This dissertation focuses on the development of next generation wireless communications at millimeter-wave and sub-terahertz frequencies. As wireless providers experience a bandwidth shortage and cellular subscribers demand faster data rates and more reliable service, a push towards unused carriers fre- quencies such as 28 GHz, 60 GHz, and 180 GHz will alleviate network conges- tion while simultaneously providing massive bandwidths to consumers. This dissertation summarizes research in understanding millimeter-wave wireless propagation, the design and fabrication of millimeter-wave and sub-terahertz on-chip antenna arrays on an integrated circuit semiconductor process, and the accurate measurement of on-chip antenna radiation patterns in a wafer probe station environment. / text

This thesis investigates omnidirectional and directional ultra wideband (UWB) antennas for communication and microwave imaging applications. To reduce interference with existing technologies, monopole antennas with efficient band-stop functions are introduced. Single and double slots acting as series resonators are used. Reduction in the antenna gain in the stop-band regions of about 19.5 dB is achieved. Central metal removal and ground plane size effects on the antenna performance are investigated. To eliminate signal distortion caused by such monopole antennas, phase centre behaviour over the entire frequency band of operation is investigated at different principle planes, which have not been done before. This study will also show how these antennas act in different communication scenarios and where the radiation will be coming from at different frequencies. The effect of including different slots with different shapes on the performance of phase centre of these antennas is also investigated. Different methods to minimize the antenna phase centre movement are studied. Novel microstrip antennas with UWB impedance and radiation pattern bandwidth and low cross polarization components are introduced to work over the frequency band from 3 to 20 GHz. The antennas introduced are double-layer structures in which the radiator is sandwiched between two identical partial ground planes or a partial ground plane is sandwiched between two radiators. Results show a significant reduction in the cross polarization components at all frequencies. A novel high gain UWB Vee dipole antenna with a UWB coaxial balun feed is introduced to cover the existing and future UWB communication applications. Different type of loadings such as a reflecting ground below the antenna, a dielectric sleeve over the UWB balun and conical dielectrics between the Vee plates are also used and studied that show enhanced gains and lower sidelobes. A miniaturized-type UWB Vee dipole antenna is also investigated for microwave imaging applications. The antenna has a small radiation aperture which makes it a good candidate for array type applications. Full wave analysis of studied antennas are done using Ansoft HFSS, finite-element-methods based software. Experimental investigations are done to confirm the accuracy of simulated results.

Wireless communication systems continue to face the challenge of time varying quality of the underlying communication channel. When a slow fading channel goes into a deep fade, the corresponding communication system might face successive decoding failures at the destination, and for delay-sensitive communication systems, this amounts to delays that are not desired. In such situations, it becomes a priority to get out of the deep fades. Many techniques and approaches are already available in the literature to counteract fading effects. This work is motivated by recent advances in fast reconfigurable antennas, which provide new means to change the statistical profile of fading channels, and hence reduce the probability of prolonged fades. Fast reconfigurable antennas are poised to improve overall performance, especially for delay-sensitive traffic in slow-fading environments. This potential enhanced performance motivates this study of the queueing behavior of point-to-point communication systems with reconfigurable antennas. We focus on finite-state channels with memory, and we analyze the queueing behavior of the wireless communication system over erasure channels, for a traditional system versus a reconfigurable antenna implementation. We provide numerical results for situations where using reconfigurable antennas yield substantial performance gains in terms of throughput, delay and buffer overflow.

This thesis investigates omnidirectional and directional ultra wideband (UWB) antennas for communication and microwave imaging applications. To reduce interference with existing technologies, monopole antennas with efficient band-stop functions are introduced. Single and double slots acting as series resonators are used. Reduction in the antenna gain in the stop-band regions of about 19.5 dB is achieved. Central metal removal and ground plane size effects on the antenna performance are investigated. To eliminate signal distortion caused by such monopole antennas, phase centre behaviour over the entire frequency band of operation is investigated at different principle planes, which have not been done before. This study will also show how these antennas act in different communication scenarios and where the radiation will be coming from at different frequencies. The effect of including different slots with different shapes on the performance of phase centre of these antennas is also investigated. Different methods to minimize the antenna phase centre movement are studied. Novel microstrip antennas with UWB impedance and radiation pattern bandwidth and low cross polarization components are introduced to work over the frequency band from 3 to 20 GHz. The antennas introduced are double-layer structures in which the radiator is sandwiched between two identical partial ground planes or a partial ground plane is sandwiched between two radiators. Results show a significant reduction in the cross polarization components at all frequencies. A novel high gain UWB Vee dipole antenna with a UWB coaxial balun feed is introduced to cover the existing and future UWB communication applications. Different type of loadings such as a reflecting ground below the antenna, a dielectric sleeve over the UWB balun and conical dielectrics between the Vee plates are also used and studied that show enhanced gains and lower sidelobes. A miniaturized-type UWB Vee dipole antenna is also investigated for microwave imaging applications. The antenna has a small radiation aperture which makes it a good candidate for array type applications. Full wave analysis of studied antennas are done using Ansoft HFSS, finite-element-methods based software. Experimental investigations are done to confirm the accuracy of simulated results.

Errata inserted inside back end-paper. / Bibliography: p. 243-249. / xvi, 249 p. : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis presents a brief overview of microstrip antenna analysis and describes the connections between spectral and spatial domain periodic Green's functions in integral equation methods. A hybrid formulation is applied to a variety of problems from simple metal strip dipoles to more complicated microstrip geometries. A further development to finite array analysis is described. An improvement in the accuracy of this approximative technique is explored. / Thesis (Ph.D.)--University of Adelaide, Dept. of Electrical and Electronic Engineering, 1997

Errata inserted inside back end-paper. / Bibliography: p. 243-249. / xvi, 249 p. : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis presents a brief overview of microstrip antenna analysis and describes the connections between spectral and spatial domain periodic Green's functions in integral equation methods. A hybrid formulation is applied to a variety of problems from simple metal strip dipoles to more complicated microstrip geometries. A further development to finite array analysis is described. An improvement in the accuracy of this approximative technique is explored. / Thesis (Ph.D.)--University of Adelaide, Dept. of Electrical and Electronic Engineering, 1997

Thesis (Ph.D.) -- University of Western Sydney, 2001. / "Submitted in fulfilment of requirements for the degree of Doctor of Philosophy, School of Engineering and Industrial Design, University of Western Sydney" Includes bibliography.

Thesis (Ph.D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Manos M. Tentzeris; Committee Co-Chair: John Papapolymerou; Committee Member: Andrew F. Peterson; Committee Member: Chang-Ho Lee; Committee Member: John D. Cressler; Committee Member: Joy Laskar.

Thesis (MEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Balanced loads such as antennas normally require baluns when they are measured. For wide band applications, designing and building a balun complicates the measurement and introduces errors. A simple model for load impedances was developed, together with a novel measurement procedure. The procedure enables the measurement of balanced loads using a network analyzer with no balun. Measured and simulated results are presented. / AFRIKAANSE OPSOMMING: Gebalanseerde laste soos antennas benodig gewoonlik balons om korrek gemeet te word. Die ontwerp van 'n balon vir wye band toepassings bemoeilik die metings en veroorsaak foute. 'n Eenvoudige model vir die lasimpedansies is ontwikkel sowel as 'n eenvoudige meetmetode. Die metode word gebruik om die gebalanseerde laste te meet met 'n netwerk analiseerder sonder die gebruik van 'n balon. Gemete en gesimuleerde resultate word getoon.

Submitted by Lara Oliveira (lara@ufersa.edu.br) on 2017-07-06T20:43:45Z No. of bitstreams: 1 SamantaMH_DISSERT.pdf: 5589913 bytes, checksum: 13f8ab4185b2d9b1c9576d1b7fd6d94b (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-07-18T15:04:50Z (GMT) No. of bitstreams: 1 SamantaMH_DISSERT.pdf: 5589913 bytes, checksum: 13f8ab4185b2d9b1c9576d1b7fd6d94b (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-07-18T15:05:35Z (GMT) No. of bitstreams: 1 SamantaMH_DISSERT.pdf: 5589913 bytes, checksum: 13f8ab4185b2d9b1c9576d1b7fd6d94b (MD5) / Made available in DSpace on 2017-07-18T15:05:42Z (GMT). No. of bitstreams: 1 SamantaMH_DISSERT.pdf: 5589913 bytes, checksum: 13f8ab4185b2d9b1c9576d1b7fd6d94b (MD5) Previous issue date: 2016-12-01 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The growing development of telecommunications, especially mobile devices, has intensified related searches the microstrip antennas in recent years since they have unique properties and wide range of applications. The constant demand for lighter and more flexible devices boosted research in wearable technology area where electronics are fully embedded in their fibers. In this context, knitted fabrics have the necessary elasticity to create adaptable and sports parts, enabling high mobility and comfort to its users. The textile antennas are malleable and, therefore, have great utility in applications where rigidity of traditional antennas is considered limiting, as in military use clothing and in the biomedical field. This work aims to study and develop microstrip antennas using knitted fabric based composite fibers, showing the procedures and materials used from the characterization and choice of fabrics to the design, manufacture and testing of the textile antenna. The electrical characterization was carried out using a Vector Network Analyzer (ARV) to obtain the electrical properties (permittivity and tangent losses). Obtaining textile properties (weight, dimensional stability, degree and tensile strength) was made in accordance with the technical standards, using the equipment available at the Department of Textile Engineering at the Federal University of Rio Grande do Norte (UFRN). The antenna has been designed using the transmission line model of Fortran program developed in accordance with the electrical properties of textile substrates. Subsequently the antenna was designed and simulated in HFSS® (High Frequency Structural Simulator), where radiation patterns are obtained, return loss, the Smith chart, current density and gain. The best simulated result was implemented with tissue disposed knitted in a three-layer structure according to the dimensions designed, and then the antenna is tested using a spectrum analyzer, which were collected data that allowed the manufacture of the letter Smith and graph of return loss. The experimental data were compared with the simulated and the results analyzed according to the literature that support this paper / O crescente desenvolvimento das telecomunicações, principalmente a de dispositivos móveis, têm intensificado as pesquisas relacionadas as antenas de microfita nos últimos anos, visto que estas possuem propriedades singulares, bem como vasta gama de aplicações. A constante procura por dispositivos mais leves e flexíveis impulsionou as pesquisas na área de tecnologia vestível, onde componentes eletrônicos são inteiramente embutidos em suas fibras têxteis. Nesse contexto, os tecidos malha possuem a elasticidade necessária para criar peças adaptáveis e esportivas, permitindo alta mobilidade e conforto aos seus usuários. As antenas têxteis são maleáveis e, por essa razão, têm grande utilidade em aplicações onde a rigidez das antenas tradicionais é considerada uma limitação, como em roupas de uso militar e na área biomédica. Este trabalho tem como objetivo estudar e desenvolver antenas de microfita utilizando tecido de malha à base de fibras têxteis compostas, mostrando os procedimentos e materiais utilizados desde a caracterização e escolha dos tecidos até o projeto, confecção e testes da antena têxtil. A caracterização elétrica foi realizada através de um Analisador de Redes Vetorial (ARV) para obtenção das propriedades elétricas (permissividade e tangente de perdas). A obtenção das propriedades têxteis (gramatura, estabilidade dimensional, titulação e resistência a tração) foi feita de acordo com as normas técnicas, utilizando os equipamentos disponíveis no Departamento de Engenharia Têxtil da Universidade Federal do Rio Grande do Norte (UFRN). A antena foi dimensionada através do modelo da linha de transmissão em programa desenvolvido na linguagem Fortran de acordo com as propriedades elétricas dos substratos têxteis. Posteriormente a antena foi desenhada e simulada no HFSS® (High Frequency Structural Simulator), onde serão obtidos os diagramas de radiação, perda de retorno, densidade de corrente e ganho. O melhor resultado simulado foi implementado com o tecido de malha disposto numa estrutura de três camadas de acordo com as dimensões projetadas e, em seguida, a antena foi testada através de um analisador de espectro, onde foram coletados dados que permitiram a confecção da carta de Smith e gráfico da perda de retorno. Os dados experimentais foram comparados com os simulados e, os resultados analisados de acordo com a literatura especializada que embasam este trabalho / 2017-07-06