Folded Balun Structure With Ground Shielding for Compact RF Conversion
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Solution Overview
Problem
Existing baluns, such as flux coupled transformer and classical transformer baluns, are large in volume and not suitable for high-frequency applications, posing challenges for miniaturization in microwave communication devices.
Innovation Solution
A balun structure comprising a dielectric substrate with transmission lines and coupling structures, where branch lines are connected through grounding conductive layers and through holes, allowing for compact design and efficient signal conversion between balanced and unbalanced ports.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional transformer baluns are used, then signal conversion between balanced and unbalanced ports is achieved, but the device volume becomes large
Solution Approach 1:
The patent transitions from traditional planar or three-dimensional transformer structures to a folded transmission line configuration that utilizes vertical layering and horizontal folding to achieve compact integration. The transmission line is folded back on itself multiple times within a confined area, effectively using both two-dimensional and three-dimensional space to reduce the overall footprint while maintaining the required electrical length and signal conversion functionality.
Solution Approach 2:
The patent implements a nested structure where the transmission line is folded and layered upon itself, with multiple segments of the transmission line contained within a compact footprint. The ground conductive layers are positioned between signal transmission line segments, creating a nested arrangement where ground planes are embedded within the transmission line structure, effectively reducing the overall device volume while maintaining electromagnetic isolation.
2Ease of operation
If traditional transformer baluns are used, then signal conversion is achieved, but the device becomes heavy
Solution Approach 1:
The patent replaces traditional magnetic core-based transformer structures with a planar transmission line implementation using conductive layers on a substrate. This substitution eliminates the need for heavy magnetic materials and complex winding structures, achieving signal conversion through distributed capacitance and inductance of the transmission line geometry, thereby significantly reducing device weight while maintaining functionality.
Solution Approach 2:
The patent employs composite construction using conductive layers (copper or other conductive materials) deposited on a dielectric substrate, with ground conductive layers and signal transmission lines formed as separate planar patterns. This composite approach using thin-film deposition techniques replaces bulky traditional transformer components, achieving the required electromagnetic functionality with minimal material mass.
3Volume of moving object
If compact balun structures are designed, then device size is reduced, but electromagnetic shielding performance deteriorates
Solution Approach 1:
The patent introduces ground conductive layers as intermediary elements positioned between adjacent signal transmission line segments. These ground planes act as electromagnetic shields, blocking capacitive and inductive coupling between differential signal lines. The ground layers are connected to the reference ground, creating an intermediate shielding barrier that prevents electromagnetic interference while maintaining the compact folded structure.
Solution Approach 2:
The patent applies electromagnetic shielding selectively at critical locations where signal transmission lines are in close proximity or cross each other. Ground conductive layers are positioned specifically between adjacent signal segments that require isolation, rather than providing uniform shielding throughout the entire structure. This localized approach maintains compact dimensions while providing adequate electromagnetic isolation where most needed.
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 proposed balun structure achieves efficient signal conversion with reduced size, improved electromagnetic shielding, and low noise interference, suitable for high-frequency applications like radio-frequency signal transmission.
Implementation Method 1
one end of the first branch line close to the second coupling part is electrically connected with the first grounding conductive layer through a first through hole, and one end of the second branch line close to the first coupling part is electrically connected with the first grounding conductive layer through a second through hole; and in the same coupling structure, the first branch line of the first coupling part is in coupling connection with the second branch line of the second coupling part
Implementation Method 2
the first branch line of the first coupling part is in coupling connection with the second branch line of the second coupling part
Data Source
AI summary
A balun structure and an electronic device. The balun structure includes: a dielectric substrate; a first grounding conductive layer, a first transmission line, a second transmission line, and a third transmission line, wherein at least one coupling structure is connected in series between a first end and a second end of the third transmission line. The coupling structure includes a first coupling part and a second coupling part, wherein in the same coupling structure, one end of the first coupling part facing the second coupling part has at least one first branch line, and one end of the second coupling part facing the first coupling part has at least one second branch line; and in the same coupling structure, the first branch line of the first coupling part is in coupling connection with the second branch line of the second coupling part.