Flexible Antenna Design for 5G Applications
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Recent advancements in the fifth generation (5G) technology and internet of things (IoT) along with the development of printed electronics (PE) have inspired flexible antenna designs, which feature low-profile and low-cost. They open the door to extend wireless communication to support wearable applications on conformal curvature surfaces in the context of wireless personal area networks (WPANs). Most of current existing antenna design focus on traditional materials and fabrication methods, yielding rigid metallic structures, which makes them not suitable for applications with flexible and conformal surfaces, let alone the WPAN applications. Therefore, this thesis focuses on antenna designs with a promising flexible structure, which can be fabricated with proper methods and materials and applied to curvature surfaces. Firstly, a comprehensive literature review, including ink-printed antennas and their fabrication techniques is presented. Next, three low-profile planar antennas are proposed with flexible dielectric substrates, which are suitable for fabrication using modern printing technologies. These antennas include a microstrip slot antenna operating at 5.8 GHz, a triband microstrip patch antenna with multiple slots operating at 5.8 GHz, 6.2 GHz, and 8.4 GHz, and a wideband dipole array antenna whose operating frequency covers 24.5 GHz and 28 GHz in industrial, scientific and medical (ISM) band. The above antennas demonstrate promising measured and simulated performance, acceptable tolerance in the conformal tests, and positive specific absorption rate (SAR) when interacting with human body part. Furthermore, a metasurface based S-shaped split ring resonator (SRR) linear-to-circular (LTC) polarization converter is presented to enhance the gain and bandwidth of planar patch and slot antennas. Its performance in curvature situation is evaluated as well. These antenna designs proposed in this thesis provide a deeper insight into flexible low-profile planar antenna design for curvature surfaces and add to the rapidly expanding field of WPAN applications. In addition, they have important practical implications for fabrication using printing technologies. Moreover, the results and findings in this thesis contribute to existing knowledge of the interaction between antennas and the human body.