Optically Controlled MEMS Switch for MRI EMI Immunity
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Solution Overview
Problem
Conventional filtering technologies are inadequate for mitigating electromagnetic interference (EMI) in high-frequency micro electromechanical systems (MEMS) devices, particularly in MRI systems, leading to spurious switching logic transients and potential damage to electrical components.
Innovation Solution
An optically controlled MEMS switch using a current-based opto-isolator to electrically isolate the MEMS device and its driver from control circuitry, converting current control signals into optical signals and then into electrical switching logic to prevent EMI-induced spurious switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional filtering technologies (L-C or R-C networks) are used to mitigate EMI coupling, then spurious switching logic transients are reduced, but the filtering cannot operate at sufficient rates for high-frequency MEMS applications
Solution Approach 1:
The patent replaces the electrical filtering system (L-C or R-C networks) with an optically controlled MEMS switch system. The optical control mechanism uses light to actuate the MEMS switch, creating an electrically isolated control path that is immune to EMI. This substitution enables high-frequency operation (up to 100 MHz or higher) while maintaining switching logic stability, as the optical control path does not suffer from the same bandwidth limitations as conventional electrical filters.
2Measurement precision
If high impedance drive circuits are used in MEMS switches, then switching precision is improved, but the circuits become susceptible to EMI coupling causing spurious transients
Solution Approach 1:
The patent introduces an optical intermediary (light) as a mediator between the control circuitry and the MEMS switch. The optical control signal transfers the switching command without direct electrical connection, creating an isolated control path. This intermediary approach maintains the high impedance drive circuit's precision while eliminating its susceptibility to EMI coupling, as the optical path is immune to electromagnetic interference.
3Reliability
If electrical isolation is implemented using opto-isolators, then EMI-induced spurious switching is prevented, but device complexity increases
Solution Approach 1:
The patent merges the opto-isolator, MEMS switch, and drive circuitry into an integrated device structure. By combining these components into a single packaged unit, the patent reduces the overall system complexity despite the added optical isolation functionality. The integrated design eliminates the need for separate external opto-isolators and simplifies the control circuit architecture, making the EMI-immune switching solution more practical for implementation.
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 effectively prevents EMI-induced spurious switching in MEMS devices, enhancing the reliability of MRI systems by ensuring the receiving coils remain in the desired resonant or non-resonant states during operation, thus reducing the risk of damage and artifacts.
Implementation Method 1
converting current control signals into optical signals
Implementation Method 2
converting the optical signal into electrical switching logic
Implementation Method 3
The MEMS device is operable to vary the electrical assembly between a first conductive state and a second conductive state
Data Source
AI summary
The present embodiments are directed towards the optical control of switching an electrical assembly. For example, in an embodiment, an electrical package is provided. The electrical package generally includes a micro electromechanical systems (MEMS) device configured to interface with an electrical assembly, the MEMS device being operable to vary the electrical assembly between a first electrical state and a second electrical state, a MEMS device driver in communication with the MEMS device and being operable to produce high voltage switching logic from an electrical signal, and an optical detector in communication with the MEMS device driver and configured to produce the electrical signal from an optical signal produced by a light source in response to an applied current-based electrical control signal.