Balanced Filter Impedance Matching Common Mode Attenuation
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Solution Overview
Problem
Existing balanced filters fail to adequately attenuate common mode signals in the pass band due to mismatched impedance between terminals and the presence of a DC feed terminal, leading to suboptimal input/output characteristics.
Innovation Solution
A balanced filter design incorporating an unbalanced terminal, unbalanced-side inductor, balanced-side inductor, power supply line, and matching network, where the unbalanced-side inductor is connected to ground, the balanced-side inductor couples electromagnetically with the unbalanced-side inductor, and the matching network adjusts impedance between the balanced terminals to match the power supply line's impedance, effectively attenuating common mode signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a DC feed terminal is provided in the balanced-side inductor, then power supply is enabled, but impedance mismatch occurs between terminals causing common mode signal attenuation failure
Solution Approach 1:
The balanced-side inductor is divided into multiple sections with different inductance values on either side of the DC feed terminal connection point. This segmentation allows independent optimization of impedance characteristics for each section, enabling both power supply functionality and common mode signal attenuation to coexist without compromise.
2Device complexity
If inductance values are made equal on both sides of DC feed terminal, then structure is simplified, but impedance matching cannot be achieved for common mode signal attenuation
Solution Approach 1:
Different inductance values are assigned to different sections of the balanced-side inductor based on their specific functional requirements. The section closer to one terminal has a different inductance than the section closer to the other terminal, optimizing impedance characteristics locally at each terminal while maintaining overall system functionality.
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 solution enables significant attenuation of common mode signals in the pass band, ensuring desired input/output characteristics by matching impedances and enhancing bandpass characteristics through electromagnetic field coupling.
Implementation Method 1
The balanced-side inductor is provided between the first balanced terminal and the second balanced terminal and couples to the unbalanced-side inductor via an electromagnetic field
Data Source
AI summary
A balanced filter includes an unbalanced terminal, an unbalanced-side inductor, a first balanced terminal, a second balanced terminal, a balanced-side inductor, a power supply line, and a matching network. The unbalanced-side inductor is provided between the unbalanced terminal and a ground. The balanced-side inductor is provided between the first balanced terminal and the second balanced terminal and couples to the unbalanced-side inductor via an electromagnetic field. The power supply line includes a first end connected to a middle portion of the balanced-side inductor and a second end connected to a direct-current power supply. The matching network matches a first impedance between the first balanced terminal and the second end of the power supply line to a second impedance between the second balanced terminal and the second end of the power supply line.