Comb Electrode Layout for Low-Spurious Acoustic Wave Resonators
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing acoustic wave devices struggle to effectively reduce spurious emissions while maintaining a high Q factor.
Innovation Solution
The acoustic wave device incorporates a piezoelectric substrate with a pair of comb-shaped electrodes, where metal portions with a higher acoustic velocity than the electrode fingers are strategically placed between adjacent electrode fingers, alternately arranged, and designed to have a shorter length and smaller width compared to the electrode fingers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the piston mode is used to reduce spurious emissions, then spurious emissions are reduced, but there is still room for improvement in terms of reduction of spurious emissions
Solution Approach 1:
The patent applies local quality by introducing metal portions with specific acoustic velocity properties at particular locations between electrode fingers. These metal portions create localized acoustic velocity variations in the dummy region, generating acoustic impedance differences that suppress spurious emissions without affecting the overall device performance. The selective placement of materials with different acoustic properties demonstrates the local quality principle effectively.
Solution Approach 2:
The patent utilizes parameter changes by controlling the acoustic velocity of acoustic waves in the dummy region to be higher than in the central overlap region, with a specific ratio relationship (equal to or less than 1.10 times). This parameter control through material selection and geometric design creates the necessary acoustic impedance differences to reduce spurious emissions while maintaining the Q factor.
2Object-generated harmful factors
If metal portions are provided between electrode fingers to enhance acoustic velocity in dummy region, then spurious emissions are reduced, but device complexity increases
Solution Approach 1:
The patent merges the functional elements by integrating metal portions directly into the electrode structure. The metal portions are combined with the existing electrode fingers and dummy electrode fingers to form a unified comb-shaped electrode assembly. This merging approach reduces the need for separate components and simplifies the overall device structure while achieving the acoustic velocity control needed to reduce spurious emissions.
Solution Approach 2:
The metal portions serve multiple functions simultaneously: they enhance the acoustic velocity in the dummy region to reduce spurious emissions, maintain the Q factor, and integrate with the existing electrode structure. This multi-functionality reduces the need for additional components and simplifies the device 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 enhances the acoustic velocity in the dummy region, reducing spurious emissions while maintaining the desired acoustic properties, with the acoustic velocity in the dummy region being equal to or less than 1.10 times that of the central region.
Implementation Method 1
a piezoelectric substrate; and a pair of comb-shaped electrodes provided on the piezoelectric substrate
Implementation Method 2
an acoustic velocity of an acoustic wave propagating through a region where the plurality of metal portions are located being higher than an acoustic velocity of an acoustic wave propagating through a central region
Data Source
AI summary
An acoustic wave device includes a pair of comb-shaped electrodes provided on a piezoelectric substrate, each of the pair of comb-shaped electrodes including electrode fingers and metal portions that are provided between electrode fingers adjacent to each other, the metal portions having a shorter length than the electrode fingers, the electrode fingers of one comb-shaped electrode and the electrode fingers of the other comb-shaped electrode being alternately arranged at least in a part, an acoustic velocity of an acoustic wave propagating through a region where the metal portions are located being higher than an acoustic velocity of an acoustic wave propagating through a central region of an overlap region where the electrode fingers of the one comb-shaped electrode and the electrode fingers of the other comb-shaped electrode overlap, and being equal to or less than 1.10 times the acoustic velocity of the acoustic wave propagating through the central region.