Asymmetric IDT Electrode Layout for Acoustic Wave IMD Suppression
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Solution Overview
Problem
Existing acoustic wave devices suffer from insufficient suppression of inter-modulation distortion (IMD), which hampers the isolation of IMD from the original signal in reception frequency bands, leading to reduced reception sensitivity in mobile phones and similar devices.
Innovation Solution
The acoustic wave device incorporates a piezoelectric body layer with a crystal axis inclined in the second direction relative to its thickness direction, featuring asymmetrical configurations in the IDT electrode, including different dimensions and electrostatic capacitances in distinct regions, to reduce or prevent IMD.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional IDT electrode with symmetrical busbar configuration is used, then the device structure is simple and easy to manufacture, but the inter-modulation distortion (IMD) suppression is insufficient
Solution Approach 1:
The patent applies asymmetry by making the first and second busbars have different configurations. Specifically, the first busbar has a first width and the second busbar has a second width that is different from the first width. This asymmetric design creates different electrostatic capacitances in different regions of the IDT electrode, which suppresses inter-modulation distortion by preventing symmetric resonance modes that generate IMD.
Solution Approach 2:
The patent implements local quality by varying the width of busbars at different positions. The first busbar has a first width in a first region and a second width in a second region, while the second busbar has corresponding width variations. This local variation in geometric properties creates region-specific electrostatic characteristics that suppress IMD while maintaining overall device functionality.
2Reliability
If the busbar width is uniform across all regions, then the manufacturing process is simpler, but the electrostatic capacitance distribution is non-optimal for IMD suppression
Solution Approach 1:
The patent divides the busbar structure into multiple regions with different width specifications. The first busbar has a first width in a first region and a second width in a second region, creating localized electrostatic capacitance variations. This allows precise control of electromagnetic field distribution in different areas to suppress IMD while maintaining manufacturability through standardized fabrication processes.
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 design effectively reduces or prevents IMD, enhancing the reception sensitivity of mobile phones and similar devices by ensuring asymmetric electrostatic capacitances and acoustic velocities across the IDT electrode regions, thereby minimizing interference.
Implementation Method 1
an acoustic wave device includes a piezoelectric body layer having a crystal axis
Implementation Method 2
an IDT electrode on the piezoelectric body layer
Data Source
AI summary
An acoustic wave device includes a piezoelectric body layer having a crystal axis and an IDT electrode on the piezoelectric body layer. When an acoustic wave propagation direction is a first direction and an orthogonal or substantially orthogonal direction is a second direction, the crystal axis of the piezoelectric body layer is inclined in the second direction with respect to a thickness direction. The IDT electrode includes first and second busbars that oppose each other, and first and second electrode fingers and each including one end connected to any one of the first and second busbars. A region where the adjacent electrode fingers overlap each other in the first direction is a cross region which includes a central region positioned on a center side in the second direction, and first and second edge regions that oppose each other with the central region interposed therebetween in the second direction.