Segmented Acoustic Wave Filter for Spurious Emission Suppression
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Solution Overview
Problem
Existing acoustic wave filters face challenges in reducing spurious emissions outside the pass band while maintaining low loss within the pass band, primarily through adjustments to the electrode finger structure of segmented resonators.
Innovation Solution
The acoustic wave filter design includes segmented resonator groups with specific capacitance and withdrawal ratio configurations for IDT electrodes, where C1/r1 > C2/r2 and r1 < r2, and a product of electrode parameters for one IDT electrode is larger than that of another, to reduce spurious emissions while ensuring low loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the electrode finger structure of the withdrawal electrode in segmented resonators is adjusted, then the steepness in the vicinity of the pass band is improved, but the spurious emissions outside the pass band cannot be sufficiently reduced
Solution Approach 1:
The resonator is divided into multiple segments (first resonator and second resonator) with different electrode finger structures. Each segment has distinct capacitance values (C1, C2) and withdrawal ratios (r1, r2), allowing independent optimization of different frequency regions. This segmentation enables the first resonator to control pass band characteristics while the second resonator suppresses spurious emissions.
Solution Approach 2:
Different parts of the resonator (first resonator vs. second resonator) are given different local properties through varying electrode configurations. The first resonator has electrode parameters optimized for pass band steepness, while the second resonator has parameters specifically tuned to reduce spurious emissions, creating localized functional zones within the overall resonator structure.
2Manufacturing precision
If only the electrode finger structure of the withdrawal electrode is adjusted, then the steepness is improved, but low loss within the pass band cannot be simultaneously secured while reducing spurious emissions
Solution Approach 1:
The resonator is divided into multiple segments (first resonator and second resonator) with different electrode finger structures. Each segment has distinct capacitance values (C1, C2) and withdrawal ratios (r1, r2), allowing independent optimization of different frequency regions. This segmentation enables the first resonator to control pass band characteristics while the second resonator suppresses spurious emissions.
Solution Approach 2:
Different parts of the resonator (first resonator vs. second resonator) are given different local properties through varying electrode configurations. The first resonator has electrode parameters optimized for pass band steepness, while the second resonator has parameters specifically tuned to reduce spurious emissions, creating localized functional zones within the overall resonator structure.
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 design effectively reduces spurious emissions outside the pass band while maintaining low loss within the pass band, enhancing the filter's performance.
Implementation Method 1
an acoustic wave resonator including an IDT electrode on a substrate having piezoelectricity
Data Source
AI summary
An acoustic wave filter includes at least one of a first series arm resonator circuit in a path connecting input/output terminals and a first parallel arm resonator circuit between a node in the path and ground. At least one of the first series arm resonator circuit and the first parallel arm resonator circuit includes a segmented resonator group including first and second acoustic wave resonators connected in series, an IDT electrode included in the first acoustic wave resonator includes a first withdrawal electrode, and C1/r1>C2/r2 and r1<r2 are satisfied.