Elastic Wave Resonator Layout for High-Frequency A1 Lamb Waves
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Solution Overview
Problem
Existing elastic wave devices face challenges in achieving resonance at high frequencies relative to the pitch of electrode fingers, limiting their operational frequency range.
Innovation Solution
The elastic wave device incorporates a piezoelectric layer with a thickness less than 1.5 times the pitch of the electrode fingers and an IDT electrode design featuring first and second busbars connected to different potentials, with electrode fingers that have a wide portion extending to overlap the tip ends of adjacent fingers, facilitating the propagation of A1-mode Lamb waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the piezoelectric layer thickness is increased to achieve high frequency resonance, then the resonant frequency increases, but the device complexity and manufacturing precision requirements increase
Solution Approach 1:
The patent changes the thickness parameter of the piezoelectric layer to be less than 1.5 times the electrode finger pitch, which is a specific parameter relationship that enables high frequency resonance while controlling manufacturing complexity. This parameter optimization resolves the contradiction by establishing a clear design rule.
2Speed
If the electrode finger pitch is decreased to achieve higher resonant frequency, then the resonant frequency increases, but the manufacturing precision and device complexity increase
Solution Approach 1:
The patent establishes a parameter relationship where the piezoelectric layer thickness is controlled relative to the electrode finger pitch (thickness < 1.5 × pitch). This relative parameter control allows achieving high frequency resonance without requiring absolutely small pitch dimensions, thereby reducing manufacturing precision requirements.
3Manufacturing precision
If the piezoelectric layer thickness is reduced to simplify manufacturing, then the manufacturing precision requirements decrease, but the resonant frequency may be limited
Solution Approach 1:
The patent optimizes the piezoelectric layer thickness to be greater than zero but less than 1.5 times the electrode finger pitch. This optimized parameter range achieves a balance where the thickness is sufficient to support high frequency resonance (including 5 GHz as mentioned in the summary) while remaining thin enough to simplify manufacturing processes compared to conventional thicker designs.
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 enables resonance at higher frequencies, such as 5 GHz, with reduced spurious frequencies and increased phase characteristics, while minimizing loss and leakage, thereby enhancing the device's performance.
Implementation Method 1
an elastic wave device that applies a voltage to an interdigital transducer (IDT) electrode on a piezoelectric body to generate an elastic wave that propagates through the piezoelectric body
Implementation Method 2
a standing wave of an elastic wave having a wavelength that is twice the pitch of the electrode fingers is formed, and the frequency of this standing wave serves as a resonant frequency
Implementation Method 3
The acoustic reflection layer is formed of low acoustic impedance layers and high acoustic impedance layers that are alternately stacked. This configuration makes it possible to provide an elastic wave device having a resonant point at 5 GHz even when the electrode fingers have a period of about 3 μm
Data Source
AI summary
An elastic wave device includes a substrate, a multilayer film located on the substrate, a piezoelectric layer located on the multilayer film, and an IDT electrode located on the piezoelectric layer. The IDT electrode includes electrode fingers each having a large width from a portion connected to a busbar to a position overlapping tip ends of the other electrode fingers when viewed in an arrangement direction of the electrode fingers.