Shielded EMI Filter for Implantable Medical Devices
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Solution Overview
Problem
Existing EMI filters in active implantable medical devices face challenges with parasitic attenuation degradation due to RF cross-coupling and limited high-frequency performance, particularly in military and space applications, where high-frequency emitters are prevalent, and they struggle to handle higher circuit currents required for devices like implantable defibrillators.
Innovation Solution
A shielded three-terminal flat-through EMI/energy dissipating filter with high-frequency shielded electrodes and integrated co-planar inductor elements, which maximizes capacitance and minimizes resistance, allowing for higher current handling and eliminating parasitic RF coupling by surrounding active electrodes with grounded shield plates, optionally incorporating additional passive components for enhanced filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional EMI filters are used in active implantable medical devices, then basic EMI filtering is provided, but parasitic attenuation degradation occurs due to RF cross-coupling and high-frequency performance is limited
Solution Approach 1:
Grounded shield plates are introduced as intermediary elements between the active electrodes to block RF cross-coupling paths. These shield plates act as mediators that prevent direct electromagnetic coupling between adjacent electrodes, thereby eliminating parasitic attenuation degradation while maintaining broadband EMI filtering performance across high frequency ranges.
Solution Approach 2:
The patent converts the harmful effect of RF cross-coupling into a beneficial shielding mechanism. By strategically placing grounded shield plates, the electromagnetic fields that would otherwise cause parasitic attenuation are redirected and contained, transforming the potential harm into an enhanced filtering capability that improves high-frequency performance.
2Power
If existing filter designs are used, then compact size is achieved, but the ability to handle higher circuit currents required for implantable defibrillators is limited
Solution Approach 1:
Multiple functional elements are merged into a single integrated filter structure. The active electrodes, grounded shield plates, and capacitive elements are combined in a compact stacked arrangement that allows the filter to handle high circuit currents while maintaining a small volume suitable for implantable medical devices.
Solution Approach 2:
The filter employs composite construction with conductive electrodes, dielectric materials, and grounded shield plates integrated together. This composite structure enables simultaneous achievement of high current handling capability and compact size by optimizing the electrical and physical properties of each material layer.
3Reliability
If traditional EMI filters are implemented, then basic filtering function is provided, but broadband EMI filtering across high frequencies is not effective
Solution Approach 1:
The filter structure is segmented into multiple discrete functional layers including active electrodes, dielectric separators, and grounded shield plates. This segmentation allows each layer to be optimized for specific frequency ranges, enabling effective broadband EMI filtering while maintaining a relatively simple overall structure that can be manufactured using standard techniques.
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 solution provides effective broadband EMI filtering across a wide frequency range, including high frequencies, and supports higher current circuits, addressing the limitations of prior art filters by eliminating parasitic attenuation and enhancing the filter's performance in harsh electromagnetic environments.
Implementation Method 1
The shield plates are conductively coupled to a common ground and surround the active electrodes to eliminate parasitic RF coupling
Implementation Method 2
the feedthrough capacitor 110 very effectively shunts undesired high frequency EMI signals off of the lead wires to the overall shield housing
Implementation Method 3
A hermetic seal 112 is attached to, typically, a titanium housing 116
Data Source
AI summary
A feedthrough terminal assembly for active implantable medical devices includes an electrically conductive pad for a convenient attachment of wires from either the circuitry inside the implantable medical device or wires external to the device. The electrically conductive pad enables direct thermal or ultrasonic bonding of a circuit board or lead wire to the terminal pin.