LC Resonant Balun Circuit for Interference Wave Rejection
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Solution Overview
Problem
There is a need for a balanced-unbalanced transformer circuit that effectively reduces interference waves in amplifier circuits, as existing solutions are inadequate in this regard.
Innovation Solution
A balanced-unbalanced transformer circuit is designed, comprising a main line and a sub-line connected such that their directions are identical, with an unbalanced node for input and output of unbalanced signals and balanced nodes for balanced signals, and includes an LC resonant circuit connected between the ends and reference potential, allowing for impedance conversion and interference wave reduction using passive elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional choke balun is used for balanced-unbalanced transformation, then the circuit structure is simple, but interference waves cannot be sufficiently removed
Solution Approach 1:
The transmission line is segmented into a main line and a sub-line with identical directional coupling. This segmentation creates separate paths for differential mode signals while providing common mode rejection, enabling sufficient interference wave removal without overly complicating the circuit structure.
Solution Approach 2:
An LC resonant circuit is introduced as an intermediary element connected between one end of the main line and the reference potential. This resonant circuit acts as a frequency-selective mediator that enhances interference wave rejection at specific frequencies while maintaining the overall circuit structure in a manageable form.
2Object-affected harmful factors
If passive elements only are used for interference wave removal, then cost is reduced, but the ability to selectively remove interference waves may be limited
Solution Approach 1:
The LC resonant circuit utilizes parameter changes at specific frequencies to achieve frequency-selective interference wave removal. By tuning the resonant frequency of the LC circuit, the system can adaptively reject interference waves at different frequencies while maintaining cost-effectiveness through the use of passive elements only.
3Productivity
If the main line and sub-line are coupled with identical directions, then the transformation efficiency is improved, but the circuit configuration becomes more constrained
Solution Approach 1:
While the main line and sub-line are coupled with identical directions to improve transformation efficiency, the circuit introduces asymmetry through the LC resonant circuit connection at one specific end. This controlled asymmetry allows the system to maintain high transformation efficiency while providing the necessary constraints for frequency-selective interference rejection.
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 circuit efficiently transforms unbalanced signals into balanced signals and vice versa, effectively removing interference waves while reducing costs by utilizing only passive elements, and exhibits frequency selectivity to differentiate between input signals and interference waves.
Implementation Method 1
a first LC resonant circuit connected between the second end and the reference potential or between the third end and the reference potential
Data Source
AI summary
A main line (transmission line) having a first end and a second end. A sub-line (transmission line) coupled to the main line. An unbalanced signal is input to and output from an unbalanced node connected to the first end. A balanced signal is input to and output from a first balanced node and a second balanced node. The main line and the sub-line are coupled to each other. A direction of the main line is identical to a direction of the sub-line. The second end and the third end are connected to a reference potential. The first balanced node and the second balanced node are connected to the unbalanced node and the fourth end, respectively. A first LC resonant circuit is connected between the second end and the reference potential or the third end and the reference potential.