PCB Directional Coupler Ground Aperture for Higher Directivity
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Solution Overview
Problem
Directional couplers in wireless interface devices face challenges in achieving accurate signal sampling and efficient electromagnetic spectrum sharing, particularly at higher frequencies, due to size constraints and increased latency demands, which affect the performance of power amplifiers and overall transmitter efficiency.
Innovation Solution
A directional coupler design incorporating a meandered transmission line with a spatially paired ground structure featuring an aperture in a separate layer, which reduces the coupling factor and increases directivity, allowing for a compact form factor without significant insertion loss or additional cost, by using a printed circuit board (PCB) to etch the transmission lines and metal trace.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the coupled transmission line is meandered using multiple bends to reduce size, then the area occupied by the transmission line is reduced, but the coupling factor and isolation are degraded
Solution Approach 1:
A ground structure with an aperture is introduced as an intermediary element between the meandered transmission lines. The aperture in the ground structure compensates for the degradation caused by meandering, restoring the coupling factor and isolation performance while maintaining the compact size advantage of the meandered configuration.
Solution Approach 2:
The ground structure with aperture modifies the electromagnetic field distribution and impedance characteristics of the transmission lines. By changing the physical parameters of the ground structure (aperture size, position, shape), the coupling factor and isolation can be optimized to compensate for the meandering effects.
2Manufacturing precision
If the transmission lines are spaced apart to form a gap, then the coupling factor is reduced and isolation is increased, but the directivity needs to be enhanced
Solution Approach 1:
The ground structure with aperture serves as a mediator that enhances the directivity of the directional coupler. The aperture creates specific electromagnetic field patterns that improve the directional coupling characteristics, ensuring that the spacing between transmission lines effectively increases isolation while maintaining or enhancing directivity.
3Reliability
If a metal structure with aperture is added to improve directivity, then the coupling factor decreases and isolation increases, but the device complexity increases
Solution Approach 1:
The ground structure with aperture is merged with the existing PCB layout and transmission line structure. The aperture is integrated into the ground plane that is already part of the PCB design, combining multiple functions (ground reference, directivity enhancement, coupling control) into a single integrated structure rather than adding separate components.
Solution Approach 2:
The ground structure with aperture serves multiple functions simultaneously: it provides a ground reference for the transmission lines, enhances directivity through the aperture effect, and controls the coupling factor. This multi-functionality reduces the need for additional separate components, offsetting the complexity increase with functional consolidation.
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
This design enhances the directivity and isolation of the directional coupler, improving the accuracy of signal feedback and reducing power consumption, thereby supporting higher-frequency wireless standards like 5G and 6G while maintaining low costs and minimal insertion loss.
Implementation Method 1
a coupled transmission line that electromagnetically samples the signal propagating along the main transmission line
Implementation Method 2
The aperture in the metal structure can decrease the coupling factor and increase the isolation, which in turn can increase the directivity of the directional coupler
Data Source
AI summary
An apparatus is disclosed with a directional coupler and associated ground structure. In example aspects, the apparatus includes a printed circuit board. The printed circuit board includes a first layer and a second layer. The first layer includes a first transmission line and a second transmission line. The second transmission line includes at least one bend and is configured to electromagnetically couple to the first transmission line. The second transmission line is spaced apart from the first transmission line to form a gap in the first layer between the first transmission line and the second transmission line. The second layer includes a metal structure configured to provide a ground for the first transmission line. The metal structure includes an aperture positioned to at least partially overlap the gap in the first layer.