Electrostatic Volume Wave Resonator With Controlled Air Gap Coupling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing bulk acoustic wave resonators face challenges in achieving high electromechanical coupling due to limitations in material strength and symmetry of electrostatic forces, leading to restricted polarization potential and risk of membrane destruction.
Innovation Solution
A bulk acoustic wave resonator design featuring a stack of insulating support, acoustically resonant substrate, and a membrane with a controlled air gap, utilizing a high-level DC differential voltage for direct excitation of oscillating mechanical fields, and a sinusoidal voltage to enhance electrostatic attraction, optimizing the thickness and geometry for constructive interference and increased coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If electrostatic excitation is used to avoid piezoelectric materials, then material versatility is improved, but electromechanical coupling coefficient deteriorates
Solution Approach 1:
The patent changes the physical parameters of the system by introducing a controlled air gap between the membrane and counter-electrode, and by applying high-level DC differential voltage. These parameter changes enable direct excitation of oscillating mechanical fields in non-piezoelectric materials while achieving sufficient electromechanical coupling for practical applications.
2Reliability
If polarization potential is increased to improve coupling, then electromechanical coupling coefficient is improved, but risk of membrane destruction increases
Solution Approach 1:
The patent introduces a controlled air gap as an intermediary element between the membrane and counter-electrode. This air gap acts as a mechanical buffer that allows the application of high DC differential voltages necessary for strong electrostatic coupling, while preventing direct contact and potential breakdown that would occur with smaller gaps or direct contact configurations.
3Reliability
If air gap is reduced to increase coupling, then electromechanical coupling coefficient is improved, but membrane strength limit is exceeded
Solution Approach 1:
The patent optimizes the air gap dimension as a critical parameter, establishing a controlled gap distance that balances two competing requirements: it is small enough to provide strong electrostatic coupling for adequate electromechanical conversion, yet large enough to prevent mechanical contact and exceed the membrane's strength limits under high voltage operation.
4Reliability
If high DC differential voltage is applied for direct excitation, then electromechanical coupling is improved, but air gap breakdown risk increases
Solution Approach 1:
The controlled air gap serves as a dielectric intermediary that enables the application of high DC differential voltages necessary for strong electrostatic excitation. The gap's dimensions and properties are optimized to provide sufficient electrical insulation against breakdown while allowing the high voltage to generate the required electrostatic forces for effective coupling.
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 improved electromechanical coupling, increased deformation tolerance, and higher bias voltage thresholds, reducing the risk of membrane destruction while maintaining high-quality factor resonators suitable for oscillators, filters, and sensors.
Implementation Method 1
The electrostatic force generated in the air gap attracts the resonant substrate towards the counter-electrode, causing stretching of the resonant substrate in its thickness
Implementation Method 2
The resonant substrate is configured by its thickness to obtain a resonance of longitudinal mode acoustic waves generated between its first and second faces when an electrostatic field having a sinusoidal component at the working frequency is generated
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The invention relates to an acoustic volume wave resonator configured so as to resonate at a predetermined work frequency, including: a mounting (12), including a first surface (14) and a second surface (16); a resonating substrate (18), including a first surface (20) and a second surface (22); and a diaphragm (24), rigidly connecting the second surface (16) of the mounting to the first surface (20) of the resonating substrate. The mounting includes an inner cavity (28) and an inner electrode (32) so as to form an air gap area (34) between the inner electrode (24) and a portion (35) of the diaphragm. The resonating substrate is configured so as to generate, between the first surface and second surface thereof, longitudinal-mode sound waves vibrating at the work frequency of the resonator when an electrostatic field having a sine wave component at the work frequency is generated in the air gap area by applying a differential voltage between the diaphragm or the first surface of the resonating substrate and the inner electrode.