Omnidirectional PCB Antenna with Amplitude Taper for Skyward Suppression
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Solution Overview
Problem
Conventional antennas fail to adequately suppress radiation in ≥30° skyward regions to at most −15 dB below the peak gain, are not omnidirectional in the azimuth plane, and lack sufficient operational bandwidth, failing to meet FCC EIRP requirements for U-NII bands.
Innovation Solution
A vertically-polarized omnidirectional antenna with broadband amplitude taper, featuring a design with a host PCB, metal flooded ground plane, and amplitude tapers on antenna PCBs, utilizing transmission lines with varying impedances to form dipole pairs, and a Marchand balun for balanced radiation patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional antenna designs are used, then the antenna structure is simple, but the radiation in ≥30° skyward regions cannot be suppressed to at most −15 dB below peak gain
Solution Approach 1:
The antenna is divided into multiple dipole pairs arranged in a specific geometry, with each dipole pair contributing to the overall radiation pattern. The segmentation of the antenna into discrete radiating elements allows for controlled interference patterns that suppress skyward radiation while maintaining horizontal omnidirectional coverage.
Solution Approach 2:
Different regions of the antenna are designed with different characteristics - the dipole pairs are positioned and oriented to create specific radiation patterns in different directions. The local arrangement of dipoles creates constructive interference in the horizontal plane and destructive interference in the skyward regions, achieving directional control through spatial distribution.
2Ease of operation
If conventional antenna designs are used, then the manufacturing process is simple, but the antenna is not omnidirectional in the azimuth plane
Solution Approach 1:
The antenna employs a specific asymmetric arrangement of dipole pairs where the spacing, orientation, and feeding of each dipole pair is deliberately different from others. This asymmetric configuration creates the desired omnidirectional pattern in the azimuth plane while allowing control over the elevation plane radiation through the vertical arrangement of elements.
Solution Approach 2:
Multiple dipole pairs are combined in a unified antenna structure with shared feeding networks and common ground plane. The merging of multiple radiating elements with different orientations and positions creates the omnidirectional radiation pattern through constructive interference in all azimuth directions while maintaining the ability to suppress skyward radiation.
3Adaptability or versatility
If conventional antenna designs are used, then the design is straightforward, but the operational bandwidth is insufficient
Solution Approach 1:
The antenna incorporates dynamic impedance matching through transmission lines with varying characteristic impedances connecting the dipole pairs to the feed network. The impedance transformation ratio varies with frequency, allowing the antenna to maintain good matching across a broad frequency range. The dynamic nature of the impedance transformation enables wideband operation while managing the complexity of the feeding network.
Data Source
AI summary
A vertically-polarized omnidirectional antenna, including: a body including: a host printed circuit board (PCB) including: first and second slots, and a metal flooded ground plane, first and second antenna PCBs forming four dipole pairs, the first and second antenna PCBs mounted to the host PCB, respective first to third ground connection fillet tabs, the first and second tabs being on an opposite side of the host PCB from the third tab, the first to third tabs being on a same side of its antenna PCB, an amplitude taper on each antenna PCB at transitions between the host and antenna PCBs, including: a first transmission line splitting off into a second transmission line and a third transmission line, the second transmission line feeding two antennas to form one dipole pair, the third transmission line stepping down using a quarter-wave transformer, and a radio frequency (RF) connector to receive a power supply.