Millimeter-Wave Antennas for 5G Communication Systems

Abstract

The human civilization is now living in an age where every aspect of their social lives tend to transform and merge into a digital domain. The amount of data created at every instant of time by an individual item or a person is immense. There is a dire need of intelligent computing systems that are smart, resilient and can communicate at lightning fast speeds. Ubiquitous connectivity for everyone is now a global requirement and the solution to it is the fifth generation of mobile communication systems or simply the 5G. This massive scale connectivity requires extremely large bandwidth for which the currently used spectrum at microwave regime is not sufficient. There is a huge amount of unused bandwidth available at millimeter-wave frequencies beyond 20 GHz that can be harnessed for ultra-high speed communication required in 5G. This thesis aims at exploring the viability of compact planar mobile phone antennas for operation in millimeter-wave 5G communication bands in the range of 20-40 GHz. This research work is done in order to realize various novel planar antenna structures with the objectives of accomplishing: high gain, large bandwidth, multi-band operation, dual-beam radiations and narrow beam-widths. At millimeter-wave frequencies, antennas have extremely compact structures and exhibit very small apertures. Obtaining large bandwidth and high gain thus becomes a challenging task. This thesis will show that large bandwidth and high gain can be attained via various different geometric design methodologies. Novel ways of minimizing mutual coupling between millimeter-wave antennas and providing techniques for fulfilling spatial diversity needs will be explored. These antenna structure geometries include spiral, hexagon and rhombus shapes for obtaining high-end performance. A special 4-way feed network for thin substrates is realized, analyzed and illustrated in detail for a broad millimeter-wave frequency range. Single element antennas are organized in array configurations and connected via this proprietary feed network to enhance their gains up to the desired 5G levels. A dual band antenna working on the principle of split ring and closed ring resonators covering 28 and 38 GHz bands has also been realized, analyzed and discussed in detail. Furthermore, a dual-beam antenna for spatial diversity application bearing a novel fractal snowflake geometry is presented and analyzed for the 28 GHz 5G band.