MEMS Gyroscope Resonance Frequency Matching via Electrostatic Stiffness Tuning
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Solution Overview
Problem
Existing MEMS gyroscope technologies face challenges in matching the resonance frequency between the drive mode and sense mode without using additional electrodes, which increases costs and affects area density.
Innovation Solution
Applying a direct current (DC) voltage through high impedance circuitry to the sense electrodes, utilizing the same electrodes for both sensing and frequency matching, and incorporating a frequency matching circuitry that includes diodes, capacitors, and switches to adjust the stiffness of the proof mass, thereby matching the resonance frequency without dedicated electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dedicated electrodes are added to match resonance frequency, then resonance frequency matching is improved, but area density and device complexity deteriorate
Solution Approach 1:
The sense electrodes are made to serve dual functions: sensing the proof mass movement and matching the resonance frequency between drive and sense modes. By applying DC voltage through high impedance circuitry to the sense electrodes, the system achieves frequency matching without requiring dedicated electrodes, thus maintaining area density while improving reliability
Solution Approach 2:
The patent combines the sensing function and frequency matching function into a single electrode structure. The sense electrodes are electrically connected to both the sensing circuitry and the frequency matching circuitry, allowing one component to fulfill multiple roles and eliminating the need for separate dedicated electrodes
2Reliability
If dedicated electrodes are added to match resonance frequency, then resonance frequency matching is improved, but device complexity increases
Solution Approach 1:
The sense electrodes perform both sensing and frequency matching functions, eliminating the need for separate dedicated electrodes and their associated supporting circuitry. This reduces device complexity while maintaining the reliability of resonance frequency matching
Solution Approach 2:
The patent merges the frequency matching circuitry with the existing sensing circuitry, allowing both functions to share common components and reducing overall device complexity
3Reliability
If DC voltage is applied through low impedance circuitry, then frequency matching is effective, but received signal quality deteriorates
Solution Approach 1:
High impedance circuitry is introduced as an intermediary between the DC voltage source and the sense electrodes. This intermediary allows DC voltage to be applied for frequency matching while blocking the passage of significant current that would interfere with the AC sensing signals, thus maintaining both frequency matching effectiveness and signal quality
Solution Approach 2:
The patent changes the impedance parameter of the circuitry connecting to the sense electrodes. By using high impedance circuitry instead of low impedance circuitry, the system can apply DC voltage for frequency matching without significantly loading the sensing circuit and degrading signal quality
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 improves performance by matching the resonance frequency between the drive and sense modes with minimal impact on received signals and area density, eliminating the need for additional electrodes and reducing silicon area usage.
Implementation Method 1
The frequency matching circuitry is configured to apply a DC voltage to the sense electrodes. The DC voltage is configured to change a stiffness of a spring of the proof mass.
Data Source
AI summary
In some embodiments, a micro electro mechanical system (MEMS) includes a proof mass, sense electrodes, sense circuitry, and a frequency matching circuitry. The proof mass is configured to move responsive to stimuli. The sense electrodes are configured to generate a signal responsive to the proof mass moving. The sense circuitry is coupled to the sense electrodes. The sense circuitry is configured to receive the generated signal and further configured to process the generated signal. The frequency matching circuitry is configured to apply a DC voltage to the sense electrodes. The DC voltage is configured to change a stiffness of a spring of the proof mass. According to some embodiments, the change in the stiffness of the spring matches a resonance frequency between a sense mode and a drive mode. According to some embodiments, the sense electrodes are a comb structure.