Common Mode Noise Filter With Stacked Coils
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Solution Overview
Problem
Conventional common mode noise filters with three coils suffer from poor magnetic coupling due to large distances between coils, leading to high residual inductance and degradation of differential signals in high-speed transmission systems like MIPI C-PHY.
Innovation Solution
The design includes three independent coils with specific overlapping configurations on insulator layers, ensuring balanced magnetic coupling by adjusting the positions and connections of coil conductors to minimize stray capacitance and enhance magnetic flux cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If three coils are disposed in a stacking direction with large distances between them, then the device structure is simple and easy to manufacture, but magnetic coupling between coils is poor leading to high residual inductance and degradation of differential signals
Solution Approach 1:
The patent transitions from a conventional planar coil arrangement to a three-dimensional stacked configuration where coils are disposed on different insulator layers in the stacking direction. This dimensional change allows coils to be positioned closer together vertically, enhancing magnetic coupling while maintaining manufacturing simplicity through standardized layer stacking.
Solution Approach 2:
The patent implements a nested structure where coil conductors are arranged to overlap each other when viewed from above, with at least a part of the second coil overlapping the third coil. This nesting arrangement maximizes magnetic coupling between adjacent coils while minimizing the horizontal footprint, thereby reducing residual inductance without complicating the manufacturing process.
2Reliability
If coil conductors are positioned to achieve balanced magnetic coupling, then differential signal quality is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies local quality by making the coil conductors have different configurations in different regions. Specifically, the first coil conductor overlaps the second coil, and the second coil conductor overlaps the third coil, creating localized overlapping regions that enhance magnetic coupling where needed while maintaining simpler structures in other areas.
Solution Approach 2:
The patent segments the coil structure into three independent coils disposed on separate insulator layers, each with its own conductor path. This segmentation allows independent optimization of each coil's configuration to achieve balanced magnetic coupling, while the modular layer structure keeps the overall device complexity manageable through systematic assembly.
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 signal quality with reduced loss in differential signals by achieving balanced magnetic coupling and low impedance for differential signals, effectively suppressing common mode noise in high-speed transmission systems.
Implementation Method 1
when common mode noise is input, magnetic fields generated at coils 2 to 4 enhance each other, and coils 2 to 4 operate as inductors to suppress noise
Implementation Method 2
This common mode noise filter provides balanced magnetic coupling of the three coils and thus does not deteriorate differential signals
Data Source
AI summary
A common mode noise filter includes first to fourth insulator layers stacked in a stacking direction and first to third coils provided on the first to fourth insulator layers independently of one another. The first coil includes a first coil conductor provided on the first insulator layer and a second coil conductor provided on the fourth insulator layer and connected to the first coil conductor. The second coil is provided on the second insulator layer. The third coil is provided on the third insulator layer. The first coil conductor overlaps the second coil viewing from above. At least a part of the second coil overlaps at least a part of the third coil viewing from above. The second coil conductor overlaps the third coil viewing from above.