Acoustic Wave Filter Structure With Cavities for Spurious Suppression
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Solution Overview
Problem
Existing acoustic wave devices face challenges in suppressing spurious emission while maintaining electrical characteristics within the pass band, which can deteriorate filter characteristics and affect insertion loss in duplexer and multiplexer applications.
Innovation Solution
The acoustic wave device incorporates a support substrate with a piezoelectric layer and embedded second IDT electrode, featuring cavities around the electrode fingers to reduce spurious emission by leaking unnecessary waves and scattering spurious energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the acoustic wave device uses a conventional structure without cavities, then the device complexity is low, but spurious emission outside the pass band cannot be suppressed
Solution Approach 1:
The support substrate is segmented by introducing cavities that divide the continuous structure into separate regions. These cavities are positioned around the second IDT electrode and its electrode fingers, creating isolated zones that prevent spurious wave propagation while maintaining the functional integrity of the acoustic wave device.
Solution Approach 2:
The cavities act as intermediary structures between the second IDT electrode and the surrounding environment. They serve as acoustic barriers that mediate the interaction between the electrode and external waves, blocking spurious emissions without directly modifying the electrode structure itself.
2Object-generated harmful factors
If the second IDT electrode is embedded in the support without cavities, then the manufacturing process is simple, but spurious energy cannot be scattered
Solution Approach 1:
The continuous support substrate is segmented into multiple regions by the cavities, creating discrete zones around the embedded second IDT electrode. This segmentation allows spurious energy to be scattered and contained within specific regions, preventing its propagation while adding minimal complexity to the manufacturing process.
3Object-generated harmful factors
If no cavities are provided around the electrode fingers, then the structural integrity is maintained, but spurious emission outside the pass band occurs
Solution Approach 1:
The support substrate is segmented by cavities that create isolated regions around the second IDT electrode and its electrode fingers. This segmentation effectively blocks spurious emission paths while maintaining the overall structural integrity of the device through the continuous material surrounding the cavities.
Solution Approach 2:
The cavities are strategically positioned only in specific regions around the second IDT electrode and its electrode fingers, where spurious emissions originate. This localized modification provides targeted suppression of spurious emission without compromising the structural integrity of the entire 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 suppresses spurious emission across various frequency bands, enhancing the device's performance in band pass filters and other applications by maintaining optimal electrical characteristics.
Implementation Method 1
a piezoelectric layer provided on the support and including a first principal surface and a second principal surface facing each other, a first IDT electrode provided on the first principal surface
Implementation Method 2
at least one cavity is provided in a periphery of a portion of the support in which the plurality of electrode fingers of the second IDT electrode is embedded
Data Source
AI summary
An acoustic wave device includes a support including a support substrate, a piezoelectric layer provided on the support and including a first principal surface and a second principal surface facing each other, a first IDT electrode provided on the first principal surface, and a second IDT electrode provided on the second principal surface. The second IDT electrode is embedded in the support. At least one cavity is provided in a periphery of a portion of the support in which electrode fingers of the second IDT electrode is embedded.