RF Filter Ground Electrode Segmentation to Limit Magnetic Coupling
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Solution Overview
Problem
Filter devices with multiple LC resonant circuits connected to a common ground electrode experience unintended magnetic coupling, leading to degradation of filter characteristics due to electric current flow through the ground electrode, which complicates achieving desired filter performance.
Innovation Solution
The filter device separates the ground electrodes connected to different resonant circuits, preventing electric current flow between them and thereby reducing unintended magnetic coupling, while maintaining a compact size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a common ground electrode is used to connect multiple resonant circuits, then the ground potential is stabilized and variation among resonant circuits is reduced, but electric current flows between resonant circuits via the ground electrode causing unintended magnetic coupling and degradation of filter characteristics
Solution Approach 1:
The common ground electrode is divided into multiple separate ground electrodes, each connected to specific resonant circuits. This segmentation prevents electric current from flowing between resonant circuits through the ground electrode, thereby eliminating unintended magnetic coupling while maintaining stable ground potential for each resonant circuit group.
2Object-generated harmful factors
If separate ground electrodes are used for different resonant circuits, then unintended magnetic coupling is prevented, but the device complexity increases due to additional ground electrode structures
Solution Approach 1:
The harmful function of the ground electrode (providing a current path between resonant circuits) is extracted and eliminated by separating the ground electrodes. Each resonant circuit or group of resonant circuits is connected to its own dedicated ground electrode, removing the unwanted current path while maintaining necessary grounding functions.
3Volume of moving object
If the filter device size is reduced by optimizing via placement, then integration is improved, but the design flexibility is constrained by limited placement options
Solution Approach 1:
The ground electrodes are arranged in different layers of the multilayer substrate, utilizing the vertical dimension to achieve separation between ground electrodes connected to different resonant circuits. This three-dimensional arrangement reduces the planar footprint of the device while maintaining adequate separation to prevent magnetic coupling, thereby reducing overall device size without constraining design flexibility.
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 maintains desired filter characteristics by setting attenuation poles at designed frequencies, improves design flexibility, and reduces the size of the filter device by optimizing via placement.
Implementation Method 1
an electric current may flow between the resonant circuits via the ground electrode, and as a result, strong magnetic coupling may occur between the resonant circuits
Data Source
AI summary
A filter device includes a dielectric substrate, first and second terminals on an outer surface of the dielectric substrate, first and second resonant circuits, and first and second ground electrodes. The first resonant circuit is connected to the first terminal. The second resonant circuit is connected to the second terminal. The first ground electrode is connected to the first resonant circuit. The second ground electrode is connected to the second resonant circuit and is separated from the first ground electrode.