Piezoelectric Acoustic Wave Structure for Lower-Frequency Spurious Waves
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Solution Overview
Problem
Acoustic wave devices using bulk waves in the thickness shear mode generate unnecessary waves at frequencies lower than the resonant frequency, which deteriorate electrical characteristics.
Innovation Solution
The acoustic wave device incorporates a piezoelectric layer made of lithium niobate or lithium tantalate with an interdigital transducer electrode and through holes, where the inclination angle of the notch side surface is other than 0°, effectively dispersing unnecessary waves by positioning through holes between busbars and electrode fingers, thereby reducing or preventing waves near the resonant frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If through holes are provided in the piezoelectric layer to reduce unnecessary waves, then wave dispersion is improved, but the structural integrity and manufacturing precision are compromised
Solution Approach 1:
The piezoelectric layer is segmented by providing through holes at specific positions to divide and disperse the unnecessary waves. The through holes create discontinuities in the wave propagation path, effectively reducing the harmful wave effects while maintaining the overall structural integrity of the device.
Solution Approach 2:
The through holes are strategically positioned in specific regions of the piezoelectric layer where they most effectively disperse unnecessary waves. By concentrating the wave-dispersing function in localized areas rather than uniformly distributing holes throughout, the manufacturing precision requirements are reduced while maintaining effective wave suppression.
2Object-generated harmful factors
If the inclination angle of the notch side surface is increased to enhance wave dispersion, then unnecessary wave reduction is improved, but the manufacturing complexity increases
Solution Approach 1:
The inclination angle of the notch side surface is optimized to a specific range (5 degrees to 45 degrees) to achieve effective wave dispersion. By establishing a quantitative parameter range rather than requiring extreme angles, the solution balances wave dispersion effectiveness with manufacturing feasibility, reducing device complexity while maintaining performance.
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 effectively suppresses unnecessary waves at frequencies lower than the resonant frequency, improving the electrical characteristics of the acoustic wave device by enhancing wave dispersion and reducing spurious signals.
Implementation Method 1
a piezoelectric layer provided on the support, is made of lithium niobate or lithium tantalate
Implementation Method 2
An acoustic reflection portion is located at a position overlapping at least a portion of the IDT electrode in a plan view
Implementation Method 3
The piezoelectric layer includes at least one through hole, and one of the at least one through hole is provided in a portion of the piezoelectric layer between the first busbar and any one of the second electrode fingers
Data Source
AI summary
An acoustic wave device includes a support including a support substrate, a piezoelectric layer on the support, made of lithium niobate or lithium tantalate, and including a first main surface and a second main surface that oppose each other, and an interdigital transducer electrode on the first main surface of the piezoelectric layer. An acoustic reflection portion is at a position overlapping at least a portion of the IDT electrode in a plan view when viewed along a laminating direction of the support and the piezoelectric layer. The IDT electrode includes a first busbar and a second busbar that oppose each other, first electrode fingers each including one end connected to the first busbar, and second electrode fingers each including one end connected to the second busbar and being interdigitated with the plurality of first electrode fingers.