IDT Electrode Mass Layout for Elastic Wave Confinement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Elastic wave devices utilizing a piston mode face challenges in confining energy, leading to unwanted wave generation between resonant and anti-resonant frequencies, as energy of unwanted waves is readily confined near the surface of the piezoelectric body.
Innovation Solution
The elastic wave device incorporates a piezoelectric body with an IDT electrode featuring a center region and low-acoustic-velocity regions on both sides, along with high-acoustic-velocity regions, and adjustable electrode finger duties and masses to effectively confine elastic waves and reduce unwanted waves, particularly by using additional mass films and dummy electrode fingers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the IDT electrode uses a conventional piston mode configuration with increased electrode width in edge regions, then the acoustic velocity in edge regions is lowered to confine elastic wave energy, but unwanted waves are readily confined close to the surface of the piezoelectric body generating large unwanted waves between resonant and anti-resonant frequencies
Solution Approach 1:
The IDT electrode is divided into multiple regions along the elastic wave propagation direction: a center region with standard electrode characteristics, and first and second end regions with modified electrode characteristics (reduced mass). This segmentation allows different regions to serve different functions - the center region confines elastic wave energy while the end regions prevent unwanted wave generation by reducing mass where surface confinement occurs
Solution Approach 2:
The electrode structure is designed with non-uniform mass distribution along the propagation direction. The end regions have reduced mass compared to the center region, creating local variations in acoustic velocity and mass properties. This local quality adjustment allows the electrode to simultaneously achieve energy confinement in the center and unwanted wave suppression at the ends
2Loss of energy
If additional mass films are added to the IDT electrode to adjust acoustic velocity, then elastic wave confinement is improved, but the device complexity and manufacturing process become more complex
Solution Approach 1:
The invention adjusts the mass parameter of the IDT electrode by varying the electrode finger dimensions (width, length, or both) in different regions. Instead of adding separate mass films, the mass is directly controlled through geometric parameter changes of the electrode fingers themselves, achieving the desired acoustic velocity profile while maintaining a relatively simple single-layer electrode structure
3Loss of energy
If the electrode finger duty is increased in edge regions to lower acoustic velocity, then elastic wave energy is confined, but unwanted waves between resonant and anti-resonant frequencies are enhanced
Solution Approach 1:
The electrode is segmented into center and end regions with different duty ratios. The center region maintains a higher duty ratio for energy confinement, while the end regions use a lower duty ratio to prevent unwanted wave generation, thus maintaining reliable frequency response characteristics across the operating band
Solution Approach 2:
Different duty ratios are applied locally to different regions of the electrode. The center region has one duty ratio optimized for energy confinement, while the end regions have a different duty ratio optimized for suppressing unwanted waves, creating local quality variations that simultaneously achieve both goals
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 significantly reduces unwanted waves, improving return loss and preventing Rayleigh wave leakage, thereby enhancing the confinement of the elastic wave within the desired frequency band.
Implementation Method 1
an elastic wave device that utilizes a piston mode... an IDT electrode provided on the piezoelectric body
Implementation Method 2
the acoustic velocity in the first and second edge regions is lower than the acoustic velocity in the center region... the energy of elastic waves is confined
Implementation Method 3
a first high-acoustic-velocity region between the first busbar and the first low-acoustic-velocity region and in which an acoustic velocity is higher than in the center region
Data Source
AI summary
An elastic wave device includes an IDT electrode provided on a piezoelectric substrate and including a first end region including one end of the IDT electrode in an elastic wave propagation direction, a second end region including the other end of the IDT electrode in the elastic wave propagation direction, and an inner region that is located farther toward an inside than the first and second end regions in the elastic wave propagation direction, includes first and second high-acoustic-velocity regions, and a center region and first and second low-acoustic-velocity regions, located in the crossing region. The mass of the IDT electrode in the crossing region in the first and second end regions is smaller than the mass of the IDT electrode in the crossing region in the inner region.