Embedded-Electrode Acoustic Wave Structure for High Q in Smaller Footprints
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Solution Overview
Problem
Existing acoustic wave devices face challenges in achieving size reduction while maintaining high Q-value and capacitance, particularly when reducing the number of electrode fingers in piezoelectric substrates like LiNbO3 or LiTaO3.
Innovation Solution
The acoustic wave device incorporates a piezoelectric layer made of lithium niobate or lithium tantalate with electrodes embedded within the layer, utilizing a bulk wave in a thickness-shear primary mode and an acoustic reflection layer to enhance Q-value and capacitance while reducing size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the number of electrode fingers is decreased to achieve size reduction, then the device size is reduced, but the Q-value decreases
Solution Approach 1:
The patent transitions from planar surface acoustic wave propagation to three-dimensional bulk wave propagation in the thickness direction. By utilizing the thickness dimension of the piezoelectric layer and embedding electrodes within it, the invention achieves size reduction in the planar direction while maintaining high Q-value through volumetric acoustic wave confinement.
Solution Approach 2:
The electrodes are embedded within the piezoelectric layer, with the piezoelectric material surrounding the electrodes. This nested configuration allows the acoustic wave to be confined within the piezoelectric layer volume, improving energy confinement and Q-value while reducing the overall device footprint.
2Volume of moving object
If the number of electrode fingers is decreased to achieve size reduction, then the device size is reduced, but the capacitance decreases
Solution Approach 1:
The invention exploits the thickness dimension of the piezoelectric layer to increase capacitance. By embedding electrodes within the piezoelectric layer and utilizing its full thickness, the effective capacitance area is increased without expanding the planar device footprint, thus achieving size reduction while maintaining or increasing capacitance.
3Volume of moving object
If surface acoustic waves are used with reduced electrode fingers, then device size is reduced, but acoustic wave confinement and loss characteristics deteriorate
Solution Approach 1:
The patent transitions from two-dimensional surface acoustic wave propagation to three-dimensional bulk wave propagation. By utilizing the thickness dimension and confining acoustic waves within the piezoelectric layer volume, the invention achieves superior acoustic wave confinement and reduced energy loss compared to surface acoustic wave devices with reduced electrode fingers.
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 allows for increased Q-value and capacitance while achieving size reduction, with improved acoustic wave confinement and reduced loss.
Implementation Method 1
a bulk wave in a thickness-shear primary mode is utilized. A material of the piezoelectric layer is lithium niobate or lithium tantalate.
Implementation Method 2
The acoustic wave device further includes an acoustic reflection layer. The piezoelectric layer is on the acoustic reflection layer.
Data Source
AI summary
An acoustic wave device includes a piezoelectric layer and first and second electrodes facing each other in a direction intersecting a thickness direction of the piezoelectric layer. The acoustic wave device utilizes a bulk wave in a thickness-shear primary mode. A material of the piezoelectric layer is lithium niobate or lithium tantalate. At least a portion of each of the first and second electrodes is embedded in the piezoelectric layer.