Piezoelectric Resonator Holding Arm Tuning for Stable DLD
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Solution Overview
Problem
Conventional resonators experience degraded drive level dependency (DLD) characteristics due to spurious mode coupling with the main mode when the frequency of the spurious mode becomes close to an integer multiple of the main mode frequency, leading to inefficiencies in vibration arm design.
Innovation Solution
A resonator design featuring a base, vibration arms, and a holding arm with specific geometric configurations, including a holding rear arm and a holding side arm, where the frequency ratio of the spurious mode to the main mode is controlled within certain bounds (Fs/Fm < 1.9 or > 2.1) and the length ratio of the holding arm components to the imaginary vibration arm is adjusted (Lc/L5 < 0.520 or > 0.550), to minimize DLD variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the holding arm length is designed with high flexibility to adjust spurious mode frequency, then the design adaptability is improved, but the risk of spurious mode coupling with main mode increases
Solution Approach 1:
The patent applies parameter changes by establishing specific mathematical relationships between the holding arm length (Lh) and vibration arm length (Lv), defining acceptable ranges for the ratio Lh/Lv. This converts the flexible design parameter into a controlled parameter with defined boundaries, ensuring that while design flexibility is maintained, the spurious mode frequency is kept away from integer multiples of the main mode frequency, thus preventing coupling and maintaining reliable DLD characteristics.
2Manufacturing precision
If the holding arm length is increased to adjust spurious mode frequency, then the frequency control is improved, but the device complexity increases
Solution Approach 1:
The patent simplifies the device complexity by establishing a direct proportional relationship between holding arm length and vibration arm length through the ratio parameter Lh/Lv. Instead of independently designing complex holding arm configurations, the invention provides a straightforward design rule where the holding arm length is determined by multiplying the vibration arm length by a factor within the specified range (0.45-0.55), achieving precise frequency control without increasing structural complexity.
3Adaptability or versatility
If the spurious mode frequency is allowed to vary freely, then the design freedom is improved, but the coupling with main mode occurs causing DLD degradation
Solution Approach 1:
The patent applies preliminary anti-action by proactively preventing spurious mode coupling through pre-established design constraints. By defining the acceptable range for the Lh/Lv ratio before the design process begins, the invention ensures that the spurious mode frequency will naturally fall outside the harmful frequency ranges (integer multiples of main mode frequency), thus preventing the harmful coupling effect from occurring in the first place while maintaining design freedom within the defined boundaries.
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 design minimizes the increase in DLD variations and enhances the resonator's performance by maintaining favorable DLD characteristics and allowing for adjustable spurious mode frequencies, thereby improving the overall efficiency and stability of the resonator.
Implementation Method 1
The at least one vibration arm includes a piezoelectric film, an upper electrode, and a lower electrode
Data Source
AI summary
A resonator includes a base, at least one vibration arm, a frame, and a holding arm. The vibration arm includes a piezoelectric film, an upper electrode, and a lower electrode. The inequality Fs/Fm<1.9 or the inequality 2.1<Fs/Fm holds, where Fm is a frequency of a main or primary mode in the vibration arm, and Fs is a frequency of a spurious mode in the holding arm.