Acoustic Wave Resonator Electrode Layout for Higher Capacitance
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Solution Overview
Problem
Existing acoustic wave devices face challenges in achieving high electrostatic capacitance without increasing size, particularly in ladder filters using bulk wave thickness shear mode resonators, and struggle with insufficient electric power handling capability.
Innovation Solution
The acoustic wave device incorporates first and second acoustic wave resonators with comb-shaped electrodes and a third electrode, arranged in a specific pattern to enhance electrostatic capacitance and power handling, utilizing lithium niobate piezoelectric layers and interdigitated finger configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the size of acoustic wave resonators is increased to raise electrostatic capacitance, then the electrostatic capacitance is improved, but the size of the ladder filter is enlarged
Solution Approach 1:
The patent introduces a third electrode connected to reference potential between the input and output electrodes, segmenting the electrode structure into multiple functional regions. This segmentation allows the resonator to achieve higher electrostatic capacitance through the additional electrode interactions without requiring an increase in the overall resonator size, thereby preventing enlargement of the ladder filter.
Solution Approach 2:
The patent utilizes the thickness dimension of the piezoelectric layer by providing electrodes on opposite surfaces and incorporating a third electrode structure that extends through the thickness direction. This dimensional approach increases the electrostatic capacitance by creating additional capacitive pathways without expanding the planar footprint of the resonator.
2Device complexity
If a simple electrode configuration is used, then the device complexity is reduced, but the electric power handling capability is insufficient
Solution Approach 1:
The electrode structure is segmented into first electrodes connected to input potential, second electrodes connected to output potential, and third electrodes connected to reference potential. This segmentation creates multiple independent electrical pathways that distribute the power handling load, enabling the resonator to handle higher electric power while maintaining a relatively simple planar electrode layout.
Solution Approach 2:
The third electrode connected to reference potential acts as an intermediary between the input and output electrodes, providing an additional electrical pathway that mediates the power flow. This intermediary structure enhances the electric power handling capability by distributing the electrical stress across multiple pathways without significantly increasing the overall device complexity.
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 reduced filter apparatus size and improved electric power handling capability, while maintaining effective filter performance.
Implementation Method 1
a piezoelectric layer made of lithium niobate... With the application of an AC voltage to between these electrodes, a bulk wave of the thickness shear mode is excited
Data Source
AI summary
An acoustic wave device includes first and second acoustic wave resonators. Each of the first and second acoustic wave resonators includes a piezoelectric film including a piezoelectric layer, first and second comb-shaped electrodes, and a third electrode. The first comb-shaped electrode includes a first busbar and first electrode fingers. The second comb-shaped electrode includes a second busbar and second electrode fingers. The third electrode includes third electrode fingers and a connection electrode. The third electrode fingers are arranged side by side with the first and second electrode fingers. The connection electrode connects adjacent third electrode fingers. An arrangement order of the first, second, and third electrode fingers is the first electrode finger, the third electrode finger, the second electrode finger, and the third electrode finger repeated as one period. Each of the first and second acoustic wave resonators is a divided resonator including an acoustic wave resonator divided in series.