Ladder-Type SAW Filter Layout Without Dielectric Bridge Overlap
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Solution Overview
Problem
Longitudinally coupled resonator type surface acoustic wave filters face challenges in miniaturization due to the presence of a dielectric bridge, which increases chip size and introduces parasitic capacitance, affecting performance.
Innovation Solution
Eliminate the need for a dielectric bridge by ensuring the ground line does not overlap with the signal line, using electrode fingers for grounding, and reducing the number of dielectric bridges to simplify the manufacturing process and enhance stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dielectric bridge is introduced in the longitudinally coupled resonator type surface acoustic wave filter, then the filter structure is established and signal transmission is enabled, but the chip area increases and parasitic capacitance is introduced
Solution Approach 1:
The patent removes the dielectric bridge from the filter structure entirely. By redesigning the ground line routing to avoid overlapping with signal lines, the dielectric bridge component is extracted and eliminated, thereby reducing chip area while maintaining structural stability through alternative grounding paths.
Solution Approach 2:
The patent resolves the spatial conflict between signal lines and ground lines by transitioning from a planar overlapping arrangement to a non-overlapping spatial configuration. The ground line is routed in a different spatial path that avoids intersection with signal lines, eliminating the need for vertical separation via dielectric bridge.
2Reliability
If a dielectric bridge is introduced in the longitudinally coupled resonator type surface acoustic wave filter, then the filter structure is established, but parasitic capacitance increases and filter performance deteriorates
Solution Approach 1:
The dielectric bridge, which is the source of parasitic capacitance, is completely removed from the structure. The filtering function is maintained through the resonator configuration and alternative grounding method, extracting the harmful capacitance effect while preserving the essential filter operation.
Solution Approach 2:
The patent converts the potential harm of close signal-ground line proximity into a benefit by deliberately routing the ground line to avoid overlap. This design choice transforms what could have been a parasitic capacitance problem into an opportunity for optimized signal integrity and reduced unwanted electrical coupling.
3Reliability
If a dielectric bridge is used for grounding in the longitudinally coupled resonator type surface acoustic wave filter, then electrical connection is established, but the manufacturing process becomes more complex
Solution Approach 1:
The dielectric bridge component and its associated manufacturing steps are removed from the process. The electrical grounding connection is achieved through simplified metal layer routing that does not require additional dielectric structures, reducing manufacturing complexity while maintaining connection stability.
Solution Approach 2:
The grounding function is merged into the existing metal interconnect structure rather than being implemented as a separate dielectric bridge component. The ground line is integrated into the standard metallization layers, combining multiple functions into fewer process steps and simplifying manufacturing.
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 reduces parasitic capacitance, enabling miniaturization and improving performance without degrading filter characteristics such as insertion loss and out-of-band attenuation.
Implementation Method 1
longitudinally coupled resonator type surface acoustic wave filter
Implementation Method 2
interdigital transducer includes electrode fingers alternately connected to first potential and second potential
Implementation Method 3
longitudinally coupled resonator type
Implementation Method 4
elastic wave filter
Data Source
AI summary
The present disclosure discloses a longitudinally coupled resonator type surface acoustic wave filter and an elastic wave filter. The longitudinally coupled resonator type surface acoustic wave filter includes: a signal terminal, a ground terminal, and an interdigital transducer group. The interdigital transducer group includes at least a first interdigital transducer and a second interdigital transducer arranged along a first direction. The first interdigital transducer includes a first busbar, and the second interdigital transducer includes a second busbar. The first busbar is electrically connected to the signal terminal via a signal line, and the second busbar is electrically connected to the ground terminal via a first ground line. The first ground line does not overlap with the signal line.