Corner-Coupled MEMS Resonator Array for Low Motional Impedance
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Solution Overview
Problem
Conventional MEMS resonator designs face high motional impedance issues at high frequencies, which are exacerbated by out-of-plane bending modes and electrostatic actuation, leading to unsatisfactory electrical characteristics and spurious resonances.
Innovation Solution
A MEMS resonator array design featuring piezoelectric resonators coupled at their corners, with overlapping regions between adjacent resonators to minimize motional impedance, allowing for mechanical and electrical coupling while maintaining a compact structure and reducing unnecessary space, thus avoiding the need for connecting beams that increase size and introduce additional vibration modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the resonator size is reduced to increase resonant frequency, then the resonant frequency increases, but the electrical impedance becomes unacceptably high
Solution Approach 1:
Multiple resonators are merged into a single array structure where they are mechanically coupled through corner-to-corner connections. This combining approach allows the array to achieve the resonant frequency characteristics of small resonators while the collective structure provides lower electrical impedance compared to individual small resonators.
2Ease of operation
If electrostatic actuation is used to actuate resonators, then the resonators can be actuated, but the motional impedance becomes unacceptably high
Solution Approach 1:
The patent replaces electrostatic actuation with piezoelectric actuation. Piezoelectric materials convert electrical signals directly to mechanical deformation, providing effective actuation with significantly lower motional impedance compared to electrostatic methods. This substitution eliminates the high impedance issue while maintaining the ability to actuate the resonators.
3Device complexity
If connecting beams are used to couple resonators, then the resonators are connected, but the device size increases and spurious resonances are introduced
Solution Approach 1:
The resonators are directly coupled corner-to-corner without intermediate connecting beams. This merging approach eliminates the need for separate coupling structures, thereby reducing the overall device size and avoiding the introduction of spurious resonances that would arise from additional beam structures.
Solution Approach 2:
The connecting beams are extracted or removed from the design. By eliminating these intermediate coupling elements, the patent achieves resonator coupling through direct corner connections, which reduces device complexity and avoids the volume increase and spurious resonance issues associated with beam-based coupling.
4Adaptability or versatility
If out-of-plane bending modes are allowed, then the resonator structure is flexible, but the quality factor becomes low at high frequencies
Solution Approach 1:
The patent enforces in-plane vibration modes by designing the resonator structure and coupling mechanism to constrain out-of-plane bending. By controlling the local vibration characteristics through corner-to-corner coupling and piezoelectric actuation oriented for in-plane motion, the quality factor is maintained at high frequencies while the structure remains adaptable for various device configurations.
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 design achieves reduced motional impedance and improved electrical characteristics by ensuring effective mechanical and electrical coupling between resonators, maintaining a high quality factor and resonant mode shape, even at high frequencies.
Implementation Method 1
adding a piezoelectric material, such as a layer of thin film of aluminum nitride (AlN), on top of the resonator yields a resonator with lower motional impedance
Implementation Method 2
MEMS resonators are small electromechanical structures that vibrate at high frequencies and are often used for timing references, signal filtering
Data Source
AI summary
A MEMS resonator array is provided with improved electrical characteristics and reduced motional impedance at high frequency applications. The MEMS resonator array includes a pair of first piezoelectric resonators that are opposed to each other with a space defined therebetween. Moreover, the MEMS resonator array includes a pair of second piezoelectric resonators that are opposed to each other and that are each coupled to respective corners of each of the first piezoelectric resonators. As such, each of the second piezoelectric resonators is partially disposed in the space defined between the pair of first piezoelectric resonators.