Dual-Sided IDT Layout for Compact Acoustic Wave Devices
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Solution Overview
Problem
Existing acoustic wave devices face challenges in reducing size due to the need for space for opposite-phase wiring between IDT electrodes on both main surfaces, leading to capacitance issues that degrade device characteristics.
Innovation Solution
The design includes IDT electrodes on both main surfaces of a piezoelectric layer with opposing polarities and overlapping electrode fingers, eliminating the need for external wiring and reducing capacitance between electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If wiring is extended from both main surfaces in opposite directions to drive IDT electrodes in opposite phases, then the IDT electrodes can be driven in opposite phases, but the device size increases due to the required wiring space
Solution Approach 1:
The patent combines the wiring paths by having both IDT electrodes share common busbars on the same main surface. The first IDT electrode has first and second busbars, and the second IDT electrode also has first and second busbars that overlap with those of the first IDT electrode. This merging of wiring structures eliminates the need for separate wiring extensions in opposite directions, thereby reducing device size while maintaining opposite-phase driving capability.
2Area of stationary object
If busbars of IDT electrodes on both main surfaces are made to match or overlap, then wiring space is reduced, but capacitance is generated between the two IDT electrodes which degrades characteristics
Solution Approach 1:
The patent segments the busbars into distinct first busbars and second busbars with different potential polarities. The first IDT electrode has first and second busbars with opposite potentials, and the second IDT electrode similarly has first and second busbars with opposite potentials. This segmentation ensures that overlapping busbars do not generate harmful capacitance while still achieving compact wiring layout.
3Ease of operation
If IDT electrodes on both main surfaces are driven in opposite phases using traditional wiring, then opposite-phase operation is achieved, but the device complexity increases due to extended wiring requirements
Solution Approach 1:
The patent merges the wiring structures of both IDT electrodes by having them share common busbar locations on the same main surface. The first IDT electrode and second IDT electrode both have their busbars positioned to overlap, with connections made through the piezoelectric layer. This unified wiring approach simplifies the overall device structure while enabling opposite-phase operation through the polarity arrangement of the shared busbars.
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 allows for a reduction in device size while minimizing characteristic degradation, enhancing resonance characteristics and enabling smaller, more efficient acoustic wave devices.
Implementation Method 1
a piezoelectric layer 6... The piezoelectric layer includes first and second main surfaces 6a and 6b facing each other
Implementation Method 2
a first IDT electrode 7 on the first main surface 6a of the piezoelectric layer 6 and a second IDT electrode 8 on the second main surface 6b
Data Source
AI summary
An acoustic wave device includes a first IDT electrode on a first main surface of a piezoelectric layer, and a second IDT electrode on a second main surface of the piezoelectric layer. The first IDT electrode includes first and second electrode fingers. The second IDT electrode includes third and fourth electrode fingers. The first and fourth electrode fingers overlap each other with the piezoelectric layer interposed therebetween. The second and third electrode fingers overlap each other with the piezoelectric layer interposed therebetween. A potential of the first electrode finger and that of the fourth electrode finger are opposite to each other. A potential of the second electrode finger and that of the third electrode finger are opposite to each other.