Curved IDT Electrode Layout for Suppressing Acoustic Spurious Responses
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Solution Overview
Problem
Existing acoustic wave devices suffer from insufficient reduction or prevention of spurious responses due to electrode finger pitch variations in the central and end portions of the interdigital transducer (IDT) electrode.
Innovation Solution
The acoustic wave device incorporates a piezoelectric substrate with an IDT electrode featuring a pair of busbars and interdigitated electrode fingers, where the overlap region includes at least one curved-line region with non-constant curvature, allowing for varying excitation angles and electrode finger pitches to disperse spurious waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electrode finger pitch is made smaller in the central portion than in the end portions, then the resonance characteristics are improved, but spurious responses cannot be reduced or prevented sufficiently
Solution Approach 1:
The patent applies curvature to the electrode fingers by making them follow a curved line from the center of the overlap region to the common electrodes, rather than straight lines. This curved configuration disperses spurious waves in different directions and prevents them from constructively interfering, thereby reducing spurious responses while maintaining good resonance characteristics through proper pitch variation along the curved path.
Solution Approach 2:
The patent implements different electrode finger pitch values in different regions: a first pitch value in the central portion of the overlap region and a second pitch value in the end portions. This local variation in pitch allows optimization of resonance characteristics in the central region while the curved configuration in end regions helps suppress spurious responses, achieving both goals simultaneously through region-specific design.
2Object-generated harmful factors
If a curved line configuration is applied to electrode fingers, then spurious waves are dispersed, but the device complexity increases
Solution Approach 1:
The electrode fingers are configured to follow a curved line from the center of the overlap region to the common electrodes. This curvature disperses spurious waves generated during operation, preventing them from concentrating and causing interference. The curved path is designed to be smooth and continuous, which while more complex than straight lines, provides effective spurious wave suppression without excessive complexity.
Solution Approach 2:
The patent varies the pitch parameter along the curved path of the electrode fingers, using a first pitch value in the central portion and a second pitch value in the end portions. This parameter variation along the curved configuration allows optimization of both resonance characteristics and spurious wave suppression, managing the complexity through systematic parameter control rather than arbitrary design.
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 reduces or prevents spurious waves by ensuring uniform resonant and anti-resonant frequencies across the overlap region, enhancing resonance characteristics and reducing spurious responses.
Implementation Method 1
a piezoelectric substrate including a piezoelectric layer, and an IDT electrode on the piezoelectric layer
Implementation Method 2
The at least one curved-line region includes a curved-line region one edge of which corresponds to the first envelope. In the curved-line region, each of the plurality of first electrode fingers and the plurality of second electrode fingers has a non-constant curvature.
Data Source
AI summary
An acoustic wave device includes a piezoelectric substrate including a piezoelectric layer, and an IDT electrode on the piezoelectric layer and including first and second busbars and first and second electrode fingers. Virtual lines connecting tips of distal end portions of the first and second fingers are respectively referred to as first and second envelopes. An overlap region is between the first and second envelopes and includes at least one curved-line region, in which the first and second electrode fingers have a curved plan-view shape. In the curved-line region, each of the first and second electrode fingers has a non-constant curvature.