Acoustic wave device
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Solution Overview
Problem
Existing acoustic wave devices face challenges in miniaturization as reducing the number of electrode fingers leads to a decrease in the Q factor and deterioration of resonance characteristics, with interference between electrode fingers and busbars causing spurious waves.
Innovation Solution
The use of a piezoelectric film made of lithium niobate or lithium tantalate with a specific configuration of electrode fingers and busbars, where the electrode fingers are coupled to opposite busbars and the gaps between them are optimized to facilitate bulk waves in a thickness-shear mode, allowing for miniaturization without compromising the Q factor or resonance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the number of electrode fingers is reduced to miniaturize the device, then the device size is reduced, but the Q factor decreases
Solution Approach 1:
The patent changes the gap length parameter from a conventional small value to a specific optimized value (about 0.92p or longer), which fundamentally alters the acoustic wave propagation characteristics and enables miniaturization without Q factor degradation
2Volume of moving object
If the distance between electrode fingers and busbars is made short to reduce device size, then the device is miniaturized, but spurious waves are generated due to interference
Solution Approach 1:
The patent optimizes the gap length parameter to about 0.92p or longer, which changes the electromagnetic and acoustic field distribution to eliminate interference between busbars and electrode fingers, preventing spurious wave generation while maintaining compact dimensions
Solution Approach 2:
The optimized gap acts as an intermediary space that mediates the interaction between busbars and electrode fingers, preventing direct interference while allowing compact integration of components
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 the miniaturization of acoustic wave devices with an increased Q factor and reduced deterioration of resonance characteristics, maintaining impedance and attenuation performance.
Implementation Method 1
a piezoelectric film made of lithium niobate or lithium tantalate... configured to use bulk waves in a first thickness-shear mode
Data Source
AI summary
An acoustic wave device includes a piezoelectric film made of lithium niobate or lithium tantalate, first and second busbar electrodes located on the piezoelectric film and opposite to each other, and first and second electrode fingers and each including one end coupled to the first busbar electrode or the second busbar electrode. The acoustic wave device uses bulk waves in a first thickness-shear mode. A first gap is provided between the first busbar electrode and the second electrode finger. A second gap is provided between the second busbar electrode and the first electrode finger. A length of the first gap and the second gap in a direction in which the first and second electrode fingers extend is about 0.92p or longer, where p is a center-to-center distance between the adjacent first and second electrode fingers.