ECG Multiplexer Reference Switching for Noise Reduction
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Solution Overview
Problem
Existing ECG systems face issues with switching noise introduced by multiplexing multiple analog signals, which can distort bioelectric signal outputs, and existing solutions have limitations in effectively mitigating these artifacts.
Innovation Solution
Incorporating a double pole double throw (DPDT) switch into the multiplexer that first connects to a reference signal and then to the incoming ECG signal, along with control circuitry and a differential amplifier to manage the switching and reduce noise, and using an analog-to-digital converter connected to a processor for signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If multiple analog ECG signals are multiplexed to a single digital-analog converter, then the number of converters is reduced and system complexity is lowered, but switching noise is introduced into the signal output
Solution Approach 1:
A reference signal is introduced as an intermediary between the multiplexer switching action and the differential amplifier. The DPDT switch alternately connects the differential amplifier to either the ECG signal or the reference signal, allowing the amplifier to reject common-mode switching noise while preserving the differential ECG signal.
Solution Approach 2:
The differential amplifier configuration with common-mode feedback maintains equal potential levels for both inputs during switching transitions. By keeping the non-inverting and inverting inputs at the same potential during the reference signal phase, switching noise is minimized and rejected as common-mode signal.
2Device complexity
If a multiplexer is used to transfer multiple ECG signals through a single converter, then hardware resources are reduced, but signal accuracy and clarity deteriorate due to switching noise
Solution Approach 1:
Common-mode feedback is implemented in the differential amplifier to continuously monitor and correct the common-mode voltage level. This feedback mechanism actively compensates for switching noise and maintains signal accuracy despite the presence of multiplexer switching artifacts.
Solution Approach 2:
The system dynamically changes the connection state of the DPDT switch between signal mode and reference mode, altering the operational parameters of the differential amplifier. This periodic parameter change allows the amplifier to adapt to switching noise conditions and maintain measurement precision.
3Object-generated harmful factors
If existing common-mode feedback approaches are used at every stage of amplification, then switching noise is partially mitigated, but device complexity and circuit stages increase
Solution Approach 1:
The harmful switching noise component is extracted and separated from the useful ECG signal by using the reference signal approach. The DPDT switch isolates the switching noise into the reference signal path, allowing it to be rejected by the differential amplifier while preserving the clean ECG signal path.
Data Source
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AI summary
Medical catheterization is carried out by receiving a plurality of analog bioelectric signals in respective channels and multiplexing the bioelectric signals in respective selection events. The selection events comprise making a first connection with a reference voltage, thereafter breaking the first connection and making a second connection with one of the bioelectric signals. The method is further carried out by outputting the multiplexed bioelectric signals to an analog-to-digital converter.