Quartz Plate-Wave Resonator Cut for Zero-Drift Frequency Stability
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Solution Overview
Problem
Current acoustic wave devices face challenges in achieving a tertiary temperature coefficient close to zero, experiencing abnormal oscillations due to unnecessary vibrations with high electromechanical coupling coefficients, and lacking precision in oscillation frequency accuracy, especially when compared to AT-cut resonators.
Innovation Solution
An acoustic wave device with a crystal substrate cut using a specific right-handed Euler angle (ϕ=0±2°, θ=17.5° to 19.5°, Ψ=0±2°) that selects a plate wave with a phase velocity between 3500 to 4000 m/s and a normalized plate thickness of 1.5<H/λ<2.0, minimizing unnecessary vibrations and optimizing temperature coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional crystal substrates with standard cutting angles are used, then the device structure is simple and manufacturing is easier, but the tertiary temperature coefficient cannot be made close to zero and abnormal oscillations occur
Solution Approach 1:
The patent applies parameter changes by precisely controlling the crystal substrate cutting angles (θ=17° to 23°, φ=0° to 5°, ψ=0° to 5°) to optimize the temperature characteristics. By adjusting these angular parameters, the invention achieves a tertiary temperature coefficient close to zero and eliminates abnormal oscillations, resolving the contradiction between frequency accuracy and manufacturing complexity.
2Speed
If the crystal substrate thickness is reduced to achieve higher frequency operation, then the oscillation frequency increases, but the manufacturing precision requirements increase significantly
Solution Approach 1:
The patent controls the substrate thickness parameter (H) within specific ranges (50μm to 200μm for normalized plate thickness H/λ between 1.5 and 2.0) to achieve high-frequency operation while maintaining manufacturability. This parameter optimization allows higher oscillation frequencies without excessively stringent manufacturing precision requirements.
3Stability of the object's composition
If a plate wave mode with phase velocity of 3500 to 4000 m/s is selected, then the normalized plate thickness can be optimized for stable frequency characteristics, but the selection of appropriate vibration mode becomes more restrictive
Solution Approach 1:
The patent selects plate wave modes with specific phase velocities (3500 to 4000 m/s) and optimizes the normalized plate thickness (H/λ between 1.5 and 2.0) to achieve stable frequency characteristics. This specific parameter selection provides a balance between temperature stability and mode availability, resolving the contradiction between stability and adaptability.
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 configuration enhances oscillation frequency accuracy over a wide temperature range, reduces phase noise and jitter, and eliminates abnormal oscillations by ensuring electromechanical coupling coefficients of unnecessary vibrations are significantly lower than the principal vibration, resulting in improved frequency characteristics.
Implementation Method 1
an acoustic wave device includes a crystal substrate cut by a predetermined Euler angle... at least one comb-shape excitation electrode configured to excite the crystal substrate to make plate waves
Data Source
AI summary
In an acoustic wave device, in a rotated Y-cut crystal substrate to which a rotational angle based on a particular Euler angle is added, a vibration mode located farther in a low phase velocity area than the principal vibration has an electromechanical coupling coefficient K2 lower than that of the principal vibration, and the primary and secondary temperature coefficients of the principal vibration are approximately zero. The acoustic wave device includes a crystal substrate cut from a quartz crystal boule cut by a rotational angle specified by a right-handed Euler angle (ϕ, θ, Ψ), and at least one comb-shape excitation electrode to excite the crystal substrate to make a plate waves. The crystal substrate is made by cutting the quartz crystal boule such that the rotational angle is within ranges of ϕ=0±2°, θ=17.5° to 19.5°, and Ψ=0±2°.