Miniaturized Branch-Line Coupler Using Bent Transmission Lines
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Solution Overview
Problem
Conventional branch-line couplers occupy a large area on printed circuit boards, making them unsuitable for miniaturized microwave communication devices despite their widespread use in microwave integrated circuits.
Innovation Solution
A minimized branch-line coupler design utilizing bent transmission lines and long strip transmission lines, which reduces the overall size by 56% while maintaining high performance, is introduced. This design includes a symmetrical configuration with bent transmission lines connected between ports and long strip transmission lines linking specific ports, optimizing the layout for smaller PCB space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional quarter-wavelength lines are used to construct a branch-line coupler, then the coupler achieves proper power splitting and isolation, but it occupies a large area on the printed circuit board
Solution Approach 1:
The patent applies curvature to the transmission lines by using bent transmission lines instead of straight quarter-wavelength lines. The bent configuration allows the transmission lines to achieve the required electrical length and impedance transformation while occupying less physical space on the PCB, thus resolving the contradiction between maintaining proper power splitting performance and reducing PCB area.
Solution Approach 2:
The patent transitions from a planar layout to a three-dimensional configuration by stacking multiple transmission line layers. The bent transmission lines are arranged across different layers with optimized spacing, allowing the coupler to achieve the required electrical characteristics in a compact vertical footprint, thereby reducing the horizontal PCB area while maintaining reliability.
2Area of stationary object
If the branch-line coupler size is reduced for miniaturization, then it becomes suitable for mobile communication devices, but the isolation and performance may deteriorate
Solution Approach 1:
The bent transmission lines provide precise control over the electrical path length and coupling characteristics. By optimizing the bend radius and configuration, the patent maintains the required isolation between ports while achieving a compact size suitable for mobile communication devices, thus preventing performance deterioration during miniaturization.
Solution Approach 2:
The patent optimizes key parameters including the bending angle, bend radius, line width, and spacing between transmission lines. These parameter adjustments allow the coupler to maintain proper isolation and power splitting performance while achieving significant size reduction for miniaturized applications.
Data Source
AI summary
A branch-line coupler suitable for use in mobile devices includes a first, second, third, and fourth ports, respectively acting as input, transmitted, coupled, and isolated port. A first, second, third, and fourth connection parts are connected to the ports and transmission lines. First and second bent transmission lines are electrically connected between first and second ports. Third and fourth bent transmission lines are electrically connected between third and fourth ports. A first long strip transmission line is electrically connected between the first port and the fourth port. A second long strip transmission line is electrically connected between the second port and the third port. The branch-line coupler occupies a small area and has high performance.