Low Profile MIMO Antenna Asymmetrical Radiators Null Reduction
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Solution Overview
Problem
Conventional MIMO antennas for in-building cellular networks are not ultra-low profile and omnidirectional, leading to significant nulls and limitations in azimuth plane radiation patterns, which affect their performance and aesthetic appeal for ceiling mounting.
Innovation Solution
The design of a low-profile, omnidirectional ceiling mount MIMO antenna with asymmetrical radiators and a slanted ground plane, featuring a printed circuit board configuration with radiators perpendicular to each other and a proximity coupling neutral line, which enhances radiation patterns and reduces passive intermodulation (PIM) while maintaining a compact size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional dipole antenna is used for MIMO applications, then the antenna can be mounted on the ceiling, but it produces very large nulls and is not omnidirectional in the azimuth plane
Solution Approach 1:
The patent employs asymmetrical radiators with different lengths (first radiator longer than second radiator) to eliminate the large nulls characteristic of conventional symmetrical dipole antennas. This asymmetry in the radiator structure creates omnidirectional radiation patterns in the azimuth plane, directly resolving the contradiction between reliable radiation performance and omnidirectional coverage.
Solution Approach 2:
The patent introduces a slanted ground plane that extends in both horizontal and vertical dimensions, creating a three-dimensional radiation structure. This dimensional extension allows the antenna to achieve omnidirectional coverage while maintaining low profile, resolving the contradiction between radiation pattern performance and directional limitations.
2Length of stationary object
If the antenna profile is reduced for aesthetic ceiling mounting, then the antenna becomes more compact, but radiation performance and omnidirectional patterns deteriorate
Solution Approach 1:
The patent achieves low profile by extending the ground plane structure in horizontal and vertical dimensions rather than increasing height. The slanted ground plane configuration allows the antenna to maintain a compact vertical profile while achieving omnidirectional radiation patterns through extended horizontal and vertical ground plane elements.
Solution Approach 2:
The patent integrates multiple functional elements (radiators, ground planes, feeding structures) into a compact nested arrangement where the asymmetrical radiators are positioned above the slanted ground plane structure. This nesting allows complex radiation functionality to be achieved within a reduced overall profile height.
3Device complexity
If symmetrical dipole configuration is used, then the antenna structure is simple, but it creates significant nulls and limits omnidirectional radiation
Solution Approach 1:
The patent modifies the simple symmetrical dipole structure by making the radiators asymmetrical (different lengths) and introducing a slanted ground plane. This controlled asymmetry eliminates the large nulls while maintaining structural simplicity, achieving omnidirectional radiation patterns without significantly increasing device complexity.
Data Source
AI summary
Disclosed are exemplary embodiments of antennas that may be configured to be low profile, omnidirectional, ceiling mountable, and/or multiple-input multiple-output (MIMO). In an exemplary embodiment, an antenna generally includes first and second radiators and a ground plane. First and second edge portions of the ground plane may configured to be operable for reducing null at azimuth plane to thereby allow the antenna to have more omnidirectional radiation patterns for the azimuth plane. The antenna may be configured to have an asymmetrical perpendicular dipole configuration. A neutral line may be spaced apart from and proximity coupled to the ground plane. The ground plane may comprise first and second ground plane extension arms and/or a slant cutout defined between spaced-apart first and second lower portions of the ground plane. The ground plane may include a bridge portion extending between the spaced-apart first and second lower portions of the ground plane.