SAW Resonator Electrode Layout for Transverse Mode Suppression
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Solution Overview
Problem
Surface acoustic wave resonators and filters based on single-crystal piezoelectric materials face challenges in meeting the stringent requirements of RF front-end chips due to high-frequency temperature coefficients and transverse mode ripples, leading to passband clutter and deteriorated performance.
Innovation Solution
A surface acoustic wave resonator design with an interdigital transducer featuring alternating electrode fingers and dummy electrode fingers arranged at different angles to block lateral energy leakage and suppress transverse mode ripples, utilizing a substrate layer and electrode layer with specific gap orientations and thickened portions to enhance electrical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional interdigital transducer design is used, then device structure is simple, but transverse mode ripples occur causing passband clutter and performance deterioration
Solution Approach 1:
The transducer is segmented into three distinct electrode groups (first, second, and third) with different orientation angles. This segmentation allows each group to contribute differently to the acoustic wave generation, enabling suppression of transverse mode ripples while maintaining structural feasibility. The first electrode group operates at a reference angle, the second at a larger angle, and the third at an intermediate angle, creating a distributed pattern that cancels unwanted transverse modes.
Solution Approach 2:
The patent employs asymmetric orientation angles for the three electrode groups relative to the acoustic wave propagation direction. Instead of using symmetric configurations, the first, second, and third electrode groups are oriented at different asymmetric angles (with the second group having the largest angle and the third having an intermediate angle). This asymmetric arrangement disrupts the symmetry that would otherwise allow transverse mode ripples to propagate, thereby suppressing passband clutter.
2Reliability
If single-crystal piezoelectric material is used, then Q factor is limited, but material simplicity is maintained
Solution Approach 1:
The patent employs a composite material structure consisting of a piezoelectric substrate layer combined with a specific multi-group electrode configuration. The piezoelectric substrate provides the necessary piezoelectric effect for acoustic wave generation, while the composite electrode structure (with three groups at different orientations) enhances the Q factor by suppressing transverse mode ripples. This composite approach allows the device to overcome the Q factor limitations of single-crystal piezoelectric materials alone.
3Reliability
If electrode fingers are arranged at different angles, then transverse mode ripples are suppressed, but manufacturing precision requirements increase
Solution Approach 1:
The patent utilizes parameter changes in the orientation angles of the three electrode groups to achieve transverse mode suppression. By carefully selecting and adjusting the orientation angles (with the second group at the largest angle and the third at an intermediate angle), the design optimizes the cancellation of transverse mode ripples. This parameter-based approach allows for systematic control of the acoustic wave patterns while providing clear design guidelines for manufacturing.
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 design effectively suppresses transverse mode ripples and improves electrical performance by blocking lateral energy leakage, enhancing the Q factor and overall device efficiency.
Implementation Method 1
Surface acoustic wave devices based on single-crystal piezoelectric lithium tantalate substrates have been widely used in radio frequency filters
Implementation Method 2
Surface acoustic wave resonator and surface acoustic wave filter
Data Source
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AI summary
This application relates to a surface acoustic wave resonator and a surface acoustic wave filter, including an interdigital transducer, which includes a first busbar, and first electrode fingers and first dummy electrode fingers alternately arranged and connected to the first busbar; a second busbar, and second electrode fingers and second dummy electrode fingers alternately arranged and connected to the second busbar. A first gap is provided between the first electrode finger and the second dummy electrode. A second gap is provided between the second electrode finger and the first dummy electrode finger. Each first gap is arranged along a first direction. Each second gap is arranged along a second direction. An angle between the first direction and a third direction is different from that between the second direction and the third direction. By setting the angle between the first and third direction to be different from that between the second and third direction in this application, lateral energy leakage in surface acoustic waves can be blocked, transverse mode ripples in the surface acoustic waves can be suppressed, and electrical performance can be improved.