Acoustic Wave Filter Stack for Spurious Response Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing acoustic wave devices face challenges in reducing spurious responses while maintaining the main response, as providing a high acoustic velocity layer between a low acoustic velocity layer and a support substrate often degrades the main response.
Innovation Solution
Incorporating a second insulating layer with a higher acoustic velocity than the first insulating layer and a piezoelectric layer, and optimizing the thickness and acoustic velocity of these layers to confine the main acoustic wave response within the piezoelectric and insulating layers, while attenuating spurious responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a high acoustic velocity layer is provided between the low acoustic velocity layer and the support substrate to reduce spurious response, then spurious response is reduced, but main response is degraded
Solution Approach 1:
The insulating layer is divided into multiple layers (first insulating layer and second insulating layer) with different acoustic velocities. The first insulating layer has higher acoustic velocity than the piezoelectric layer to attenuate spurious waves, while the second insulating layer has lower acoustic velocity to confine main response energy, thereby resolving the contradiction between reducing spurious response and maintaining main response quality.
Solution Approach 2:
Different regions of the insulating structure are assigned different acoustic velocity characteristics. The first insulating layer (closer to substrate) has high acoustic velocity for spurious wave attenuation, while the second insulating layer (closer to piezoelectric layer) has low acoustic velocity for main response confinement. This local differentiation allows simultaneous achievement of both goals.
2Object-generated harmful factors
If the thickness of the piezoelectric layer is adjusted to be equal to or less than the wavelength to reduce spurious response, then spurious response is reduced, but device performance is compromised
Solution Approach 1:
The insulating function is segmented into multiple layers with different acoustic velocity characteristics, allowing the piezoelectric layer to maintain optimal thickness for performance while the insulating layers handle spurious response attenuation through their specific acoustic velocity properties.
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 spurious responses while maintaining or enhancing the main response by confining the acoustic energy within the desired layers, thereby improving the overall performance of the acoustic wave device.
Implementation Method 1
a first insulating layer provided between the substrate and the piezoelectric layer, the first insulating layer having an acoustic velocity of a bulk wave higher than an acoustic velocity of a bulk wave in the piezoelectric layer; and a second insulating layer provided between the first insulating layer and the piezoelectric layer, the second insulating layer having an acoustic velocity of a bulk wave higher than the acoustic velocity of the bulk wave in the first insulating layer
Data Source
AI summary
An acoustic wave device includes a substrate, a piezoelectric layer provided on the substrate, at least one pair of comb-shaped electrodes provided on the piezoelectric layer, the at least one pair of comb-shaped electrodes including a plurality of electrode fingers having an average pitch equal to or greater than 0.5 times a thickness of the piezoelectric layer, a first insulating layer provided between the substrate and the piezoelectric layer, the first insulating layer having an acoustic velocity of a bulk wave higher than an acoustic velocity of a bulk wave in the piezoelectric layer, and a second insulating layer provided between the first insulating layer and the piezoelectric layer, the second insulating layer having an acoustic velocity of a bulk wave higher than the acoustic velocity of the bulk wave in the first insulating layer.