Curved Acoustic Reflection Layer for Elastic Wave Devices
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Solution Overview
Problem
Elastic wave devices with acoustic reflection layers suffer from degradation of resonance and filter characteristics due to the reflection of unwanted waves, which are not effectively suppressed by existing designs.
Innovation Solution
The elastic wave device incorporates a piezoelectric layer with an acoustic reflection layer featuring high and low acoustic impedance layers, where the outer peripheral edges of these layers are curved or separated by a step to reduce unwanted wave reflection, thereby minimizing their impact on the piezoelectric layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If an acoustic reflection layer is provided to increase elastic wave excitation efficiency, then the excitation efficiency of elastic waves is improved, but unwanted waves are also reflected which degrades resonance characteristics and filter characteristics
Solution Approach 1:
The acoustic reflection layer is designed with spatially varying properties: the outer peripheral edges of the high and low acoustic impedance layers are curved so that they do not lie within the surfaces where the individual main surfaces at a center are extended. This creates local variations in acoustic impedance distribution, allowing the center region to effectively reflect unwanted waves while the curved peripheral edges reduce harmful reflections that would otherwise degrade resonance characteristics.
2Ease of manufacture
If a simple laminated structure of high and low acoustic impedance layers is used, then manufacturing is simplified, but unwanted wave reflection is not sufficiently suppressed
Solution Approach 1:
The outer peripheral edges of the high and low acoustic impedance layers are designed with curved surfaces rather than flat surfaces. Specifically, the curved edges are positioned so they do not lie within the extended surfaces of the main surfaces at the center. This curvature modifies the reflection characteristics of unwanted waves, reducing harmful reflections while maintaining the simple laminated structure for ease of manufacture.
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 design significantly reduces or prevents the reflection of unwanted waves back to the piezoelectric layer, thereby maintaining the integrity of resonance and filter characteristics in elastic wave devices.
Implementation Method 1
An elastic wave device including an acoustic reflection layer is capable of causing elastic waves leaking from a piezoelectric layer side to the acoustic reflection layer side to be reflected toward the piezoelectric layer side by the acoustic reflection layer
Implementation Method 2
an IDT electrode is formed on one main surface of a piezoelectric layer
Data Source
AI summary
An elastic wave device in which an IDT electrode defines an excitation electrode on a piezoelectric layer, an acoustic reflection layer is laminated on a first main surface of the piezoelectric layer, the acoustic reflection layer includes high acoustic impedance layers with a relatively high acoustic impedance and low acoustic impedance layers with a relatively low acoustic impedance, and the acoustic reflection layer has an unwanted wave reflection suppression structure in which reflection of unwanted waves toward the piezoelectric layer side is significantly reduced or prevented.