Bent Branch-Line Coupler Layout for Compact PCB Power Splitting
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Solution Overview
Problem
Conventional 3 dB branch-line couplers occupy a large area on printed circuit boards, making them unsuitable for miniaturization in mobile and satellite communication devices.
Innovation Solution
A symmetrical branch-line coupler design utilizing bent branch lines and microstrip transmission lines, which reduces the coupler's size by 58.7% while maintaining performance, with specific structural dimensions and impedance configurations that ensure effective power splitting and isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional branch-line coupler design is used, then power splitting performance is maintained, but the area occupied on PCB is large
Solution Approach 1:
The patent applies curvature by designing bent branch lines instead of straight lines. The branch lines are configured with specific bend radii and angles to achieve the required electrical length and impedance transformation while occupying less physical space on the PCB, thereby reducing the overall coupler area while maintaining power splitting performance
Solution Approach 2:
The patent utilizes multi-layer PCB structure to arrange transmission lines in different physical layers. By transitioning from a single-plane layout to a three-dimensional multi-layer configuration, the coupler achieves compact size reduction while maintaining the required electrical characteristics and power splitting functionality
2Ease of operation
If conventional branch-line coupler design is used, then impedance matching is achieved, but the device size is large
Solution Approach 1:
The patent implements different impedance values for different sections of the transmission lines. Specifically, the branch lines have varying characteristic impedances (e.g., 70.7 ohms for main lines, 50 ohms for branch lines) to achieve proper impedance matching and power division. This localized impedance variation enables compact design while maintaining ease of operation
Solution Approach 2:
The patent changes physical parameters such as line width, spacing, and bend radius to achieve the desired impedance characteristics. By adjusting these geometric parameters, the coupler achieves proper impedance matching without requiring large dimensions, thus reducing the overall device area
Data Source
AI summary
A branch-line coupler, adapted to radio frequency circuits, includes an input port, a first output port, a second output port, an isolated port, a first transmission line, a second transmission line, a first bent branch line, and a second bent branch line. The first transmission line is electrically connected between the input port and the first output port, and carries two open branches. The second transmission line is electrically connected between the isolated port and the second output port, and carries two open branches. The first bent branch line is electrically connected between the input port and the isolated port. The second bent branch line is electrically connected between the first output port and the second output port. The open branches of the first transmission line and the second transmission line resemble the bone structure of a fish skeleton.