Current-Mode Biopotential Circuit for EMI-Resistant Measurement
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Solution Overview
Problem
Existing biopotential measurement systems are susceptible to electromagnetic interference (EMI), which degrades signal quality and complicates measurements, particularly in clinical environments where low-level signals are prone to interference from devices like electrosurgical instruments and microwave ablation units.
Innovation Solution
A biopotential measurement system that measures current rather than voltage, using high resistance resistors and amplifiers to isolate the measurement subject from external interference, allowing for robust, portable, and low-power devices with improved signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage measurement is used in conventional biopotential systems, then the system can detect biopotential signals, but the system becomes highly susceptible to electromagnetic interference (EMI) and requires large footprint with high power consumption
Solution Approach 1:
The patent replaces conventional voltage measurement electronics with a current detection system using a current detector and high resistance resistors. This substitution fundamentally changes the measurement approach from voltage-based to current-based, which inherently rejects common-mode EMI signals while maintaining biopotential detection capability, thereby resolving the contradiction between measurement precision and EMI susceptibility
Solution Approach 2:
The patent changes the measurement parameter from voltage to current. By measuring current through high resistance resistors connected to electrodes instead of measuring voltage directly, the system achieves immunity to common-mode EMI while maintaining the ability to detect biopotential signals, thus improving signal-to-noise ratio without sacrificing measurement capability
2Measurement precision
If conventional voltage measurement systems are used, then biopotential signals can be measured, but the devices require large footprint and high power consumption
Solution Approach 1:
The patent replaces complex voltage measurement circuitry with a simplified current detection system. The current detector combined with high resistance resistors eliminates the need for bulky operational amplifiers and complex filtering circuits required in conventional voltage-based systems, enabling portable devices with small footprint while maintaining biopotential measurement precision
Solution Approach 2:
The high resistance resistors in the current detection circuit automatically provide both current measurement and EMI rejection functions without requiring additional active components. The system uses the inherent properties of the resistors and current detector to achieve measurement precision, eliminating the need for large footprint voltage measurement electronics
3Adaptability or versatility
If conventional ECG lead systems with multiple electrodes are used, then comprehensive biopotential information can be obtained, but the system complexity and susceptibility to EMI increase
Solution Approach 1:
The patent creates a universal current detection circuit that can measure biopotential signals from multiple electrode configurations (three-lead, five-lead, twelve-lead) using the same fundamental circuit topology. The current detector and high resistance resistors provide a unified measurement approach that works across different lead systems, reducing overall system complexity while maintaining measurement versatility
Solution Approach 2:
By changing the measurement parameter to current, the patent simplifies the circuit requirements for handling multiple electrodes. The current detection method inherently provides EMI rejection for all leads simultaneously, eliminating the need for complex per-lead filtering and processing circuits, thus reducing system complexity while maintaining adaptability to various ECG configurations
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively mitigates EMI, enabling reliable biopotential measurements with enhanced signal quality, reduced power consumption, and the ability to measure electrode impedance, while maintaining a small footprint suitable for diverse medical applications.
Implementation Method 1
a first biopotential measurement device which isolates the measured object from the measuring apparatus and interference to provide a true differential biopotential measurement
Implementation Method 2
A biopotential measurement system that measures current rather than voltage, using high resistance resistors and amplifiers
Data Source
AI summary
System and apparatus for measuring biopotential and implementation thereof. A device for mitigating electromagnetic interference (EMI) thereby increasing signal-to-noise ratio is disclosed. Specifically, the present disclosure relates to an elegant, novel circuit for measuring a plurality of biopotentials in useful in a variety of medical applications. This allows for robust, portable, low-power, higher S/N devices which have historically required a much bigger footprint.