Acoustic Wave Electrode Structure for Wider Piston Mode Range
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Solution Overview
Problem
Existing acoustic wave devices have difficulty in sufficiently widening the frequency range for establishing the piston mode, resulting in a narrow frequency range where spurious due to the transverse mode can be suppressed.
Innovation Solution
The acoustic wave device incorporates a piezoelectric substrate with a support substrate and a piezoelectric layer, featuring paired busbars and electrode fingers, through-holes in the piezoelectric layer, and a hollow portion in the support substrate, along with a protruding portion of the piezoelectric layer that constrains the substrate, allowing for effective suppression of the transverse mode across any frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional IDT electrode configuration is used, then the device structure is simple, but the frequency range for establishing piston mode is narrow
Solution Approach 1:
The piezoelectric layer is segmented by creating through-holes at specific positions, dividing it into multiple regions with different acoustic velocities. This segmentation allows the central region to maintain piston mode while edge regions suppress transverse modes, thereby widening the frequency range for piston mode establishment without significantly complicating the overall device structure
Solution Approach 2:
Different regions of the piezoelectric layer are given different acoustic velocity characteristics through the through-hole configuration. The central region maintains high acoustic velocity for piston mode operation, while edge regions with through-holes have reduced acoustic velocity to suppress transverse modes. This local differentiation enables wide frequency range piston mode operation while maintaining structural simplicity
2Adaptability or versatility
If the piston mode is established using conventional methods, then transverse mode suppression is achieved, but only in a narrow frequency range
Solution Approach 1:
The piezoelectric layer is divided into central and edge regions through strategic placement of through-holes. This segmentation enables the central region to support piston mode across a wide frequency range while edge regions with through-holes suppress transverse modes, achieving broad frequency range transverse mode suppression without complex device modifications
Solution Approach 2:
Through-holes are introduced into the piezoelectric layer at edge regions, creating a porous structure that reduces acoustic velocity in these areas. This porous configuration effectively suppresses transverse modes across a wide frequency range while maintaining the overall structural integrity and simplicity of the piezoelectric substrate
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 suppression of the transverse mode in any frequency range, enhancing the operational efficiency of the acoustic wave device by maintaining a piston mode state over a wider frequency range.
Implementation Method 1
an IDT electrode on the piezoelectric layer and including paired busbars and a plurality of electrode fingers
Implementation Method 2
Acoustic wave filter devices have been widely used for filters for mobile phones and the like
Data Source
AI summary
An acoustic wave device includes a piezoelectric substrate including a support substrate and a piezoelectric layer, and an IDT electrode. In the IDT electrode, a second gap region includes gap portions on an extension line in an electrode finger extending direction. A through-hole is provided in a portion of the piezoelectric layer overlapping a gap portion in plan view. A recessed portion is provided in a portion of the support substrate overlapping the through-hole in plan view. The recessed portion extends farther toward a center of the IDT electrode in the electrode finger extending direction than the portion including the through-hole. One or more layers in the piezoelectric substrate are constraining layers that constrain the piezoelectric layer at a portion overlapping an intersection region in plan view, and the piezoelectric layer includes a protruding portion that protrudes farther in the electrode finger extending direction than at least one constraining layer.