Saudi Cultural Missions Theses & Dissertations
Permanent URI for this communityhttps://drepo.sdl.edu.sa/handle/20.500.14154/10
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Item Restricted Metasurface-Augmented Gradient-Index Lenses for Millimetre-Wave Applications(Queen's University Belfast, 2025-09) Alali, Bader Saad; Zelenchuk, Dmitry; Abbasi, Muhammad Ali BabarThis research project aims to develop metasurface-augmented gradient index (GRIN) lenses for millimetre-wave (mmWave) applications. It introduces a concept combining GRIN lenses with metasurfaces, enhancing the ability to direct beams of high-gain GRIN lens antennas and control focal positions in GRIN lens beamformers. A novel methodology for designing the metasurface is established by analysing the electric field phases within a GRIN lens along with the phase shift in a single unit cell, using full-wave simulation tools available to researchers. The research investigates two GRIN lenses: the 2D Luneburg lens antenna and the 2D Maxwell fisheye lens (MFL) beamformer in reflective and transmit modes. By integrating a half-circle Luneburg lens antenna with a variable-sized square patch reflectarray, beamsteering with a maximum angle of 75° was achieved across a frequency range of 26 – 28 GHz. The operational bandwidth extended to 24 – 38 GHz with a wideband Phoenix reflectarray. The half-circle Maxwell fisheye lens (HMFL) beamformer maintained its focal axis and achieved a maximum angle of 45° within a frequency range of 26 – 28 GHz. This was extended to 22 – 32 GHz using the Phoenix reflectarray. Both lenses were evaluated at normal incidence (0°) and oblique incidences (-15° and -30°). In transmit mode, the GRIN lenses were modified with an all-dielectric phase correction layer composed of cubic unit cells. This layer, placed vertically between two half-circle lenses, formed a 2D circular transmitarray-augmented Luneburg lens antenna, generating directive beams with a maximum angle of 75° across 24 – 30 GHz. The MFL beamformer, combined with the phase correction layer, focused incident energy, achieving a maximum angle of 45° across 22 – 32 GHz. This research explores 3D printing techniques for fabricating GRIN lenses and transmitting metasurfaces and printed circuit board (PCB) technology for the reflective metasurfaces, enabling cost-effective laboratory prototype production.35 0Item Restricted Low Cost Transparent and Flexible Antenna for Next Generation Communication Networks(University of Illinois at Chicago, 2024-02-09) Alsaab, Nabeel; Chen, Pai-YenNext-generation antenna design plays a vital role in enabling technologies in fifth generation (5G) and beyond fifth-generation (B5G) wireless networks. 5G and B5G technologies are envisioned to provide ubiquitous connectivity, enhanced coverage, ultra reliable low latency, and high data rates to meet societal and industrial needs. Furthermore, they are envisioned to unleash the potential of machine-to-machine communication and internet-of-things (IoTs) to build an ecosystem where networks can provide instantaneous connectivity for billions of connected devices. However, one challenge to the wide deployment of such a level of connectivity is that traditional antennas used in the current 4G and 4G-LTE systems are often large and intrusive. The exponential growth in demand for IoT devices, gateways and other wireless modulus, alongside with aesthetics requirement and cost considerations, have driven engineers to research “invisible” optically- transparent antennas and arrays that can be used in access points and signal repeaters embedded into existing urban infrastructure, without spoiling the aesthetic appearance of the environment and architectures. This thesis focuses on development of robust, cost-effective, and ecologically acceptable nanomaterials for optically transparent antennas, intelligent surfaces, and radio-frequency (RF) devices. Particularly, a large- area, ultralow-profile and mechanically-flexible transparent conductive films (TCFs) based on the metal-dielectric nanocomposite (MDNC) will be used to build these key component in next- generation communication systems. Moreover, the optimal design of MDNC, which exhibits high optical transparency and decently low electrical resistivity, will be conducted using the optical nanocircuit theorem and transfer matrix method. The versatility of the MDNC-TCF is demonstrated by implementing various transparent and flexible antennas, in the form of omnidirectional linear dipole, unidirectional Yagi-Uda antenna, microstrip patch antenna, and novel solar-powered body-wearable antenna. This research also studies transparent metasurfaces and their applications in antenna radomes, which can be used in, for example, high-gain and low- RCS Fabry-Perot cavity antennas and solar-powered base station antenna. The results of this thesis will pave the way for the practical realization of low-cost, conformal and optically- transparent antennas and intelligent surfaces that are capable of enhancing and optimizing connectivity of 5G and B5G communication systems.22 0