IDT Width Layout in Acoustic Wave Resonators for Spurious Suppression
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Solution Overview
Problem
Existing acoustic wave resonators using Interdigital Transducers (IDTs) on piezoelectric substrates face insufficient reduction of lateral-mode spurious due to periodic variations in acoustic velocities, leading to unwanted frequency responses in high-frequency communications.
Innovation Solution
The acoustic wave resonator design incorporates alternately arranged regions with varying electrode finger widths and/or film thicknesses in the overlap region, optimizing acoustic velocities and amplitudes to concentrate energy and reduce spurious modes, ensuring a single-mode standing wave and minimizing lateral-mode spurious.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If regions with different acoustic velocities are periodically arranged at regular intervals in the overlap region, then lateral-mode spurious can be reduced, but the degree of reduction is insufficient
Solution Approach 1:
The patent applies local quality by making the electrode finger widths non-uniform within the second regions. Specifically, the outer electrode fingers have different widths than the inner electrode fingers, creating localized variations in acoustic velocity and impedance. This non-uniform distribution optimizes the suppression of lateral-mode spurious by creating a more effective acoustic velocity profile across the overlap region, thereby improving frequency response purity.
Solution Approach 2:
The patent changes the geometric parameters of the electrode fingers, specifically the widths of electrode fingers in the second regions. By varying the widths of outer versus inner electrode fingers, the patent creates controlled variations in acoustic velocity and electrical impedance. This parameter optimization enhances the suppression effect on lateral-mode spurious modes while maintaining the desired fundamental mode operation.
2Object-generated harmful factors
If electrode finger widths are made non-uniform in second regions, then acoustic energy can be concentrated and spurious modes reduced, but device complexity increases
Solution Approach 1:
The patent segments the IDT overlap region into distinct first regions and second regions with different electrode finger width characteristics. The second regions are further segmented into outer and inner portions with different widths. This segmentation allows independent optimization of each region's acoustic properties, effectively suppressing spurious modes while maintaining a structured, manufacturable design.
Solution Approach 2:
The patent introduces asymmetry by making the outer electrode fingers in the second regions have different widths than the inner electrode fingers. This asymmetric width distribution creates an optimized acoustic velocity profile that enhances suppression of lateral-mode spurious. The asymmetric design is implemented in a systematic way that maintains manufacturing feasibility.
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 lateral-mode spurious by ensuring uniform amplitude and acoustic velocity across the overlap region, enhancing the frequency response and reducing unwanted frequency components in high-frequency filters and multiplexers.
Implementation Method 1
an IDT that is located on the piezoelectric substrate and includes first regions and second regions alternately arranged in an extension direction of electrode fingers, which excite an acoustic wave
Implementation Method 2
regions with different acoustic velocities of acoustic waves are periodically arranged at regular intervals in the extension direction of the electrode fingers in the overlap region
Data Source
AI summary
An acoustic wave resonator includes: a piezoelectric substrate; and an IDT that is located on the piezoelectric substrate and includes first regions and second regions alternately arranged in an extension direction of electrode fingers, which excite an acoustic wave, in an overlap region in which the electrode fingers overlap, at least one electrode finger of the electrode fingers in the second regions having a different width from the at least one electrode finger in the first regions, a width of an outer second region of the second regions in the extension direction differs from a width of an inner second region of the second regions.