Multilayer Acoustic Wave Electrode Gaps for Lower Propagation Loss
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Solution Overview
Problem
In acoustic wave devices with multilayer substrates comprising high and low acoustic velocity materials and a piezoelectric film, propagation loss increases with longer gap lengths between electrode fingers and busbars, particularly when these gaps exceed a certain length.
Innovation Solution
The acoustic wave device incorporates a multilayer substrate with a piezoelectric film, a low acoustic velocity material layer, and a high acoustic velocity material layer, where the gap lengths between electrode fingers and busbars are set to about 0.23λ or shorter, and the IDT electrode design includes specific acoustic velocity gradients and busbar structures to reduce propagation loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gap length between electrode fingers and busbar is increased, then wave guide performance is improved, but propagation loss increases
Solution Approach 1:
The patent optimizes the gap length parameter to be 0.05λ to 0.30λ (specifically 0.10λ to 0.20λ) between the electrode finger tip and busbar, which resolves the contradiction by finding the optimal range that provides sufficient wave guide performance while minimizing propagation loss. This parameter optimization allows the device to achieve both improved reliability and reduced energy loss.
2Reliability
If the gap length between electrode fingers and busbar is increased, then wave guide performance is improved, but device complexity increases
Solution Approach 1:
The patent establishes specific gap length parameters (0.05λ to 0.30λ, preferably 0.10λ to 0.20λ) that achieve wave guide performance without requiring complex structural modifications. By optimizing this single geometric parameter, the patent avoids increasing device complexity while still improving reliability.
3Speed
If the multilayer substrate structure is used, then acoustic wave propagation is enhanced, but propagation loss increases
Solution Approach 1:
The patent optimizes the gap length parameter in the multilayer substrate configuration to 0.05λ to 0.30λ, which compensates for the increased propagation loss inherent in multilayer structures. This parameter optimization maintains enhanced acoustic wave propagation speed while minimizing the energy loss that would otherwise occur in such complex substrate configurations.
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 propagation loss and prevents transverse mode ripples, improving the device's performance by confining energy within the piezoelectric film and minimizing leakage, as demonstrated by improved return loss characteristics.
Implementation Method 1
a piezoelectric film
Implementation Method 2
an acoustic velocity of an acoustic wave propagating in the piezoelectric film
Data Source
AI summary
An acoustic wave device includes a multilayer substrate including a reverse-velocity surface, a piezoelectric film, a low acoustic velocity material layer, a high acoustic velocity material layer, and an IDT electrode disposed on the piezoelectric film. In the IDT electrode, gap lengths of a first gap between a tip of each of first electrode fingers and a second busbar and a second gap between a tip of each of second electrode fingers and a first busbar are about 0.23λ or shorter, the gap lengths extending in an extension direction of the first and second electrode fingers.