Sloped Multilayer Piezoelectric Structure for Multi-Band SAW Filters
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Solution Overview
Problem
Current multilayer piezoelectric substrate (MPS) surface acoustic wave (SAW) devices face challenges in achieving optimal electrical properties such as coupling factor k2 and temperature coefficient of frequency (TCF) across multiple frequency bands, due to the limitations of single piezoelectric layer configurations.
Innovation Solution
The implementation of a multilayer piezoelectric substrate with multiple piezoelectric layers of varying thicknesses and cut angles, including a lithium tantalate and lithium niobate configuration, where the second piezoelectric layer is thinner and has a different cut angle, enhances the coupling factor k2 and allows for improved temperature coefficient tuning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single piezoelectric layer configuration is used, then the device structure is simple, but the coupling factor k2 and temperature coefficient cannot be optimized across multiple frequency bands
Solution Approach 1:
The piezoelectric layer is segmented into multiple distinct layers (first piezoelectric layer and second piezoelectric layer), each with different thicknesses and material compositions. This segmentation allows each layer to contribute differently to the acoustic wave generation, enabling optimization of coupling factor and temperature coefficient across multiple frequency bands while maintaining a manageable structural complexity.
Solution Approach 2:
Different regions of the piezoelectric structure are assigned different local qualities through varying the thickness and material composition of each piezoelectric layer. The first piezoelectric layer has a first thickness and the second piezoelectric layer has a second thickness different from the first, creating local variations that enable frequency-selective optimization of electrical properties at different locations within the device.
2Reliability
If multiple piezoelectric layers with varying thicknesses are used, then the coupling factor k2 is enhanced, but the manufacturing process becomes more complex
Solution Approach 1:
The invention changes key parameters of the piezoelectric layers, specifically the thickness and material composition, to optimize electrical properties. By systematically varying the thickness of each piezoelectric layer and selecting appropriate materials with different piezoelectric coefficients, the coupling factor k2 is enhanced while maintaining manufacturability through controlled parameter variations rather than uncontrolled complexity.
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 improves the coupling factor k2 while maintaining low loss and suitable temperature coefficient of frequency, enabling the SAW device to operate effectively across multiple frequency bands with enhanced electrical properties.
Implementation Method 1
a piezoelectric structure including a first region having a first thickness, a second region having a second thickness different from the first thickness, and a third region sloped between the first region and the second region; a first surface acoustic wave element positioned in the first region; and a second surface acoustic wave element positioned in the second region
Data Source
AI summary
A surface acoustic wave device is disclosed. The surface acoustic wave device can include a support substrate, a piezoelectric structure that includes a first region having a first thickness, a second region having a second thickness different from the first thickness, and a third region sloped between the first region and the second region, a first surface acoustic wave element that is positioned in the first region, and a second surface acoustic wave element that is positioned in the second region.