THE SHAPE SYNTHESIS OF DIELECTRIC RESONATOR ANTENNAS FOR WIRELESS COMMUNICATION SYSTEMS

Open Access
Author:
Alroughani, Hamad
Graduate Program:
Electrical Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
August 03, 2018
Committee Members:
  • James Kenneth Breakall, Dissertation Advisor
  • James Kenneth Breakall, Committee Chair
  • Ram Mohan Narayanan, Committee Member
  • Julio Urbina, Committee Member
  • Antonios Armaou, Outside Member
Keywords:
  • Shape optimizations
  • dielectric resonator antennas
  • material properties characterization
  • characteristic modes
  • antenna shape synthesis
  • method of moments
  • surface integral equations
  • volume integral equations
  • additive manufacturing
  • MIMO.
Abstract:
Antennas are needed in wireless communications of any kind and are key to the quality of any wireless link, irrespective of its use. The abilities needed of a particular antenna depend on its application, and so the cost of antennas in current use varies from a few cents for those in mobile devices, to many millions of dollars for the main mission antennas on satellites or sophisticated radar antennas in military use. They are indeed the eyes and ears of modern wireless communications systems. Dielectric resonator antennas are one of the popular antenna types and hold the promise of requiring less room for proper operation, in essence due to the loading effect of the material. The principal original contributions to antenna shape synthesis is presented in this dissertation; an approach is devised for the three-dimensional shape synthesis of dielectric resonator antennas which are subject to geometry restrictions. It is entirely new, representing the first time any three-dimensional shape optimization of dielectric resonator antennas has been described. It is particularly novel because, not only does it shape the dielectric material, but it permits the shape optimization process to proceed without the restriction of a pre-determined feed-point location. The approach is made possible through properly connecting antenna performance parameters to the use of characteristic mode concept which allows the computation of modal weighting coefficients using the surrogate source idea that is established. These coefficients are then used in the definition of the objective functions. The shape synthesis technique was successfully applied to three dielectric resonator antenna examples, each with different design requirements and constraints. Its success in these cases demonstrates the effectiveness of the new shaping technique. Computed performance is supported by experimental results. The implementation of the shaping tool itself, apart from being needed to validate the shaping process, is an addition in its own right. It has purposefully been fully implemented using commercially available software, for the computational electromagnetics, the optimization algorithm, and the controller that manages the shaping process and allows communication between the various steps. The advantage of being able to use such commercial codes is that the approach at once becomes more accessible to others. The determination of the characteristic modes of dielectric objects has been fraught with difficulties, and there have been uncertainties in the literature as to precisely what was being computed. A number of aspects of characteristic mode theory therefore had to be investigated and repaired before the shape synthesis work could proceed. Although they might not be linked directly to the shape synthesis process, other significant contributions are related to the characteristic mode analysis by developing a more robust method for tracking the characteristic modes of dielectric objects, presenting a more general (broadened) formulation of the sub-structure characteristic mode concept and providing formal mathematical proofs of the orthogonality properties of sub-structure modes.