MIMO Antenna Isolation via Segmented Ground Stubs
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Solution Overview
Problem
Multiple antennas in close proximity interfere with each other, degrading their performance in devices like Wi-Fi routers.
Innovation Solution
A multiple-input multiple-output (MIMO) antenna design featuring a printed circuit board with a ground layer, slots, and ground stubs, along with antenna elements and coupling elements, is used to maintain isolation between antennas, enhancing RF isolation and bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If multiple antennas are mounted in close proximity to improve device integration, then device compactness is improved, but antenna performance degrades due to mutual interference
Solution Approach 1:
The ground layer is segmented into multiple isolation regions, with each region associated with a specific antenna element. These isolation regions are electrically connected to the ground and physically separate the antennas from each other, allowing compact antenna placement while maintaining performance through electrical isolation between adjacent antenna elements
Solution Approach 2:
Isolation regions serve as intermediary structures between adjacent antenna elements. These ground-connected regions act as electromagnetic shields that mediate the interaction between antennas, blocking harmful mutual interference while allowing the antennas to be positioned in close proximity for compact device design
2Area of stationary object
If antenna elements are placed close together to reduce device footprint, then area utilization is improved, but isolation between antennas deteriorates
Solution Approach 1:
The ground layer is divided into multiple isolation regions, each corresponding to a specific antenna element. This segmentation creates distinct electrical zones that prevent electromagnetic coupling between adjacent antennas, enabling dense area utilization while maintaining greater than -30 dB isolation between antenna elements
Solution Approach 2:
Different regions of the ground layer are assigned different functions: some regions serve as isolation regions electrically connected to ground for shielding, while other regions serve as feed network transmission lines. This local differentiation allows the ground layer to simultaneously provide isolation and signal routing functions, enabling compact antenna placement with adequate isolation
3Reliability
If isolation structures are added between antennas to reduce interference, then antenna isolation is improved, but device complexity increases
Solution Approach 1:
The ground layer serves multiple functions simultaneously: it provides the reference plane for antenna operation, contains isolation regions for electromagnetic shielding, and incorporates feed network transmission lines for signal routing. This multi-functionality eliminates the need for separate isolation structures, achieving greater than -30 dB isolation without increasing overall device complexity
Solution Approach 2:
The isolation regions and feed network are merged into a single integrated ground layer structure. The isolation regions are electrically connected to ground and form part of the same planar structure as the transmission lines, combining shielding and signal routing functions into one layer rather than requiring separate isolation components
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 design allows for close antenna spacing while maintaining greater than -30 dB isolation and covering the entire 5 GHz band, reducing interference and improving data throughput.
Implementation Method 1
a plurality of slots comprising dielectric material in a plane of the ground layer, each of the plurality of slots extending a predetermined electrical length from an edge of the printed circuit board, and at least one ground stub, the at least one ground stub comprising an extension of the ground layer of a predetermined electrical length at a predetermined angle relative to the edge of the printed circuit board
Data Source
AI summary
A multiple input multiple output (MIMO) antenna is provided. The MIMO antenna may include, but is not limited to, a printed circuit board having a plurality of edges and a ground layer including, but not limited to a plurality of antenna element mounting locations, at least one of the plurality of antenna element mounting locations being arranged on a first side of the printed circuit board and at least one of the plurality of antenna element mounting locations being arranged on a second side of the printed circuit board, a plurality of slots, each of the plurality of slots extending a predetermined distance from an edge of the printed circuit board, and at least one ground stub, the at least one ground stub comprising an extension of the ground layer of a predetermined electrical length at a predetermined angle relative to the edge of the printed circuit board.