Acoustic Wave Layer Structure for Bandwidth Tuning and Capacitance Retention
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Solution Overview
Problem
Existing acoustic wave devices face challenges in adjusting fractional band width while maintaining element capacitance when an additional film is added, leading to a need for increased device size.
Innovation Solution
Incorporating an intermediate layer made of the same material as the piezoelectric layer but with a smaller electromechanical coupling coefficient, allowing for easy adjustment of fractional band width without significant reduction in element capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an additional film is provided between the piezoelectric layer and functional electrodes to adjust the frequency, then the fractional band width can be adjusted, but the element capacitance reduces
Solution Approach 1:
The patent changes the material parameters of the additional film, specifically selecting materials with high dielectric constants (such as barium titanate, lead zirconate titanate, or lead magnesium nickel oxide) to increase the element capacitance. By adjusting the dielectric constant parameter of the additional film, the patent achieves both fractional band width adjustment and maintains high element capacitance, resolving the technical contradiction between these two parameters.
2Reliability
If the size of the acoustic wave device is increased to obtain a desired element capacitance, then the element capacitance can be maintained, but the device area increases
Solution Approach 1:
Instead of increasing the device area to maintain element capacitance, the patent changes the dielectric constant parameter of the additional film material. By using materials with high dielectric constants, the patent achieves the desired element capacitance within a compact device area, thus resolving the contradiction between element capacitance and device area.
Solution Approach 2:
The patent employs composite material structures where the additional film is made of high dielectric constant materials such as barium titanate, lead zirconate titanate, or lead magnesium nickel oxide. These composite material choices enable high element capacitance in a small device area, resolving the technical contradiction between capacitance and area.
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
The solution enables flexible adjustment of fractional band width and maintains element capacitance, preventing the need for larger device sizes.
Implementation Method 1
a piezoelectric layer with a first principal surface and a second principal surface opposed to each other
Implementation Method 2
an electromechanical coupling coefficient of the intermediate layer is smaller than an electromechanical coupling coefficient of the piezoelectric layer
Data Source
AI summary
An acoustic wave device includes a piezoelectric board including a piezoelectric layer with a first principal surface and a second principal surface opposed to each other, an intermediate layer on the first principal surface or the second principal surface of the piezoelectric layer, and a functional electrode on the intermediate layer. A material of the intermediate layer is a same type as a material of the piezoelectric layer, and an electromechanical coupling coefficient of the intermediate layer is smaller than an electromechanical coupling coefficient of the piezoelectric layer.