PhD defense - Muhammad Aziz Ul Haq

Geometry Modification Assessment and Design Optimization of Miniaturized Wideband Antennas

  • 17.5.2019, 14:00 - 15:00

The PhD defense of Muhammad Aziz Ul Haq will be held on Friday the 17th of May at 14:00 in room V104.

Title of thesis: Geometry Modification Assessment and Design Optimization of Miniaturized Wideband Antennas

Candidate: Muhammad Aziz Ul Haq

Date and time: 17th of May 2019 at 14:00

Room: V104

Thesis Committee:
Slawomir Koziel, Professor, and Supervisor, Reykjavík University
Ágúst Valfells, Dean of School of Science and Engineering, Reykjavík University
Eyjólfur Ingi Ásgeirsson, Associate Professor, Reykjavík University
Kristján Leósson, General Manager, Innovation Center Iceland

Examiner: Ivor Morrow, Senior Lecturer, Cranfield University, UK

Abstract:

Maintaining small physical dimensions of antenna structures is an important consideration for contemporary wireless communication systems. Typically, antenna miniaturization is achieved through various topological modifications of the basic antenna geometries. The modifications can be applied to the ground plane, the feed line, and/or antenna radiator. Unfortunately, various topology alteration options are normally reported on a case-to-case basis. The literature is lacking systematic investigations or comparisons of different modification methods and their effects on antenna miniaturization rate as well as electrical performance. Another critical issue—apart from setting up the antenna topology—is a proper adjustment of geometry parameters of the structure so that the optimum design can be identified. Majority of researchers utilize experience-driven parameter sweeping which typically yields designs that are acceptable, but definitely not optimal. Furthermore, in many of the cases, the authors provide a cooperative progression before and after topological modifications that generally lead to a certain reduction of the antenna size, however, with appropriate parameter adjustment missing. Consequently, suitability of particular modifications in the miniaturization context is not conclusively assessed. In order to carry out such an assessment in a reliable manner, identification of the truly optimum design is necessary. This requires rigorous numerical optimization of all antenna parameters (especially in the case of complex antenna topologies) with the primary objective being size reduction, and supplementary constraints imposed on selected electrical or field characteristics. This thesis is an attempt to carry out systematic investigations concerning the relevance of geometry modifications in the context of wideband antenna miniaturization. The studies are carried out based on selected benchmark sets of wideband antennas. In order to ensure a fair comparison, all geometry parameters are rigorously tuned through EM-driven optimization to obtain the minimum footprint while maintaining acceptable electrical performance. The results demonstrate that it is possible to conclusively distinguish certain classes of topology alterations that are generally advantageous in the context of size reduction, as well as quantify the benefits of modifications applied to various parts of the antenna structure, e.g., with feed line modifications being more efficient than the ground plane and radiator ones. Several counterexamples have been discussed as well, indicating that certain modifications can be counterproductive when introduced ad hoc and without proper parameter tuning. The results of these investigations have been utilized to design several instances of novel compact wideband antennas with the focus on isolation improvement and overall antenna size reduction in multi-input-multi-output (MIMO) systems. Experimental validations confirming the numerical findings are also provided. To the best of the author’s knowledge, the presented study is the first systematic investigation of this kind in the literature and can be considered a step towards the development of better, low-cost, and more compact antennas for wireless communication systems.