Quartz Plate-Wave Resonator Tuning for Zero Temperature Drift
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Solution Overview
Problem
Current acoustic wave devices face challenges in achieving a tertiary temperature coefficient close to zero, leading to issues with oscillation frequency accuracy and abnormal oscillations, especially in high-frequency applications.
Innovation Solution
The acoustic wave device employs a crystal substrate cut using a right-handed Euler angle (ϕ=0±2°, θ=16.0° to 20.0°, Ψ=0±2°) to select 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, which ensures primary, secondary, and tertiary temperature coefficients are close to zero.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional crystal substrates with standard cutting angles are used, then the device structure is simple and easy to manufacture, but the tertiary temperature coefficient cannot be made close to zero, resulting in oscillation frequency inaccuracy
Solution Approach 1:
The patent applies parameter changes by precisely controlling the Euler angle parameters (φ, θ, Ψ) of the crystal substrate cutting. Specifically, it sets φ=0±2°, θ=16.0° to 20.0°, and Ψ=0±2°, which are optimized parameters that make the primary, secondary, and tertiary temperature coefficients close to zero simultaneously. This resolves the contradiction by changing the cutting parameters to achieve both high frequency accuracy and manageable manufacturing complexity.
2Reliability
If the crystal substrate thickness and electrode film thickness are simply specified, then the manufacturing process is straightforward, but abnormal oscillations occur due to unnecessary vibrations with high electromechanical coupling coefficients
Solution Approach 1:
The patent specifies precise thickness parameters: the crystal substrate thickness is set to make the normalized plate thickness H/λ fall within 1.5 to 2.0, and the electrode film thickness is set to make the normalized excitation electrode film thickness Hs/λ fall within 0.0013 to 0.0085. These parameter changes eliminate unnecessary vibrations with high electromechanical coupling coefficients, ensuring reliable oscillation without excessive manufacturing complexity.
3Object-affected harmful factors
If AT-cut crystal resonators are used for high-frequency applications, then the frequency temperature characteristic is stable, but phase noise and jitter increase, reducing signal quality
Solution Approach 1:
The patent changes the cutting parameters from conventional AT-cut to a specific Euler angle configuration (φ=0±2°, θ=16.0° to 20.0°, Ψ=0±2°) combined with optimized normalized plate thickness (1.5 < H/λ < 2.0). This parameter change simultaneously achieves stable frequency temperature characteristic and reduced phase noise and jitter, resolving the contradiction between temperature stability and signal quality in high-frequency applications.
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 range of temperatures, minimizes phase noise and jitter, and eliminates abnormal oscillations caused by unnecessary vibrations, resulting in improved performance compared to conventional acoustic wave devices and AT-cut resonators.
Implementation Method 1
an acoustic wave device includes a crystal substrate cut by a predetermined Euler angle... and a comb-shape excitation electrode. By the Euler angle, a plate wave is selected that a primary, secondary, and tertiary temperature coefficients of the plate wave are values close to zero
Data Source
AI summary
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 rotational angle specified by the right-handed Euler angle (ϕ, θ, Ψ) is within ranges of ϕ=0±2°, θ=16.0° to 20.0°, and Ψ=0±2°. A plate wave, among the plate waves, having a phase velocity in a range of from 3500-4000 m/s, is selected as a vibration mode of the crystal substrate. When H represents a substrate-thickness of the crystal substrate and λ represents a wavelength of the plate wave, a normalized plate thickness H/λ is in a range of 1.5<H/λ<2.0.