Longitudinally Coupled Resonator Filter Layout for Transverse Ripple Reduction
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Solution Overview
Problem
Existing longitudinally coupled resonator acoustic wave filters with narrow-pitch electrode finger portions face challenges in reducing ripples caused by transverse modes, leading to decreased electric power handling capability and weather resistance due to the presence of wide portions in these areas.
Innovation Solution
The design includes a configuration where no wide portions are present in the narrow-pitch electrode finger portions, with wider portions only in the remaining electrode finger portions, effectively reducing ripples and maintaining high electric power handling and weather resistance by maintaining a sufficient pitch and avoiding mass-adding layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If wide portions are disposed in a narrow-pitch electrode finger portion to reduce ripples, then ripple reduction is improved, but the spacing between wide portion and adjacent electrode finger becomes narrow, decreasing electric power handling capability
Solution Approach 1:
The patent applies local quality by providing wide portions only in specific regions (first and second regions) of the electrode fingers, while omitting them in the narrow-pitch electrode finger portion. This localized differentiation allows ripple reduction in areas where it is needed without compromising the spacing and power handling capability in the narrow-pitch region.
2Object-generated harmful factors
If mass-adding layer is disposed to form edge area instead of wide portion, then ripple reduction is achieved, but the gap aspect ratio increases, causing film quality deterioration and degraded weather resistance
Solution Approach 1:
The patent uses local quality by selectively forming wide portions only in the first and second regions of the electrode fingers, while deliberately omitting them in the narrow-pitch electrode finger portion. This spatial differentiation achieves ripple reduction where needed without increasing gap aspect ratio in the narrow-pitch region, thereby avoiding film quality deterioration and maintaining weather resistance.
3Ease of manufacture
If a structure with fixed length and width of electrode areas is used, then manufacturing is simplified, but it is effective only for single propagation velocity and ineffective where propagation velocity changes, failing to sufficiently reduce ripples
Solution Approach 1:
The patent implements local quality by differentiating the electrode finger structure into multiple regions: some regions have wide portions for ripple reduction, while the narrow-pitch region omits wide portions to maintain proper spacing. This localized structural differentiation allows the device to handle varying propagation velocities effectively while maintaining manufacturing feasibility through a systematic regional design approach.
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 effectively prevents or reduces ripples caused by transverse modes, enhances electric power handling capability, and maintains robust weather resistance without deteriorating film quality.
Implementation Method 1
a piezoelectric substrate
Data Source
AI summary
A longitudinally coupled resonator acoustic wave filter includes first, second, and third IDT electrodes disposed on a piezoelectric substrate. The first, second, and third IDT electrodes include first electrode fingers and second electrode fingers. The first, second, and third IDT electrodes include narrow-pitch electrode finger portions in which the pitch between electrode fingers is narrower than in the remaining electrode finger portions. In the first, second, and third IDT electrodes, an overlap area includes a central area and first and second edge areas at opposite ends of the central area in the direction in which the first and second electrode fingers extend. In the remaining electrode finger portions the first electrode fingers and the second electrode fingers include wide portions in the first or second edge area.