Common Mode Filter With Adjustable Impedance Matching
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Solution Overview
Problem
Conventional common mode filters require redesign of slot structures and transmission wires when peripheral circuits change, leading to increased design time and potential impedance matching issues in limited spaces, resulting in poor performance.
Innovation Solution
A common mode filter with a slot structure on a circuit board and a filtering frequency adjusting device, comprising inductors and capacitors, allows dynamic adjustment of the passband by being placed across differential signal wires, enabling impedance matching without altering the overall circuit layout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the slot structure length and transmission wire length are used to control the center frequency, then the passband can be controlled, but the design time increases and impedance matching performance deteriorates when peripheral circuits change
Solution Approach 1:
The patent introduces a filtering frequency adjusting device with variable capacitors and/or inductors that can dynamically adjust the passband center frequency after the circuit board is manufactured. This transforms the static frequency control (fixed during design) into a dynamic control mechanism, allowing the same hardware to adapt to different peripheral circuits without redesigning the slot structure or transmission wires.
Solution Approach 2:
The patent changes the physical parameters (capacitance and/or inductance) of the filtering frequency adjusting device to control the passband characteristics. By varying these electrical parameters instead of changing the geometric dimensions of the slot structure, the system achieves frequency adjustment without requiring physical redesign or reconfiguration of the circuit board layout.
2Ease of manufacture
If the slot structure is formed to match the circuit board topography, then the layout can be optimized, but the impedance matching performance deteriorates in limited spaces
Solution Approach 1:
The patent extracts the frequency control function from the slot structure geometry and places it in a separate filtering frequency adjusting device. This separation allows the slot structure to maintain its simple, manufacturable form while the adjustable device handles the impedance matching and frequency control, eliminating the need for complex slot designs in limited spaces.
3Adaptability or versatility
If the layout of the slot structure and transmission wire is redesigned when peripheral circuits change, then the passband control can be maintained, but the design time increases
Solution Approach 1:
The filtering frequency adjusting device serves multiple functions: it controls the passband center frequency, maintains impedance matching, and adapts to different peripheral circuits. This single universal component replaces the need for redesigning the entire slot structure and transmission wire layout, significantly improving design efficiency while maintaining circuit compatibility.
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 solution improves signal transmission quality by reducing reflection phenomena and enhancing impedance matching, allowing for efficient adjustment of the passband without redesigning the circuit layout, thus optimizing common mode filter performance.
Implementation Method 1
the filtering frequency adjusting device includes at least one of at least one inductor and at least one capacitor
Implementation Method 2
the filtering frequency adjusting device includes at least one of at least one inductor and at least one capacitor
Data Source
AI summary
A common mode filter is disposed on a circuit board. A signal layer of the circuit board has a differential signal wire pair. The common mode filter has a slot structure and a filtering frequency adjusting device. The slot structure is formed on a reference voltage layer of the circuit board, wherein the slot structure surrounds the differential signal wire pair. The filtering frequency adjusting device is disposed on a corner part of the slot structure, wherein the filtering frequency adjusting device includes at least one of at least one capacitor and at least one inductor, and is disposed on the circuit board across the differential signal wire pair.