Balun with Intermediate Non-Terminated Conductor for Impedance Matching
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Solution Overview
Problem
High power broadband communication systems require impedance matching and signal balancing, which is challenging due to undesired coupling in unbalanced circuits, especially at microwave frequencies where achieving perfect balance is difficult.
Innovation Solution
A balun design featuring first and second transmission lines with a shared conductor, where the second conductor is inductively coupled and open-circuited at both ends, surrounded by a ferrite sleeve, allowing for impedance transformation and signal balancing over a wide bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an unbalanced circuit with ground plane return is used, then circuit wiring is simplified, but undesired coupling occurs between signals
Solution Approach 1:
The patent introduces a balun device as an intermediary component between the unbalanced transmitter and the balanced antenna. The balun contains a transformer with primary and secondary windings that mediates the signal transition, converting the unbalanced signal from the transmitter into a balanced signal for the antenna, thereby eliminating direct coupling paths through the ground plane while maintaining wiring simplicity.
2Object-affected harmful factors
If a balanced circuit with two separate return paths is used, then signal coupling is reduced, but achieving perfect balance is difficult at microwave frequencies
Solution Approach 1:
The patent merges the two separate balanced return paths into a single shared ground connection at the transmitter side through the transformer structure. The transformer windings are positioned and coupled such that they create equal and opposite currents that naturally cancel each other's magnetic fields, achieving balance without requiring two completely separate return paths, thus simplifying the structure while maintaining balance accuracy.
Solution Approach 2:
The patent replaces the mechanical/physical requirement for perfect symmetry in balanced circuit layout with an electromagnetic solution using transformer coupling. The magnetic coupling between windings and the resulting induced voltages provide the balancing action, substituting electromagnetic field control for precise mechanical symmetry, which is particularly valuable at microwave frequencies where physical tolerances are difficult to maintain.
3Adaptability or versatility
If coaxial baluns are used for broadband applications, then impedance transformation is achieved, but device complexity increases
Solution Approach 1:
The patent designs a transformer-based balun that performs multiple functions within a single device: impedance transformation between different impedance levels (e.g., 50 ohms to 200 ohms), balanced-to-unbalanced conversion, and broadband signal transmission. The transformer structure with appropriately chosen winding ratios and coupling coefficients achieves all these functions simultaneously, eliminating the need for separate components for each function and reducing overall device 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 balun effectively transforms impedance and minimizes coupling, maintaining signal balance and reducing noise, thereby enhancing the performance of high power broadband communication systems.
Implementation Method 1
a ferrite sleeve may surround the second conductor
Implementation Method 2
The second conductor may have first and second ends. The first end of the second conductor may be proximate to the first end of the first conductor. The first and second ends of the second conductor also may both be open-circuited (unconnected to the first conductor and/or unconnected to the circuit ground).
Data Source
AI summary
A balun comprising first and second transmission lines having a shared intermediate conductor. The first transmission line may include first and second conductors. The first conductor may have a first end for conducting an unbalanced signal relative to a circuit ground and a second end for conducting a balanced signal. The second conductor may have first and second ends proximate the respective first and second ends of the first conductor. The first and second ends of the second conductor may be open-circuited. The second transmission line may include the second conductor and a third conductor having a first end connected to circuit ground and a second end for conducting the balanced signal. The second conductor may surround the first and third conductors, and one or more ferrite sleeves may surround the second conductor.