Acoustic Wave Element Layout to Suppress High-Frequency Ripples
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Solution Overview
Problem
Existing acoustic wave elements experience ripples at frequencies higher than their anti-resonance frequency, which affects their performance in multi-band systems.
Innovation Solution
The acoustic wave element design includes a piezoelectric layer with IDT electrodes and reflectors on both main surfaces, where the end regions of the inter-reflector region have configurations where none of the electrode fingers face each other, reducing Bragg reflection and ripples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If IDT electrodes and reflectors are formed on both main surfaces of the piezoelectric layer, then acoustic wave confinement is improved, but ripples occur at frequencies higher than the anti-resonance frequency
Solution Approach 1:
The patent applies asymmetry by making the electrode finger configurations asymmetric at the end regions of the inter-reflector region. Specifically, either none of the first electrode fingers face second electrode fingers, or none of the first reflective electrode fingers face second reflective electrode fingers in these end regions. This asymmetric design disrupts the symmetry of acoustic wave propagation paths, thereby reducing Bragg reflection and suppressing ripple formation at frequencies higher than the anti-resonance frequency, while maintaining effective acoustic wave confinement in the central region.
2Speed
If electrode fingers are configured to face each other across the piezoelectric layer, then acoustic wave transmission is improved, but Bragg reflection increases causing ripples
Solution Approach 1:
The patent extracts or removes the harmful Bragg reflection effect by configuring the end regions of the inter-reflector region such that electrode fingers do not face each other. By eliminating the facing electrode finger pairs at the boundaries, the periodic structure that causes Bragg reflection is disrupted, thereby reducing ripple formation while maintaining acoustic wave transmission through the central region where electrode fingers do face each other for efficient energy transfer.
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 design effectively reduces or prevents ripples at frequencies higher than the anti-resonance frequency, improving the acoustic wave element's performance and isolation between frequency bands.
Implementation Method 1
an acoustic wave element includes a piezoelectric layer, a first IDT electrode and a plurality of first reflectors on a first main surface of the piezoelectric layer
Implementation Method 2
The plurality of first reflectors are on both outer sides of the first IDT electrode in the first direction. Each of the plurality of first reflectors includes a plurality of first reflective electrode fingers extending in the second direction
Data Source
AI summary
An acoustic wave element includes a first IDT electrode and first reflectors on a first main surface of a piezoelectric layer and a second IDT electrode and second reflectors on a second main surface of the piezoelectric layer. When a region between the first reflectors in a first direction is a first region, a region between the second reflectors in the first direction is a second region, and a minimum region including the first and second regions as viewed in a third direction orthogonal or substantially orthogonal to the first and second directions is an inter-reflector region, in an end region of the inter-reflector region in the first direction, a region is provided in which none of the first and second electrode fingers face each other in the third direction.