Comb-Electrode Acoustic Wave Resonator With Velocity-Tuned Overlap
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Solution Overview
Problem
Acoustic wave resonators with comb-shaped electrodes face issues with lateral-mode spurious due to uniform dielectric coverage, leading to large non-propagating regions and increased electrode size for achieving the same electrostatic capacitance, which affects their frequency characteristics and efficiency.
Innovation Solution
The acoustic wave resonator incorporates a pair of comb-shaped electrodes with distinct regions on the piezoelectric substrate, where the acoustic wave velocity differs between a first region and second regions, allowing for a non-uniform dielectric film distribution that alters the wave propagation, reducing spurious by averaging wave leakage across the electrode fingers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the overlap width of the electrode fingers is increased to reduce lateral-mode spurious, then the frequency characteristics are improved, but the electrode size becomes larger to achieve the same electrostatic capacitance
Solution Approach 1:
The patent applies local quality by creating non-uniform dielectric film thickness across the electrode structure. Specifically, the dielectric film has a first thickness in the overlap region and a second thickness (greater than the first) in the non-overlap region. This localized variation in dielectric properties allows the electrode fingers to be made smaller while maintaining the same electrostatic capacitance, thereby reducing the electrode area without compromising frequency characteristics or lateral-mode spurious performance.
2Reliability
If a film with tilted end face is provided to reduce lateral-mode spurious, then the frequency characteristics are improved, but the device complexity increases
Solution Approach 1:
The patent applies parameter changes by modifying the dielectric film thickness parameter rather than changing the physical geometry of the film edges. Instead of using a tilted end face configuration, the invention varies the dielectric film thickness uniformly across different regions (overlap and non-overlap regions) with different constant thickness values. This parameter-based approach achieves the same effect of reducing lateral-mode spurious while maintaining simpler manufacturing processes and reducing device complexity.
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 reduces spurious by optimizing wave propagation and leakage, maintaining a rectangular overlap region shape while minimizing the size of the acoustic wave resonator, thereby enhancing its frequency characteristics and performance.
Implementation Method 1
an acoustic wave resonator that includes electrode fingers, which excite an acoustic wave, located on a piezoelectric substrate and use a surface acoustic wave propagating through the surface of the piezoelectric substrate
Implementation Method 2
of which a velocity of the acoustic wave is a first velocity... and second regions that are located in the overlap region, in which a velocity of the acoustic wave is a second velocity different from the first velocity
Data Source
AI summary
An acoustic wave resonator includes: comb-shaped electrodes located on a piezoelectric substrate, each including electrode fingers exciting an acoustic wave and a bus bar electrode connecting to the electrode fingers, the comb-shaped electrodes forming an overlap region where the electrode fingers of one of the comb-shaped electrodes overlap the electrode fingers of the other, wherein each of the electrode fingers overlapping in the comb-shaped electrodes includes: a first region that is located in the overlap region, where a velocity of the acoustic wave is a first velocity, and of which a position in a first direction in which the electrode fingers extend changes with respect to a second direction intersecting the first direction; and second regions that are located in the overlap region, where a velocity of the acoustic wave is a second velocity different from the first velocity, and that sandwich the first region in the first direction.