Development of Polarization/Pattern Reconfigurable Antennas for Wireless Applications

Abstract

The rapid advancement of wireless communication technologies, especially with the rise of 5G and the Internet of Things (IoT), necessitates antenna designs that are adaptable, efficient, and able to accommodate a variety of operational requirements. Reconfigurable antennas, which provide capabilities like polarization agility, beam pattern switching, and frequency tunability, have become essential components in meeting these requirements. This thesis examines the development of reconfigurable antennas designed specifically for sub-6 GHz frequency bands, addressing the demand for compact, adaptable, and high-performance solutions in contemporary wireless systems. Conventional antenna designs encounter challenges in fulfilling the diverse operational requirements of contemporary wireless systems, particularly in maintaining compactness with multi-functionality. Conventional fixed antennas often lack the necessary adaptability to deal with dynamic environments, leading to constraints on data rates, signal quality, and interference mitigation. Furthermore, the integration of multiple-input multiple-output (MIMO) configurations with reconfigurability introduces challenges, such as increased complexity, higher losses, and reduced isolation, which adversely affect the performance in densely packed frequency bands like sub-6 GHz. Moreover, the existing reconfigurable antenna designs often experience increased complexity, high power consumption, and reduced performance, which hinder their practical implementation in compact wireless systems. This thesis offers a thorough approach to tackle these challenges through the design and optimization of diverse reconfigurable antenna configurations for the sub-6 GHz band. Polarization reconfigurable antennas are designed to enhance signal robustness, whereas pattern reconfigurable antennas focus on improving directional coverage and managing interference. Hybrid reconfigurable antennas integrate various functionalities to enhance adaptability. Furthermore, polarization reconfigurable MIMO antennas and pattern reconfigurable MIMO antennas are introduced to provide improved data rates and spatial diversity while maintaining compact designs and effective isolation. The thesis follows a progressive workflow, beginning with the development of a polarization reconfigurable antenna that includes a slotted ground plane design, demonstrating LP and LHCP and an AMC-integrated antenna, demonstrating reliable LP, LHCP, and RHCP switching for sub-6 GHz 5G applications. Building on this, a compact pattern reconfigurable antenna is introduced, utilizing semi-circular and elliptical patch structures with PIN diodes to enable directional control without compromising size or performance. The research is further extended to hybrid reconfigurable antennas, combining frequency and pattern reconfigurability, and achieving dual-band operation with optimized gain and efficiency. Finally, the work culminates in advanced MIMO antenna designs, supporting polarization and pattern reconfigurability, high port isolation, low ECC (<0.5), and other diversity metrics such as DG, MEG, and TARC. Each chapter is interlinked, illustrating a comprehensive workflow from single-element reconfigurable designs to MIMO systems, validated through both simulation and experimental results, and ultimately targeting practical deployment in 5G wireless networks. The designs utilize efficient switching mechanisms, advanced materials, and optimization techniques to fulfil performance requirements while maintaining compactness and minimizing complexity. Several reconfigurable modes of the proposed designs are simulated, fabricated, and tested. CST-MWS (Computer Simulation Technology Microwave Studio) software is used for all of the proposed work's simulations, while VNA and anechoic chambers are taken into consideration for measurement. The effectiveness of the suggested antennas in providing improved performance is demonstrated by key outcomes from both simulated and measured data, such as strong impedance matching across the intended frequency ranges and stable radiation patterns across different operating conditions. By providing feasible solutions to the changing needs of contemporary wireless systems, this research advances the expanding field of reconfigurable antenna design and eventually supports reliable and efficient communication.