Hollow-Disk MEMS Resonators for Stronger Electromechanical Coupling
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Solution Overview
Problem
Existing MEMS resonators face challenges in achieving high electromechanical coupling (Cx/Co) at high frequencies without requiring excessive gap-scaling or high voltage, which is crucial for improving the performance of filters and oscillators in handheld devices.
Innovation Solution
The development of hollow-disk MEMS resonators with asymmetric and symmetric configurations that reduce dynamic mass and stiffness by hollowing out the disk structure, maintaining resonance frequency and transduction area, thereby enhancing electromechanical coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional solid disk resonator structure is used, then structural simplicity is maintained, but electromechanical coupling strength (Cx/Co) is limited
Solution Approach 1:
The solid disk resonator is segmented into a hollow structure with an inner cavity, dividing the originally continuous mass into an outer rim and inner hollow space. This segmentation reduces the dynamic mass participating in vibration while maintaining the outer diameter and electrode overlap area, thereby improving electromechanical coupling strength without excessive gap-scaling.
Solution Approach 2:
Material is extracted from the center of the solid disk to create a hollow cavity, removing excess mass that does not contribute to the electrode-to-resonator overlap area. This extraction reduces the dynamic mass and stiffness of the structure, enhancing the Cx/Co ratio while preserving the essential transduction area at the disk perimeter.
2Reliability
If electrode-to-resonator gap is scaled down to increase Cx/Co, then electromechanical coupling improves, but manufacturing complexity and risk of short-circuit increase
Solution Approach 1:
The resonator structure parameters are changed from solid to hollow configuration, altering the mass and stiffness characteristics. This parameter change enables achieving higher Cx/Co ratios with standard gap dimensions, avoiding the need for excessive gap-scaling and its associated manufacturing precision challenges and short-circuit risks.
3Reliability
If high voltage is applied to increase Cx/Co, then electromechanical coupling improves, but power consumption increases
Solution Approach 1:
The structural parameters of the resonator are changed to a hollow configuration, which improves electromechanical coupling strength through reduced mass and stiffness. This structural modification enables achieving higher Cx/Co with standard operating voltages, thereby reducing power consumption compared to solid disk resonators that would require high voltage to achieve similar coupling levels.
4Reliability
If hollow disk structure is implemented, then electromechanical coupling strength increases, but structural stiffness decreases
Solution Approach 1:
The disk is segmented into a hollow structure where the outer rim maintains structural integrity and stiffness, while the inner cavity reduces overall mass. The outer rim acts as the primary load-bearing structure, preserving sufficient stiffness while enabling higher electromechanical coupling through reduced dynamic mass.
Solution Approach 2:
Different regions of the disk are given different properties: the outer rim maintains full material density for structural strength and electrode overlap, while the inner region is hollowed out to reduce mass. This local differentiation optimizes both stiffness and electromechanical coupling characteristics.
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 hollow-disk design achieves a significant increase in electromechanical coupling strength (up to 7 times that of conventional designs) without scaling the electrode-to-resonator gap, improving filter performance and reducing power consumption in wireless transceivers and oscillators.
Implementation Method 1
hollowing out a disk resonator structure, which reduces the dynamic mass and stiffness of the structure
Implementation Method 2
capacitive-gap transduced resonators have provided some of the highest disk Cx/Co-Q products to date
Data Source
AI summary
System and methods for a hollow-disk radial-contour mode resonator structure. The hollow disk reduces the dynamic mass and stiffness of the structure. Since electromechanical coupling Cx/Co goes as the reciprocal of mass and stiffness, the hollow disk structure has a considerably stronger electromechanical coupling than a solid one at the same frequency, and thus raises Cx/Co without excessive gap-scaling. Several embodiments of hollow disk resonators are detailed, including asymmetric and symmetric disk configurations.