI effectively across variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If notch filtering is used to remove power line interference, then PLI suppression is achieved, but artifacts like ringing are introduced
Solution Approach 1:
The patent uses the periodic nature of power line interference (a harmful factor) to generate a correction signal that matches the interference characteristics. By synthesizing a signal at the same frequency and phase as the PLI, the system converts the harmful interference pattern into a beneficial cancellation tool, eliminating the need for notch filtering that causes ringing artifacts.
Solution Approach 2:
The system performs preliminary tracking of PLI frequency and synthesis of correction signals before the interference affects the ECG signal quality. The frequency tracking circuit continuously monitors PLI characteristics, and the synthesizer pre-generates correction signals that are then subtracted from the ECG signal, preventing artifact introduction rather than correcting it after the fact.
2Object-affected harmful factors
If traditional filtering methods are used to suppress PLI, then interference reduction is achieved, but signal distortion occurs
Solution Approach 1:
The patent implements a feedback mechanism where the frequency tracking circuit continuously monitors the PLI frequency and adjusts the synthesizer's output accordingly. This closed-loop system ensures that the correction signal remains synchronized with the varying PLI characteristics, maintaining signal accuracy while effectively suppressing interference without the distortion caused by fixed filtering methods.
Solution Approach 2:
The system transitions from static filtering to dynamic adaptation by continuously tracking PLI frequency variations. The frequency tracking circuit and synthesizer adjust in real-time to match changing interference conditions, preserving ECG signal fidelity while maintaining effective PLI suppression across varying power line conditions.
3Measurement precision
If frequency tracking and adaptive synthesis are implemented, then PLI suppression accuracy is improved, but device complexity increases
Solution Approach 1:
The frequency tracking circuit serves itself by using the tracked PLI frequency to automatically control the synthesizer, which in turn generates the correction signal. This self-regulating system eliminates the need for external manual tuning or complex control mechanisms, achieving high frequency tracking accuracy while keeping the overall device complexity manageable through autonomous operation.
Data Source
AI summary
A circuit includes an interference frequency tracking circuit, a PLI synthesizer circuit, and a summing circuit. The interference frequency tracking circuit is configured to track a frequency of an interference signal derived from a target signal, and provide a frequency selection value representing the frequency of the interference signal. The PLI synthesizer circuit is configured to generate, based on the frequency selection value, a correction signal at the frequency of the interference signal, adjust a phase of the correction signal to match a phase of the interference signal in the target signal, and adjust an amplitude of the correction signal to match an amplitude of the interference signal in the target signal. The summing circuit is configured to subtract the correction signal from the target signal.