Surface Acoustic Wave Device Bandwidth Adjustment
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Solution Overview
Problem
Surface acoustic wave devices utilizing leaky surface acoustic waves face challenges in adjusting band width and resonance characteristics due to increased propagation loss when varying the propagation azimuths of multiple elements, and existing solutions that adjust band width by adding capacity result in larger device sizes and higher costs.
Innovation Solution
A surface acoustic wave device with multiple elements, each featuring an IDT electrode on a piezoelectric body with a cut-angle and a confinement layer to confine the surface acoustic wave, allowing for different propagation azimuths without additional capacity, using materials like silicon nitride or aluminum nitride to minimize propagation loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the propagation azimuths of multiple surface acoustic wave elements are set to be different to adjust band width, then the band width can be adjusted, but the propagation loss increases
Solution Approach 1:
A confinement layer is introduced as an intermediary structure between the piezoelectric body and the surrounding medium. This confinement layer, made of materials with higher acoustic velocity than the surface acoustic wave, acts as a barrier that prevents energy leakage and confines the acoustic energy within the piezoelectric body, thereby reducing propagation loss while allowing azimuth variation for band width adjustment
2Adaptability or versatility
If additional capacity is added to the surface acoustic wave element to adjust band width, then the band width can be adjusted, but the device size and cost increase
Solution Approach 1:
The invention extracts the band width adjustment function from the electrical domain (capacity addition) and transfers it to the mechanical/acoustic domain (propagation azimuth variation). By controlling the propagation azimuths of surface acoustic wave elements, the effective band width can be adjusted without adding any physical capacity components, thereby maintaining compact device size while achieving the desired frequency response characteristics
3Adaptability or versatility
If additional capacity is added to the surface acoustic wave element to adjust band width, then the band width can be adjusted, but the manufacturing cost increases
Solution Approach 1:
The invention eliminates the need for additional capacity components by extracting the band width adjustment function and implementing it through geometric configuration (propagation azimuths) of existing surface acoustic wave elements. This approach reduces component count, simplifies manufacturing processes, and lowers overall device cost while maintaining the ability to adjust band width to meet different application requirements
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 device effectively adjusts band width with minimal propagation loss, maintaining a compact size and reducing costs by confining the surface acoustic wave within the piezoelectric body, enabling efficient filter and resonator performance across various frequency ranges.
Implementation Method 1
a surface acoustic wave device including a plurality of surface acoustic wave elements each of which employs a piezoelectric body
Implementation Method 2
a confinement layer which is disposed on the piezoelectric body at the side opposite to the side where the IDT electrode is disposed, and which confines the surface acoustic wave inside the piezoelectric body
Data Source
Figure 1(a)~1(b)
Figure 2~3
Figure 4~5
AI summary
A surface acoustic wave device is provided which can adjust a band width without connecting an additional capacity, and which has a sufficiently small propagation loss. In a surface acoustic wave device (1), a plurality of surface acoustic wave elements (2 and 3) are made of piezoelectric bodies (4) having the same Cut-Angle. In the surface acoustic wave elements (2 and 3), a propagation azimuth (X1) of a surface acoustic wave in at least one surface acoustic wave element (2) is different from a propagation azimuth (X2) of a surface acoustic wave in at least another one surface acoustic wave element (3). In each of the surface acoustic wave elements (2 and 3), a confinement layer (12) for confining the surface acoustic wave inside the piezoelectric body (4) is disposed on the piezoelectric body (4) at the side opposite to the side where an electrode is formed.