Lithium Niobate Acoustic Wave Electrode Layout for High-Q Scaling
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Solution Overview
Problem
Acoustic wave devices using piezoelectric layers of lithium niobate or lithium tantalate face a challenge in reducing the number of electrode fingers to minimize size while maintaining a high quality factor, as this typically leads to a decrease in quality factor due to wave propagation loss.
Innovation Solution
The acoustic wave device employs bulk waves in a first thickness-shear mode with a piezoelectric layer made of lithium niobate or lithium tantalate, featuring electrodes positioned in a direction intersecting the thickness direction, where the thickness of the piezoelectric layer (d) and the distance between electrode centers (p) are such that d/p is less than or equal to 0.5, allowing for effective excitation of bulk waves without the need for a reflector, thus maintaining a high quality factor even when the size is reduced.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the number of electrode fingers is reduced to minimize device size, then the device dimensions are reduced, but the quality factor decreases due to wave propagation loss
Solution Approach 1:
The patent changes the wave propagation mode from surface waves to bulk waves in thickness-shear mode, and optimizes the d/p ratio parameter to less than or equal to 0.5. This parameter change enables effective excitation of bulk waves with fewer electrode pairs, resolving the contradiction between device size and quality factor
Solution Approach 2:
The patent transitions from two-dimensional surface wave propagation to three-dimensional bulk wave propagation in the thickness direction. This dimensional change allows for more efficient energy confinement and reduced wave propagation loss, enabling high quality factor with reduced electrode count
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 enables good resonant characteristics and a high quality factor by enclosing energy effectively with a small number of electrode pairs, eliminating the need for a reflector and maintaining performance even when the size is minimized.
Implementation Method 1
an acoustic wave device that uses bulk waves in a first thickness-shear mode... a piezoelectric layer made of lithium niobate or lithium tantalate
Data Source
AI summary
An acoustic wave device includes a piezoelectric layer made of lithium niobate or lithium tantalate, and first and second electrodes opposed to each other in a direction that intersects with a thickness direction of the piezoelectric layer. The first and second electrodes are adjacent electrodes, and, when a thickness of the piezoelectric layer is d and a distance between centers of the first and second electrodes is p, d/p is less than or equal to about 0.5.