Acoustic Wave Reflector Busbar Layout for Spurious Mode Control
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Solution Overview
Problem
Acoustic wave devices suffer from transverse-mode spurious emissions due to decreased acoustic velocity near busbars, leading to degraded filter characteristics such as insertion loss.
Innovation Solution
The acoustic wave device incorporates a piezoelectric substrate with interdigital transducers and reflectors featuring first and second high-acoustic-velocity areas, defined by specific electrode finger configurations and gaps, to maintain acoustic velocity and prevent spurious emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all electrode fingers are connected to both busbars, then electrical connectivity is ensured, but acoustic velocity decreases near the busbar causing transverse-mode spurious emissions
Solution Approach 1:
The patent applies local quality by differentiating the connection configuration of electrode fingers in different regions. Specifically, the first electrode finger connected to both busbars is positioned at one end of the reflector, while other electrode fingers are connected to only one busbar. This localized differentiation maintains electrical connectivity where needed while preventing spurious emissions in critical areas.
Solution Approach 2:
The patent segments the electrode finger connections into different groups: one electrode finger connects both busbars, while other electrode fingers connect to individual busbars. This segmentation allows the system to achieve both electrical connectivity and suppression of transverse-mode spurious emissions by distributing the connection function across multiple separately configured elements.
2Area of moving object
If electrode fingers are made thinner to reduce area, then device size is reduced, but the electrode fingers become more prone to breaking
Solution Approach 1:
The patent merges the first electrode finger with both busbars, creating a combined conductive structure. This merging provides mechanical support and electrical connectivity simultaneously, allowing the electrode finger to be thinner without compromising strength, as the busbar connection reinforces the structure.
3Ease of manufacture
If the reflector structure is simplified, then manufacturing is easier, but filter characteristics such as insertion loss are degraded
Solution Approach 1:
The patent applies local quality by implementing a simplified reflector structure in most areas while maintaining a specific configuration at critical locations. The first electrode finger connects both busbars at one end to prevent spurious emissions, while other electrode fingers have simpler single-busbar connections. This localized complexity maintains filter characteristics without significantly complicating overall 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
This configuration reduces or prevents transverse-mode spurious emissions, enhancing filter characteristics and ensuring consistent acoustic wave propagation without degradation.
Implementation Method 1
a piezoelectric substrate, an interdigital transducer electrode provided on the piezoelectric substrate
Data Source
AI summary
An acoustic wave device includes a piezoelectric substrate, an interdigital transducer electrode on the piezoelectric substrate, and two reflectors on both sides of the interdigital transducer electrode in an acoustic wave propagation direction. The reflectors include first and second busbars and first to third electrode fingers, respectively, and the first and second busbars are opposed to one another. The first busbars and the second busbars are connected by at least one third electrode finger. The reflectors each include a center area located centrally in a length direction and a first high-acoustic-velocity area that is located between the center area and the first busbars and has an acoustic velocity higher than the acoustic velocity of the center area, where the length direction is a direction in which the first to third electrode fingers extend.