MEMS Resonator Shield Electrodes for Feed-Through Noise Reduction
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Solution Overview
Problem
Microelectromechanical systems (MEMS) resonators face issues with interfering signals such as induced currents, feed-through currents, and spurious resonance currents, which degrade signal quality, reduce signal-to-noise ratio, and affect frequency stability due to capacitive coupling between drive and sense electrodes and non-active elements.
Innovation Solution
The implementation of resonator electrode shields, made from conductive materials like doped silicon, positioned between non-active elements and drive/sense electrodes to terminate electric field lines, preventing capacitive coupling and reducing interfering signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If drive electrodes are used to generate timing signals in MEMS resonators, then the resonator can produce the desired timing signal, but interfering signals (induced currents, feed-through currents, spurious resonance currents) are generated that degrade signal quality
Solution Approach 1:
A shield electrode is introduced as an intermediary element positioned between the drive electrode and the resonator structure. This shield electrode acts as a mediator that blocks capacitive coupling paths, preventing induced currents and feed-through currents from reaching the resonator and sense electrodes, thereby reducing interfering signals while maintaining the timing signal generation function
2Stability of the object's composition
If non-active elements are included in the MEMS resonator structure for structural support, then the resonator has mechanical stability, but spurious resonance currents are generated that interfere with the timing signal
Solution Approach 1:
The shield electrode serves as a protective intermediary that selectively blocks capacitive coupling to non-active structural elements while allowing the resonator to maintain its mechanical stability. By positioning the shield between the drive electrode and non-active elements, spurious resonance currents are prevented from being generated, while the structural support function remains intact
3Reliability
If capacitive coupling is used between drive and sense electrodes for signal transmission, then the timing signal can be generated and extracted, but interfering signals are coupled along the same paths
Solution Approach 1:
The shield electrode is positioned strategically to block capacitive coupling paths that carry interfering signals while allowing the desired signal transmission path to remain open. The shield acts as a selective barrier that prevents feed-through currents and induced currents from coupling to the sense electrode, while maintaining the capacitive coupling necessary for timing signal extraction
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 effectively mitigates the adverse effects of interfering signals, enhancing the quality and stability of timing signals generated by MEMS resonators by ensuring that only active elements interact with the electrodes, thereby improving signal integrity and frequency stability.
Implementation Method 1
positioned between non-active elements and drive/sense electrodes to terminate electric field lines
Implementation Method 2
preventing capacitive coupling and reducing interfering signals
Implementation Method 3
a charge accumulates on the electrode that applies an electrostatic force between the electrode and an opposite charge built up on the MEMS resonator structure
Implementation Method 4
one or more sense electrodes generate or conduct a time-varying current as a result of capacitive coupling between the moving active elements of the MEMS resonator structure and the sense electrodes
Data Source
AI summary
One embodiment of the present invention sets forth a MEMS resonator system that reduces interference signals arising from undesired capacitive coupling between different system elements. The system includes a MEMS resonator, two or more resonator electrodes, and at least one resonator electrode shield. The resonator electrode shield ensures that the resonator electrodes interact with either one or more shunting nodes or the active elements of the MEMS resonator by preventing or reducing, among other things, capacitive coupling between the resonator electrodes and the support and auxiliary elements of the MEMS resonator structure. By reducing the deleterious effects of interfering signals using one or more resonator electrode shields, a simpler, lower interference, and more efficient system relative to prior art approaches is presented.