Acoustic Mirror Interface Roughness for Spurious Mode Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Acoustic wave devices suffer from spurious responses caused by mirror modes, which affect filter characteristics due to wave modes locked in the acoustic mirror, particularly in the frequency band around 1.6 times or larger than the resonant frequency.
Innovation Solution
The acoustic wave device incorporates a support substrate with an acoustic reflection film comprising alternately stacked high and low acoustic impedance layers, where the interface between these layers has irregularities, effectively scattering the mirror mode and preventing spurious responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional acoustic mirror with smooth interfaces is used, then the device structure is simple, but spurious responses occur due to mirror mode locking
Solution Approach 1:
The acoustic reflection film is segmented into multiple alternating high and low acoustic impedance layers, creating a multilayer structure that prevents mirror mode locking. This segmentation disrupts the uniform acoustic path that causes spurious responses in conventional single-layer mirrors.
Solution Approach 2:
The interface between acoustic impedance layers is given local quality through intentional irregularities or roughness. This local structural variation at the interfaces scatters mirror mode waves and prevents the coherent locking that causes spurious responses, while maintaining the overall multilayer architecture.
2Reliability
If irregularities are introduced at the layer interfaces, then spurious responses are reduced, but manufacturing precision requirements increase
Solution Approach 1:
The interface irregularities are controlled within specific parameter ranges (arithmetic mean roughness Ra between 0.01-1.0 μm, and height differences h between 0.01-0.5 μm). By defining these parameter boundaries, the invention balances spurious response suppression with manufacturability, ensuring the irregularities are sufficient to scatter mirror modes but not so extreme as to make manufacturing prohibitively difficult.
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 or prevents spurious responses by scattering the mirror mode without affecting the main mode characteristics, enhancing the performance of the acoustic wave device.
Implementation Method 1
The interface between the layers of the first and second materials includes irregularities... effectively scattering the mirror mode and preventing spurious responses
Implementation Method 2
The acoustic mirror is a multilayer body formed by alternating layers of two materials, one having a low acoustic impedance and the other having a high acoustic impedance
Implementation Method 3
This acoustic wave device has a piezoelectric layer and an electrode on each of the layer's two primary surfaces. The piezoelectric layer and the electrodes form a piezoelectric element
Data Source
AI summary
An acoustic wave device includes a support substrate, an acoustic reflection film on the support substrate, a piezoelectric layer on the acoustic reflection film, the piezoelectric layer including first and second primary surfaces, and first and second flat-plate electrodes on the first and second primary surfaces of the piezoelectric layer. The acoustic reflection film includes high acoustic impedance layers and low acoustic impedance layers alternately stacked together. At least one layer of the high acoustic impedance and low acoustic impedance layers is a stack of layers of first and second materials having equal or substantially equal acoustic impedances for at least one of longitudinal acoustic impedance and transversal acoustic impedance. The interface between the layers of first and second materials has irregularities.