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2.2 ELECTRICAL, ELECTRONIC, INFORMATION ENGINEERING
Millimeter-wave frequencies are anticipated to be widely adapted for future wireless communication systems to resolve the demand of high data-rate and capacity issues. The millimeter-wave frequency range offers wide spectrum and a shift for most newly developing technologies as the microwave and lower frequency bands are becoming overcrowded and congested. These high frequency bands offer short wavelengths which has enabled the researchers to design and implement compact and adaptable antenna solutions. This research focuses on the implementation, transformation and modification of antenna structures used in lower frequency bands to millimeter-wave applications with high gain and multi-band and wideband performances.
The first part of the thesis presents a microstrip patch array antenna with high gain in the upper 26 GHz range for 5G applications. The tolerance of the antenna, on widely used Rogers RT/duroid 5880 substrate, is observed with the edge-fed structure when curved in both concave and convex directions.
In the second part of the thesis, 20 rectangular loops are arranged in a quasi-rhombic shaped planar microstrip grid array antenna configuration with dual-band millimeter-wave performance. A comparison with equal sized microstrip patch array is also presented to analyse the performance. The antenna operates in the upper 26 GHz band and has two frequency bands in close proximity.
The third part of the thesis discusses the transition from wire Bruce array antenna to planar technology. Having been around for nearly a century and despite the simplicity of structure, the research community has not extended the concept of Bruce array antenna for further research. The proposed planar Bruce array antenna operates in three frequency v bands with optimization focus on 28.0 GHz band that has a directive fan-beam radiation pattern at broadside whereas the other two frequency ranges, above 30 GHz, have dual-beam radiation patterns which provide radiation diversity in narrow passages.
The final part of the thesis deals with the transformation and modification of wire Bruce array antenna geometry to edge-fed printed leaky-wave antennas for millimeter-wave frequency scanning applications. In the first approach, the lengths of the unit-cell are optimised, without any additional circuitry, to enable two scanning ranges and mitigate the Open-Stopband, at broadside, for seamless scanning in the first range. A Klopfen-stein tapered divider is then deployed to make a linear array of the proposed antenna to achieve high gain. In the second approach, the horizontal and vertical lengths of the meandered unit-cell are replaced with semi-circular and novel bowtie elements, respectively, to obtain wide scanning range.
The numerical results and optimizations have been performed using CST Micro-wave Studio where the effects of metallization and dielectric losses are properly consid-ered. The prototypes of the proposed antennas have been fabricated and experimentally validated.
Ahmed, Z. (2021). Study of mm-wave Fixed Beam and Frequency Beam-Scanning Antenna Arrays. Technological University Dublin. doi: 10.21427/JMSY-GE93
Science Foundation Ireland