Common Mode Filter With Stacked Spiral Coils
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Solution Overview
Problem
Existing thin-film common mode filters for portable electronic devices face challenges in miniaturization due to complex structures, which affect volume and process variables, and require adjustments to conducting patterns to manage common mode impedance effectively.
Innovation Solution
A common mode filter design featuring a non-magnetic insulating substrate with stacked spiral coils and insulating layers, where the width and length of the coils satisfy specific relational expressions to achieve magnetic coupling and control the cutoff frequency, allowing for miniaturization while effectively eliminating common mode noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the conducting patterns of the multi-layer structure are modified to adjust common mode impedance, then the common mode impedance is controlled, but the structural complexity increases and volume increases
Solution Approach 1:
The patent controls common mode impedance by adjusting geometric parameters of the spiral coils (width W, length L, number of turns) rather than modifying conducting patterns. The relational expression [(14.1-fc)/6.5]2-[(fc)/4.5]2 provides a direct parameter relationship for impedance control, eliminating the need for complex pattern modifications while achieving precise impedance management.
Solution Approach 2:
Instead of modifying conducting patterns to control impedance, the patent inverts the approach by using a standardized multi-layer spiral coil structure where impedance control is achieved through geometric parameter optimization and magnetic layer integration, simplifying the overall structural design.
2Manufacturing precision
If the conducting patterns are modified to control common mode impedance, then the impedance is adjusted, but the volume of the electronic component increases
Solution Approach 1:
The patent achieves impedance control through parameter optimization of the spiral coil geometry (width W, length L, number of turns) and magnetic layer properties, allowing compact design. The relational expression provides direct guidance for parameter selection to achieve desired impedance in a minimized volume without pattern modifications.
Solution Approach 2:
The patent employs a nested multi-layer spiral coil structure where coils are stacked vertically with insulating layers between them. This nesting approach allows multiple functional layers to occupy a compact vertical space, controlling impedance while minimizing the horizontal footprint and overall component volume.
3Manufacturing precision
If a multi-layer structure with conducting patterns is used, then common mode impedance can be controlled, but the device complexity increases
Solution Approach 1:
The patent controls common mode impedance by optimizing geometric parameters (coil width W, length L, number of turns) and magnetic layer properties rather than modifying conducting patterns. This parameter-based approach simplifies the manufacturing process by eliminating complex pattern adjustments while maintaining precise impedance control through the relational expression.
Solution Approach 2:
Instead of using complex conducting pattern modifications to control impedance, the patent inverts the approach by employing a standardized multi-layer spiral coil structure where impedance control is achieved through geometric parameter optimization and magnetic layer integration, reducing process complexity.
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
The design achieves miniaturization and maintains a controlled range of cutoff frequencies, effectively managing common mode impedance and eliminating noise, thereby meeting the requirements of portable electronic devices.
Implementation Method 1
the first and second spiral coils can be magnetically coupled to be used in common to eliminate common mode noise
Data Source
AI summary
The common mode filter of the instant disclosure includes a non-magnetic insulating substrate, a stacked-layer structure, an insulating layer, and a magnetic layer. The stacked-layer structure is arranged on the non-magnetic insulating substrate. The magnetic layer is covered on the stacked-layer structure by the insulating layer arranged therebetween. The stacked-layer structure comprises a first coil and second coil, wherein the first coil is coupled to the second coil to suppress the common mode noise. Specially, a width W (mm) and a length L (mm) of at least one coil in the first and second coils satisfy the relational expression of:[(14.1−fc)/6.5]2<L/W<[(16.7−fc)/4.5]2 Where fc (MHz) is the cutoff frequency of a differential-mode signal.