Acoustic Wave Resonator Electrode Layout for Compact Filter Waveforms
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Solution Overview
Problem
Acoustic wave devices using bulk waves in thickness-shear mode face challenges in achieving favorable filter waveforms without increasing the size of the ladder filter, as they require larger electrostatic capacitance, leading to larger device sizes.
Innovation Solution
The acoustic wave device incorporates a piezoelectric layer with first, second, and third electrode fingers, where the third electrode finger overlaps with facing regions, allowing for efficient excitation of bulk waves in thickness-shear mode without increasing the device size, enabling favorable filter waveforms with a single or small number of resonators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electrostatic capacitance of acoustic wave resonators is increased to obtain favorable filter waveforms, then the filter performance is improved, but the ladder filter size increases
Solution Approach 1:
The patent introduces a third electrode finger that overlaps with the facing region between first and second electrode fingers, adding a vertical dimension to the electrode structure. This three-dimensional electrode arrangement increases electrostatic capacitance without expanding the planar footprint of the resonator, thereby improving filter waveform quality while maintaining compact filter size.
Solution Approach 2:
The patent modifies the electrode configuration by adding a third electrode finger connected to reference potential that overlaps with the facing region. This structural parameter change increases the electrostatic capacitance of the resonator, enabling favorable filter waveforms to be achieved with smaller device dimensions.
2Quantity of substance
If the size of acoustic wave resonator is increased to increase electrostatic capacitance, then the electrostatic capacitance is improved, but the device complexity increases
Solution Approach 1:
Instead of increasing resonator size in the planar direction, the patent adds a third electrode finger that overlaps vertically with the facing region between first and second electrode fingers. This dimensional approach increases electrostatic capacitance without proportionally increasing structural complexity, as the added electrode integrates into the existing resonator architecture.
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 attainment of favorable filter waveforms and reduced device size by effectively utilizing the piezoelectric layer's electrostatic capacitance, maintaining the compactness of the filter device while enhancing its performance.
Implementation Method 1
A bulk wave in thickness-shear mode is excited by application of alternating-current voltage between the above-described electrodes
Data Source
AI summary
An acoustic wave device includes a piezoelectric layer including first and second main surfaces, first and second electrode fingers on the first main surface and respectively connected to an input potential and an output potential, and a third electrode finger on at least one of the first and second main surfaces and connected to a reference potential. The first and second electrode fingers when seen from an electrode finger orthogonal direction orthogonal or substantially orthogonal to a direction in which the first and second electrode fingers extend. A region where the first and second electrode fingers overlap in the electrode finger orthogonal direction is a facing region. The third electrode finger overlaps with at least a portion of at least one facing region when seen from a main surface facing direction in which the first and second main surfaces face each other.