Inverted Balun With DC Isolated Differential Ports
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Solution Overview
Problem
Existing balun implementations, such as Marchand and Merrill baluns, are limited in supporting wideband applications and require excessive line-widths, with direct current paths between balanced ports and ground, necessitating the use of decoupling capacitors that increase size and complexity.
Innovation Solution
A balun design featuring a first and second coupler structure connected to provide DC isolation between balanced ports without decoupling components, utilizing a resistive element to isolate the balanced ports from ground potential, and employing a vertical interdigital coupler configuration with transmission line layers to achieve improved coupling and reduced size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional balun implementations (Marchand or Merrill baluns) are used, then DC paths between balanced ports and ground are provided, but decoupling capacitors are required which increase device size and complexity
Solution Approach 1:
The patent extracts and removes the decoupling capacitors from the balun structure by redesigning the coupling mechanism. The coupled transmission lines are configured to provide inherent DC isolation between balanced ports through their physical arrangement and grounding scheme, eliminating the need for separate decoupling components and thereby reducing device complexity while maintaining DC isolation reliability
Solution Approach 2:
The patent merges the DC isolation function with the signal coupling function by integrating the grounding scheme directly into the coupled transmission line structure. The balanced ports are grounded through the transmission line configuration itself rather than through separate decoupling capacitors, combining multiple functions into a unified structure that reduces overall device complexity
2Reliability
If traditional balun implementations are used, then signal coupling is achieved, but excessive line-widths are required which increase device area
Solution Approach 1:
The patent transitions from planar transmission line configurations to a three-dimensional stacked configuration where coupled transmission lines are positioned on different layers. This vertical arrangement allows for tighter coupling with reduced line widths compared to planar designs, as the coupling occurs through the vertical dimension rather than requiring extensive horizontal spacing, thereby reducing the overall device area while maintaining effective signal coupling
Solution Approach 2:
The patent employs a nested configuration where transmission lines are arranged in stacked layers with alternating ground planes. The inner transmission lines are positioned between outer transmission lines and ground planes, creating a nested structure that maximizes coupling efficiency within a compact footprint. This nested arrangement allows for reduced line widths while maintaining the necessary coupling between balanced and unbalanced ports
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 a compact balun design with enhanced coupling characteristics, reduced size, and improved performance by eliminating the need for decoupling capacitors, while maintaining effective DC isolation and supporting wider bandwidths.
Implementation Method 1
A balun may be implemented by disposing two conductors in relative proximity to each other such that an RF signal propagating along a main conductor is coupled to a secondary conductor. An electromagnetic field is coupled to the secondary conductor
Data Source
AI summary
The present invention is directed to a balun that includes a first coupler structure having a first port of a balanced port pair and an unbalanced port. A second coupler structure includes a second port of the balanced port pair. The second coupler port structure being connected to the first coupler structure such that the second port of the balanced port pair is DC isolated from the first port of the balanced port pair without decoupling components.