IDT Acoustic Velocity Layout for Transverse Mode Ripple Suppression
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Solution Overview
Problem
Acoustic wave devices employing a piston mode face challenges in suppressing ripples due to lower-order transverse modes, which can occur when the device deviates from an optimum condition, leading to increased ripples and reduced performance.
Innovation Solution
The acoustic wave device incorporates a piezoelectric substrate with an interdigital transducer (IDT) electrode featuring specific acoustic velocity regions and mass addition films, where the first and second low acoustic velocity regions are strategically positioned outside the central region, and high acoustic velocity regions are located outside these low velocity regions, optimizing the acoustic wave propagation to significantly reduce or prevent ripples due to lower-order transverse modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the acoustic wave device uses a conventional IDT electrode design, then the device structure is simple, but ripples due to lower-order transverse modes occur and performance deteriorates
Solution Approach 1:
The patent applies local quality by creating distinct acoustic velocity regions within different areas of the IDT electrode. The central region has a first acoustic velocity, while the edge regions have a second acoustic velocity that is lower than the central region. This spatial variation in acoustic properties suppresses lower-order transverse modes and reduces ripples, improving performance stability without requiring a completely new electrode design
Solution Approach 2:
The patent changes the acoustic velocity parameter across different regions of the IDT electrode by adding mass to the edge regions. This parameter modification creates the desired acoustic velocity distribution (higher in center, lower at edges) that suppresses transverse modes. The mass addition can be achieved through additional electrode fingers or protective films at the edges, altering the local mass density and thus the acoustic velocity
2Adaptability or versatility
If the device operates away from optimum conditions, then operational flexibility is maintained, but ripples increase significantly
Solution Approach 1:
The patent implements preliminary anti-action by pre-configuring the IDT electrode with specific acoustic velocity distributions that counteract the generation of lower-order transverse modes. The edge regions are designed with lower acoustic velocity than the central region, creating a acoustic field distribution that inherently suppresses transverse mode excitation. This preliminary structural arrangement prevents ripple generation even when operating conditions deviate from optima, maintaining performance across a broader operational range
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 reduces or prevents ripples caused by lower-order transverse modes while minimizing the impact on higher-order modes, allowing for improved performance and potential miniaturization of the acoustic wave device.
Implementation Method 1
an acoustic wave device includes a piezoelectric substrate, and an interdigital transducer (IDT) electrode provided on the piezoelectric substrate
Implementation Method 2
The central region includes a low acoustic velocity portion with an acoustic velocity less than an acoustic velocity in another portion of the central region... the first low acoustic velocity region being a region with an acoustic velocity less than the acoustic velocity in the other portion of the central region
Data Source
AI summary
An acoustic wave device includes a piezoelectric substrate, and an IDT electrode provided on the piezoelectric substrate. The IDT electrode includes an overlap region where first and second electrode fingers overlap each other in a first direction. The overlap region includes a central region located in a substantially central portion of the overlap region with respect to a second direction. The central region includes a low acoustic velocity portion with an acoustic velocity less than the acoustic velocity in another portion. The overlap region includes first and second low acoustic velocity regions. The first and second low acoustic velocity regions are respectively located on first-and-second-busbar sides from the central region. The IDT electrode includes first and second high acoustic velocity regions. The first and second high acoustic velocity regions are respectively located outside the first and second low acoustic velocity regions with respect to the second direction.