Acoustic Wave Electrode Layout for Compact Piston Mode Control
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Solution Overview
Problem
The increase in size of acoustic wave devices due to the need to establish a piston mode by increasing the width of the edge region to differentiate sound velocities in the central and edge regions.
Innovation Solution
The acoustic wave device is designed with a specific weight distribution and sound velocity profile by adjusting the width and weight per unit length of electrode fingers in the central, intermediate, and edge regions, using additional films to control sound velocities without enlarging the device size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the width of the edge region is increased to differentiate sound velocities in the central and edge regions, then the piston mode is established and spurious is suppressed, but the device size increases
Solution Approach 1:
The patent applies local quality by creating distinct weight per unit length zones (central region with first weight, intermediate region with second weight, edge region with third weight) within the electrode finger structure. This allows different regions to have optimized acoustic properties - the central region maintains standard sound velocity for primary signal transmission, while the edge region with reduced weight creates higher sound velocity to suppress spurious modes, achieving piston mode without increasing overall device dimensions.
Solution Approach 2:
The patent changes the physical parameter of weight per unit length of the electrode fingers by adjusting metal layer thickness or material composition across different regions. Specifically, the edge region electrode fingers have reduced weight per unit length compared to the central region, which modifies the local sound velocity and enables spurious suppression while maintaining compact device size.
2Reliability
If the weight per unit length of electrode fingers is reduced in the edge region to increase sound velocity, then spurious is suppressed, but the electrode finger strength may be compromised
Solution Approach 1:
The patent employs composite material structures in the electrode fingers, combining multiple metal layers with different properties. The electrode finger structure includes a base metal layer providing mechanical strength and an additional metal layer with optimized weight characteristics. This composite approach allows the edge region to have reduced overall weight per unit length for spurious suppression while the base layer maintains sufficient structural strength.
Solution Approach 2:
The patent addresses the strength concern by transitioning from a one-dimensional weight reduction approach to a multi-dimensional solution. Instead of simply thinning the entire electrode finger, the design uses varied metal layer configurations (different thicknesses, materials, and arrangements) across central, intermediate, and edge regions. This dimensional complexity allows localized weight optimization without compromising overall structural integrity.
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
The design achieves the piston mode while maintaining a compact device size by optimizing sound velocity differences through controlled width and weight adjustments, reducing the length of the edge region and maintaining effective acoustic wave confinement.
Implementation Method 1
a piezoelectric layer; and a pair of interdigital electrodes provided on the piezoelectric layer
Implementation Method 2
a first sound velocity of an acoustic wave propagating in the intermediate region is slower than a second sound velocity of the acoustic wave propagating in the central region and a third sound velocity of the acoustic wave propagating in the edge region is faster than the second sound velocity
Data Source
AI summary
An acoustic wave device includes a piezoelectric layer, and a pair of interdigital electrodes provided on the piezoelectric layer. Each of the pair of interdigital electrodes has electrode fingers and a bus bar to which the electrode fingers are connected. An intersection region where the electrode fingers intersect each other includes an edge region, a central region, and an intermediate region located between the edge region and the central region. When a weight per unit length in the longitudinal direction of a single-layer or multilayer film including a metal layer of at least one of the electrode fingers provided on the piezoelectric layer is a first weight in the central region, a second weight in the intermediate region, and a third weight in the edge region, the second weight is larger than the first weight and the third weight is smaller than the first weight.