Adjustable Capacitance Circuit for EMI Reduction in Medical Sensors
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Solution Overview
Problem
Existing interventional devices face challenges in reducing electromagnetic interference (EMI) to electrical signals generated by sensors, particularly due to differences in stray capacitance between conductive shields and conductors, which limit the effectiveness of common mode EMI reduction techniques.
Innovation Solution
The implementation of an adjustable capacitance circuit that compensates for differences in stray capacitance between electrical conductors and conductive shields or shafts, allowing for more similar interference coupling and subsequent removal of common mode interference through differential amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrical shielding and grounding techniques are used, then electromagnetic interference protection is provided, but differences in stray capacitance between conductors and shields limit the effectiveness of common mode EMI reduction techniques
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the capacitance value of the adjustable capacitance circuit to match the stray capacitance of each electrical conductor to the conductive shield. This compensation equalizes the capacitance parameters across different conductors, enabling effective common mode EMI reduction through differential amplification while maintaining sensor signal accuracy.
2Reliability
If an adjustable capacitance circuit is added to compensate for stray capacitance differences, then EMI reduction effectiveness is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by designing the adjustable capacitance circuit to serve multiple functions: it compensates for stray capacitance differences, enables common mode EMI reduction, and works with the differential amplifier to enhance sensor signal accuracy. This multi-functionality justifies the added complexity by delivering comprehensive EMI protection across multiple operational aspects.
3Measurement precision
If differential amplification is used for signal processing, then common mode interference can be removed, but the effectiveness is limited by unequal stray capacitance between conductors
Solution Approach 1:
The patent applies preliminary action by pre-compensating the stray capacitance of each electrical conductor to match the conductive shield capacitance using the adjustable capacitance circuit before the differential amplification process. This preliminary capacitance equalization ensures that the subsequent differential amplification can effectively reject common mode interference without being undermined by unequal capacitance values.
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
This approach enhances the sensitivity of sensors by reducing EMI, providing a more reliable technique based on actual detected interference and simplifying processing circuitry by using a differential amplifier for both signal amplification and capacitance control.
Implementation Method 1
One issue faced with such interventional devices is the need to reduce interference to the electrical signals generated by such sensors. Without appropriate measures, electromagnetic interference from nearby electrical devices can confound the analysis of signals from such sensors.
Implementation Method 2
The first electrical conductor and the second electrical conductor each have a stray capacitance to the electrically conductive shield and/or to the electrically conductive shaft. The adjustable capacitance circuit provides an adjustable capacitance between at least one of the electrical conductors and i) the electrically conductive shield that overlaps the electrical conductors and/or ii) the electrically conductive shaft.
Data Source
AI summary
A medical sensing system (100) includes an elongate interventional device (101) and an adjustable capacitance circuit (102). The elongate interventional device (101) includes a sensor (103) having a capacitance (Css). The elongate interventional device (101) also includes a first electrical conductor (104) and a second electrical conductor (105). The first electrical conductor (104) and the second electrical conductor (105) are in electrical contact with the sensor (103) and extend along the elongate interventional device (101). The elongate interventional device (101) also includes i) an electrically conductive shield (106) that overlaps the electrical conductors (104, 105) and/or ii) an electrically conductive shaft (107). The adjustable capacitance circuit (102) provides an adjustable capacitance (CAdj1, CAdj2) between at least one of the electrical conductors (104, 105) and i) the electrically conductive shield (106) that overlaps the electrical conductors (104, 105) and/or ii) the electrically conductive shaft (107).