Acoustic Wave Filter Layout for Suppressing Transverse Modes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing acoustic wave devices using bulk waves in a thickness shear mode experience deterioration in loss when a mass addition film is provided in the edge and gap regions, leading to the generation of unnecessary waves near resonant and anti-resonant frequencies.
Innovation Solution
The acoustic wave device incorporates a piezoelectric substrate with a lithium niobate piezoelectric layer and an IDT electrode, featuring a strip-shaped mass addition film in the gap regions and granular mass addition films in the edge and gap regions, carefully designed to overlap electrode fingers and suppress transverse modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a mass addition film is provided in the edge region and gap region, then deterioration in loss is suppressed, but unnecessary waves are generated in the vicinity of resonant frequency and anti-resonant frequency
Solution Approach 1:
The mass addition film is segmented into two distinct types: a strip-shaped mass addition film in the gap region and granular mass addition films in the edge region. This segmentation allows each type to perform its specific function - the strip-shaped film suppresses loss in the gap region while the granular films suppress transverse modes and unnecessary waves in the edge region, resolving the contradiction between loss suppression and unwanted wave generation.
Solution Approach 2:
Different regions are assigned different mass addition film configurations tailored to their specific needs. The gap region receives a strip-shaped film for loss suppression, while the edge region receives granular films for transverse mode suppression. This local differentiation ensures that each region's mass addition film configuration optimally addresses the specific acoustic challenges of that region without generating unnecessary waves.
2Object-generated harmful factors
If granular mass addition films are provided in the edge region, then transverse modes are suppressed, but device complexity increases
Solution Approach 1:
The harmful transverse modes are extracted and suppressed by introducing granular mass addition films specifically in the edge regions. These granular films are strategically placed to target and eliminate transverse mode vibrations without affecting the primary acoustic wave propagation in the gap region, thereby suppressing harmful factors while maintaining overall device functionality.
Solution Approach 2:
The physical configuration of the mass addition film is changed from a continuous strip shape to discrete granular particles in the edge region. This parameter change in film morphology allows the edge region to suppress transverse modes effectively while the granular structure can be optimized for ease of deposition and manufacturing, balancing performance with fabrication simplicity.
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 unnecessary waves near resonant and anti-resonant frequencies, even with mass addition films in the edge and gap regions, thereby improving the device's performance and suppressing transverse modes.
Implementation Method 1
A piezoelectric layer is provided on a support body. A pair of electrodes are provided on the piezoelectric layer. The pair of electrodes face each other on the piezoelectric layer, and are connected to mutually different potentials. An alternating current (AC) voltage is applied between the electrodes to excite the bulk wave in the thickness shear mode.
Implementation Method 2
the piston mode is established by forming a plurality of regions having different acoustic velocities in the direction in which the plurality of electrode fingers extend. In this manner, a transverse mode is suppressed.
Data Source
AI summary
An acoustic wave device includes a piezoelectric substrate including a support including a support substrate and a piezoelectric film on the support and including a piezoelectric layer, and an IDT electrode on the piezoelectric layer and including first and second busbars and first and second electrode fingers. An acoustic reflection portion is in the support overlapping the IDT electrode. When a thickness of the piezoelectric film is d and a center-to-center distance between the adjacent electrode fingers is p, d/p is about 0.5 or smaller. When viewed in an electrode finger orthogonal direction, a region in which the adjacent electrode fingers overlap each other is an intersecting region. A region between the intersecting region and the first and second busbars includes first and second gap regions. The intersecting region includes a central region and first and second edge regions extending across the central region in the electrode finger extending direction.