Acoustic Wave Layer Structure for Wideband Higher-Order Mode Reduction
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Solution Overview
Problem
Existing acoustic wave devices are not effective in reducing higher order modes across a wide band, limiting their performance in applications such as filters for mobile phones.
Innovation Solution
The acoustic wave device incorporates a crystal substrate with a silicon carbide layer and a lithium tantalate layer, along with an interdigital transducer electrode, which reduces higher order modes by leveraging the lower velocity of bulk waves in the crystal substrate compared to surface acoustic waves in the lithium tantalate layer, thereby enhancing frequency stability and reducing spurious modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional acoustic wave device structure is used, then the device can operate, but it cannot effectively reduce higher order modes across a wide band
Solution Approach 1:
The patent employs a composite structure consisting of a crystal substrate, a silicon carbide layer, and a lithium tantalate layer. This multi-material configuration allows the device to reduce higher order modes across a wide frequency band by leveraging the complementary properties of each material, resolving the contradiction between mode reduction effectiveness and wide band adaptability
Solution Approach 2:
The patent utilizes the velocity difference parameter between bulk waves in the crystal substrate and surface acoustic waves in the lithium tantalate layer. By carefully selecting materials and controlling wave velocity parameters, the device achieves effective higher order mode reduction while maintaining wide band operational capability
2Speed
If the bulk wave velocity in the crystal substrate is increased, then the device operates faster, but higher order modes cannot be effectively reduced
Solution Approach 1:
The patent explicitly controls the bulk wave velocity parameter in the crystal substrate to be lower than the surface acoustic wave velocity in the lithium tantalate layer. This parameter selection is critical for achieving higher order mode reduction while maintaining appropriate operational speed for the device
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 higher order modes across a wide band, improving the frequency stability and performance of acoustic wave devices, including filters, by ensuring that the bulk waves in the crystal substrate have a lower velocity than the surface acoustic waves in the lithium tantalate layer, thus enhancing the device's operational range and efficiency.
Implementation Method 1
an interdigital transducer electrode on the lithium tantalate layer
Implementation Method 2
surface acoustic waves in the lithium tantalate layer
Implementation Method 3
bulk waves in the crystal substrate have a lower velocity than the surface acoustic waves
Data Source
AI summary
An acoustic wave device includes a crystal substrate, a silicon carbide layer on the crystal substrate, a lithium tantalate layer on the silicon carbide layer, and an interdigital transducer electrode on the lithium tantalate layer and including multiple first and second electrode fingers.