Asymmetric Electrode Acoustic Wave Resonator for Spurious Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing acoustic wave devices using LiNbO3 or LiTaO3 face challenges in reducing size while maintaining a high Q value and controlling spurious responses.
Innovation Solution
The use of a piezoelectric layer made of lithium niobate or lithium tantalate with electrodes having different sectional shapes in a direction orthogonal to their longitudinal direction, and a thickness-to-distance ratio (d/p) of about 0.5 or less, facilitates bulk waves in a thickness shear primary mode, allowing for size reduction without significant Q value decrease and controlling spurious responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the number of electrode fingers is reduced to achieve size reduction, then the device size is reduced, but the Q value decreases and spurious responses are generated
Solution Approach 1:
The patent applies asymmetry by configuring electrodes with different widths (first electrode width ≠ second electrode width) rather than using symmetric identical electrodes. This asymmetric electrode configuration modifies the acoustic wave excitation pattern, enabling size reduction while maintaining high Q value and suppressing spurious responses that would otherwise occur with reduced electrode numbers.
Solution Approach 2:
The patent changes key parameters including the width ratio between first and second electrodes, the pitch between adjacent electrodes, and the thickness-to-pitch ratio (d/p ≤ 0.5). By optimizing these parameters, the device achieves high Q value and suppressed spurious responses even with reduced electrode finger counts, resolving the contradiction between size reduction and performance maintenance.
2Volume of moving object
If the number of electrode fingers is reduced to achieve size reduction, then the device size is reduced, but spurious responses are generated on resonance characteristics
Solution Approach 1:
The asymmetric electrode configuration (different widths for first and second electrodes) creates a specific acoustic excitation pattern that suppresses spurious responses. This asymmetry modifies the resonance characteristics to eliminate harmful spurious responses that would normally appear when reducing the number of electrode fingers for size reduction.
Solution Approach 2:
By optimizing parameters including the width ratio between electrodes, pitch between electrodes, and thickness-to-pitch ratio (d/p ≤ 0.5), the patent suppresses spurious responses while maintaining compact device size. These parameter changes fundamentally alter the resonance behavior to eliminate harmful effects.
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 maintains a high Q value and effectively controls the magnitude and position of spurious responses, achieving improved resonance characteristics even with reduced electrode pairs.
Implementation Method 1
an acoustic wave device according to a preferred embodiment of the present invention includes a piezoelectric layer made of lithium niobate or lithium tantalate
Data Source
AI summary
An acoustic wave device includes a piezoelectric layer made of lithium niobate or lithium tantalate, and at least one pair of electrodes opposed to each other in a direction intersecting a thickness direction of the piezoelectric layer. When d is a thickness of the piezoelectric layer and p is a distance between centers of electrodes adjacent to each other in the at least one pair of electrodes, d/p is about 0.5 or less. The at least one pair of electrodes extend in a longitudinal direction and includes a first electrode and a second electrode with sectional shapes different from each other in any cross section in a direction orthogonal or substantially orthogonal to the longitudinal direction of the at least one pair of electrodes.