Acoustic Wave Electrode Structure for Compact Low-Resistance Filters
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Solution Overview
Problem
Acoustic wave devices used in filters, particularly those employing a thickness-shear mode bulk wave, face challenges in miniaturization and high electrical resistance, which affect the size and efficiency of the filter devices.
Innovation Solution
The acoustic wave device incorporates a piezoelectric layer with a specific configuration of comb-shaped electrodes and a reference potential electrode, featuring multiple potential connection portions and a meandering shape, to reduce electrical resistance and enable miniaturization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electrostatic capacitance of the acoustic wave resonator is increased to obtain good characteristics in the ladder filter, then the filter characteristics are improved, but the acoustic wave resonator needs to be increased in size, causing the ladder filter to be increased in size
Solution Approach 1:
The electrode connected to reference potential is divided into multiple segments (first through fourth electrodes) arranged in a specific sequence between the input and output electrodes. This segmentation allows the reference potential electrode to be distributed throughout the structure, increasing its effective area and electrostatic capacitance without requiring an overall increase in device size.
Solution Approach 2:
The electrode structure transitions from a simple linear arrangement to a multi-dimensional interdigitated configuration. The electrodes are arranged in a specific sequence (input, reference, output, reference) with overlapping finger structures, utilizing both lateral and vertical dimensions to maximize capacitance within a compact footprint.
2Volume of moving object
If the reference potential electrode is provided between the input and output electrodes to obtain suitable filter waveform without increasing size, then the filter device size is reduced, but the electrical resistance of the reference potential electrode easily becomes high
Solution Approach 1:
The reference potential electrode is segmented into multiple separate electrodes (first through fourth) distributed between the input and output electrodes. Each segment is connected to the reference potential, creating multiple parallel conduction paths that reduce the overall electrical resistance while maintaining the compact structure.
Solution Approach 2:
Multiple reference potential electrodes are combined in parallel, all connected to the same reference potential. This merging of multiple conduction paths reduces the equivalent resistance of the reference potential electrode structure, solving the high resistance problem while keeping the device size small.
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 the achievement of suitable filter waveforms without increasing the size of the filter device, while also reducing the electrical resistance of the acoustic wave device, thereby enhancing its performance and miniaturization potential.
Implementation Method 1
a piezoelectric layer is provided on a support. A pair of electrodes are provided on the piezoelectric layer. The pair of electrodes face each other on the piezoelectric layer and are connected to different potentials. An AC voltage is applied between the electrodes to excite bulk waves in the thickness-shear mode.
Data Source
AI summary
An acoustic wave device includes a piezoelectric layer, first and second comb-shaped electrodes respectively including first and second busbars and first and second electrode fingers connected to the first and second busbars, and connected to input and output potentials, and a reference potential electrode including third electrode fingers aligned with the first and second electrode fingers in a direction in which the first and second electrode fingers are arranged, and connection electrodes connecting adjacent third electrode fingers, the reference potential electrode being at least partially provided between the first and second comb-shaped electrodes and connected to a reference potential. Starting from the first electrode finger, the first electrode finger, the third electrode finger, the second electrode finger, and the third electrode finger define one period. The reference potential electrode includes at least three potential connection portions connected to the reference potential.