In this thesis the design and build of a high-speed, video-rate optical coherence tomography (OCT) imaging system is described. The system was designed for the purpose of imaging human skin in vivo, particularly that of patients suffering from conditions such as systemic sclerosis. Component selection and design decisions are discussed in the context of the intended final application. Initial test images from the system are presented. In the context of building an OCT system, a supercontinuum light source was characterised and tested for its suitability for use in the OCT environment. Parameters such as coherence length were measured using simple interferometry techniques, while practical considerations such as portability and ease of system integration were also considered.Several applications of OCT imaging techniques were also investigated, using two commercially-available OCT systems from Thorlabs, Inc. A liquid-based skin and blood flow model was constructed using narrow glass capillary tubes, pumped through with scattering solutions of Intralipid or suspensions of polystyrene microspheres. The concentration of the solutions was tuned by dilution in order to best model the scattering parameters of blood. The model also used similar liquid solutions to model static tissue surrounding the blood vessels. Doppler OCT images of the model under various conditions were recorded, and velocity profiles of the flowing liquids were extracted.Using the same commercial OCT systems, imaging over two separate wavelength regions was also performed on the skin of several different species of neo-tropical tree frog, some of which have interesting reflective properties due to the presence of a pigment called pterorhodin. Cross-sectional OCT images of the skin are presented, and averaged depth profiles extracted from them. This is the first time that OCT imaging has been applied to this problem.A clinical study of skin thickening and microvascular function in patients with systemic sclerosis compared to healthy controls was also carried out, again involving a Thorlabs, Inc. commercial OCT system. This study was carried out at Salford Royal Hospital under the supervision of the rheumatology research group. Skin thickness was assessed using OCT and high-frequency ultrasound imaging. Microvascular function was measured using nailfold cappilaroscopy and laser Doppler imaging. Images from the study are presented here.

The global consumption of fossil fuels continues to increase due to the rapid growth of energy demand, as a consequence of expanding population and human activities. Fast climate change is another inescapable issue caused by humans that need to be addressed. The development of solar energy conversion technologies is widely considered as one of the most promising solutions to sustainably maintain a modern lifestyle of the society and create a carbon-neutral social development operation mode. The solar energy is carried and delivered in the form of electromagnetic fields. Therefore, the efficiency of photon collection is the primary factor to create any solar energy conversion systems. Through the inspiration from nature, the functionalized disorder, with a specific design and engineering, can introduce unusual light-matter interaction behaviors, and thus offer a potential capability to achieve perfect light harvesting. In my thesis, we develop complex Epsilon-Near-Zero (ENZ) metamaterials that can be used either as light capturing networks or the photoactive media by turning the energy damping ratio between radiative and non-radiative channels. We successfully integrate it into thin-film photovoltaic modules with showing an excellent performance enhancement led by broadband light localization effect. Thanks to universal of such complex ENZ metamaterials, with combining a thin layer of dielectric, we further develop efficient hot-carriers driven plasmonic photo-catalysts for artificial green chemical fuel synthesis. The detailed theoretic analysis is presented in this work.

This study dealt with the issue of sustainability of ICT4D initiatives being a problem with few success stories (Heeks, 2002, Toyama, 2010). Many of these initiatives were planned and executed in a top-down fashion by large funders and governments, and these failures have stimulated the search for new strategies to achieve long-term sustainability. One possible approach is to consider the different levels of systems that are involved. The reasons for failure lie inside the scope of a project, within the community itself, and outside the community in the larger socio-economic system which includes the economy. A systems approach with respect to the analysis of the sustainability (or lack thereof) of development initiatives was therefore adopted. The Choice Framework of Dorothea Kleine (2010) was used since it is a systemic approach, developed in the study of ICT4D initiatives, that embraces the complexity of engaging with development paradigms, societal structures and personal agency. The research was done on a large South African government initiative, the Broadband-for-All (BB4All), community-based wireless mesh network project which aimed to provide a cost-effective way of enabling reliable broadband connectivity in rural areas. The project had two key aspects, the provision of a large-scale demonstrator of a wireless mesh network (WMN) as a broadband solution and the establishment of a Village Operator (VO) model to support access to and increase the use of the technology. The teachers and learners in more than 170 schools were the primary customers. Young people from local communities were trained as VOs to become local entrepreneurs (micro-enterprises) responsible for operating and supporting the BB4All service in their assigned cluster of schools and respective communities. The research focus was the sustainability of the VOs. The Choice Framework was used to provide a context for the research regarding the role played by social resources (social capital) in contributing to the sustainability of the VO micro-enterprises. In-depth interviews were held with all but one of the 15 VOs in order to develop an understanding of their social capital and the influence thereof on them as entrepreneurs. The importance and usefulness of social capital in supporting sustainability at VO and initiative level was analysed. Three major themes emerged that were analysed in detail, namely, the role of social capital, community service and social entrepreneurship, as well as the development of networks of innovation. At a theoretical level, the research reflected on implications of the findings for the role of social capital in the Choice Framework. At a practical level, considerations for using a social capital perspective in order to improve the conceptualisation, design, implementation and transfer of ICT4D initiatives for sustainability were developed. / Thesis (PhD)--University of Pretoria, 2016. / Informatics / PhD / Unrestricted

The purpose of this thesis is to investigate how fixed broadband will be used in Swedish households in a 3-6-year perspective. Internet is becoming more and more integrated in peoples everyday lives. Internet is utilized for communication, entertainment and businesses to mention a few, and the areas of use are continuously expanding. How this expansion might affect the household usage patterns and what these possible changes will require from a fixed broadband connection are continuous questions in need of investigation to ensure that ISPs are able to provide services in line with market demand. By studying Internet adoption and consumption behavioral trends combined with development of fixed broadband up until present day, the thesis will serve as a basis for what the future might hold. These findings were then complemented with insights from market active experts together with adjacent research on future broadband connectivity, and compiled into a possible projection for fixed Swedish household broadband. The findings show that, with increasing societal integration, Internet is commonly viewed more and more as a commodity; a societal necessity rather than an, as previously viewed, additional service. Furthermore, the increasing speed trend remains but might wane within 10 years as development further than so, with consistent rate, will heavily exceed any imaginable future bandwidth utilization. Consequently, the idea of a normalized broadband, sufficient for the vast majority of household consumers is discussed as possibility from a 3-6 year perspective. / Syftet med denna studie är att undersöka, i ett 3-6 års perspektiv, hur fast bredband kommer att användas i svenska hushåll. Internet är allt mer integrerat i vårt dagliga liv. Internet används för kommunikation, underhållning och företagande för att nämna några exempel, och användningsområdena är ständigt växande. Hur denna expansion kan påverka hushållens användningsmönster och vad dessa eventuella förändringar kommer att kräva från en fast bredbandsanslutning är kontinuerliga frågor i behov av utredning för att se till att Internetleverantörer kan tillhandahålla tjänster i linje med marknadens efterfrågan. Genom att studera Internetvanor och konsumtionstrender i kombination med utvecklingen av fast bredband fram till idag, skapades en grund för vad framtiden skulle kunna medföra. Dessa slutsatser kompletteras sedan med insikt från marknadsaktiva experter samt med närliggande forskning om framtida bredbandsanvändning, och sammanställdes till en trolig prognos för fast bredband i svenska hushåll. Resultaten visar att med ökande samhällsintegration, ses Internet allt mer som en grundläggande samhällstjänst snarare än en, som det hittills betraktats, privat tilläggstjänst som man väljer eller avstår ifrån av olika anledningar. Utvecklingen mot ännu snabbare bredband fortsätter, men bör avta inom 10 år då utveckling längre än så i samma takt kommer grovt överskrida all tänkbar framtida bandbreddsutnyttjande. Följaktligen diskuteras möjligheten av ett normaliserat bredband, omfattande nog för majoriteten av alla hushållsanvändare inom ett 3-6 års perspektiv.

Surpassing the fundamental limits that govern all electromagnetic structures, such as reciprocity and the delay-bandwidth-size limit, will have a transformative impact on all applications based on electromagnetic circuits and systems. For instance, violating principles of reciprocity enables non-reciprocal components such as isolators and circulators, which find application in full-duplex wireless radios, radar, biomedical imaging, and quantum computing systems. Overcoming the delay-bandwidth-size limit enables ultra-broadband yet extremely-compact devices whose size is not fundamentally related to the wavelength at the operating frequency. The focus of this dissertation is on using time-variance as a new toolbox to overcome these fundamental limits and re-imagine circuit and system design. Traditional non-reciprocal components are realized using ferrite materials that loose their reciprocity under the application of external magnetic bias. However, the sheer volume, cost and weight of these magnet based non-reciprocal components coupled with their inability to be fabricated in conventional semiconductor processes, have limited their application to bulky and large-scale systems. Other approaches such as active-biased and non-linearity based non-reciprocity are compatible with semiconductor processes, however, they suffer from other poor linearity and noise performance. In this dissertation, using passive transistor switch as the modulating element, we have proposed the concept of spatio-temporal conductivity modulation and have demonstrated a gamut of non-reciprocal devices ranging from gyrators to isolators and circulators. Through novel circuit topologies, for the first time, we have demonstrated on-chip circulators with multi-watt input power handling, operation at high millimeter-wave frequencies, and tailor made circulators for emerging technologies such as simultaneous-transmit-and-receive MRI and quantum computing. Delay-bandwidth-size trade-off is another fundamental electromagnetic limit, that constrains the delay imparted by a medium or a device within a fixed footprint to be inversely proportional to the signal bandwidth. It is this limit that governs the size of any microwave passive devices to be inversely proportional to its operating frequency. As a part of this dissertation, through intelligent clocking of switched capacitor networks we overcame the delay-bandwidth-size limit, thus resulting in infinitesimal, yet broadband microwave devices. Here we proposed a new paradigm in wave propagation where the properties such as the propagation delay and characteristic impedance does not depend on the constituent elements/materials of the medium, but rather heavily rely on the user-defined modulation scheme, thereby opening huge opportunities for realizing highly-reconfigurable passives. Leveraging these concepts, we demonstrated wide range of reciprocal an non-reciprocal devices including ultra-compact delay elements, highly-reconfigurable microwave passives, ultra-wideband circulators with infinitesimal form-factors and dispersion-free chip scale floquet topological insulators. Application of these devices have also been evaluated in real-world systems through our demonstrations of wideband, full-duplex receivers leveraging switched capacitors based true-time-delay interference cancelers and floquet topological insulator based antenna interfaces for full-duplex phased-arrays and ultra-wideband beamformers. Furthermore, to cater the growing RF and microwave needs of future, large-scale quantum computing systems, we demonstrated a low-cryogenic, wideband circulator based on time modulation of superconducting devices. This superconducting circulator is expected to operate alongside the superconducting qubits, inside a dilution refrigerator at 10mK-100mK, thus enabling a tightly integrated quantum system. We also presented the design and implementation of a cryogenic-CMOS clock driver chip that will generate the clocks required by the superconducting circulator. Finally, we also demonstrated the design and implementation of a low-noise, low power consumption, 6GHz - 8GHz cryogenic downconversion receiver at 4K for cryogenic qubit readout.

Cette thèse vise à développer des antennes large bande à double polarisation avec un filtre et un dispositif d’adaptation d’impédance et d’alimentation intégrés, que nous avons définies comme antennes versatiles intriquées. La largeur de la bande et la double polarisation permettent d’utiliser l’antenne avec différents standards et donc d’être versatile. D'autre part, le filtre pour rejeter les harmoniques supérieurs et le réseau d'adaptation sont des parties intégrantes de l'élément rayonnant et lui confèrent le caractère intriqué. La première étude porte sur la conception d'une antenne large bande à double polarisation avec un filtre intégré dans le dispositif d’alimentation. Le filtre permet de rejeter les harmoniques indésirables. La structure complète est compacte et de dimensions 0.9 λ0x0.9 λ0, λ0 étant la longueur d’onde en espace libre à la fréquence basse. Afin d’augmenter la compacité, nous présentons ensuite une antenne à suppression des harmoniques (HSA : Harmonic Suppressed Antenna) large bande à simple et à double polarisation. Ce travail explore les différentes techniques utilisées pour concevoir une HSA. Dans cette approche, l'élément rayonnant, le filtre qui permet de rejeter le rayonnement d’harmoniques hors bande et le réseau d'adaptation, qui sont traditionnellement des circuits séparés, sont intégrés dans une seule unité compacte. La taille totale de l'antenne est 0.53 λ0x0.53 λ0. Le dernier chapitre présente une des HSA développées associée à un conducteur magnétique artificiel non-uniforme. Cette structure permet l’obtention d’une antenne large bande de faible épaisseur et directive. / This thesis aims to develop wideband antennas interrelated with a filter, which we have defined as versatile intricate antennas. The antenna is versatile as it provides wide bandwidth (more than one octave) and has the capability to generate two orthogonal polarizations. On the other hand, the filter for harmonic rejection and the matching network are integrated parts of the radiating element and give it the intricate character.The first study is concentrated on designing a dual polarized antenna with a wide stop filter integrated to the feeding network. This filter enables to reject harmonics and unwanted response. The complete structure is compact with a size of 0.9 λ0x0.9 λ0, λ0 being the free space wavelength at the lowest frequency. In order to improve the compactness of the whole system and to cover more standards, we present a single and dual polarized wideband Harmonic Suppressed Antenna (HSA). This work explores the different techniques used to design a HAS. The proposed antenna is simple in structure but versatile in applications. In this approach, radiating element, filter for harmonic rejection and matching network, which are traditionally separated circuits, are incorporated into a single compact unit. The total size of the antenna is 0.53 λ0x0.53λ0. The final chapter aims to study the previous intricate antenna with a new wideband Artificial Magnetic Conductor (AMC) structure as reflector in order to obtain a low profile and directive antenna.

Perception is a key feature in how any creature or autonomous system relates to its environment. While there are many types of perception, this thesis focuses on the improvement of the visual robotics perception systems. By implementing a broadband passive sensing system in conjunction with current perception algorithms, this thesis explores scene reconstruction and world modeling. The process involves two main steps. The first is stereo correspondence using block matching algorithms with filtering to improve the quality of this matching process. The disparity maps are then transformed into 3D point clouds. These point clouds are filtered again before the registration process is done. The registration uses a SAC-IA matching technique to align the point clouds with minimum error.  The registered final cloud is then filtered again to smooth and down sample the large amount of data. This process was implemented through software architecture that utilizes Qt, OpenCV, and Point Cloud Library. It was tested using a variety of experiments on each of the components of the process.  It shows promise for being able to replace or augment existing UGV perception systems in the future. / Master of Science

A limiting factor in the widespread deployment of LMDS systems is the limited distance of current systems. Rain attenuation and limited transmitter power are the primary causes of the limited distance. Adaptive digital predistortion is presented as a method of increasing effective transmitter power. A background on LMDS link design, non-linear amplification, and predistortion is presented to assist the reader. A developed simulation uses AM-AM and AM-PM characteristics obtained from laboratory measurements of a 28 GHz amplifier to determine the effect of several predistortion implementation options and to confirm the feasibility of the proposed architecture. The potential impact of this predistortion architecture on LMDS system design is considered. The presented multi-stage predistortion architecture is found to be capable of implementation at Msymbol/second rates utilizing a FPGA or custom IC and a moderate speed digital signal processor. / Master of Science

Yes / This study presents a compact broadband wide-slot antenna with broadband left-hand circular polarization compatible with both LTE 42 and LTE 43 standards of 5G mid-band applications. The proposed antenna is fabricated on an FR4 dielectric substrate with overall dimensions of , where is the free space wavelength at the resonant frequency of the antenna. The antenna ground plane is etched to form a square radiating slot with a pair of rectangular ground stubs that are diagonally placed inside the slot. On the other side of the antenna, the feed line is loaded by horizontal and vertical stubs to improve the coupling between the feed line and the square slot. To generate a circular polarization, the feeding stubs cooperate with the pair of rectangular ground stubs to excite the radiating slot of the antenna at two different feeding points whose currents have approximately equal amplitude and 90o phase shift. The measured impedance bandwidth (BW) of the proposed wide-slot antenna is 16.2% (580 MHz along the band 3.3-3.88 GHz), while the observed axial ratio bandwidth (ARBW) is 12.2% (440 MHz in the 3.4-3.84 GHz band). The measured gain values are found to be larger than 2.5 dB along both standards of the 5G mid-band applications. / This work was supported in part by the U.K. Engineering and Physical Sciences Research Council (EPSRC) under Grant EP/E022936/1, and in part by the European Union’s Horizon 2020 Research and Innovation Programme under Grant H2020-MSCA-ITN-2016 SECRET-722424.

Yes / This paper examines the case for an ultrawideband planar inverted-F-L-antenna design intended for use in the lower sub-band. The antenna construction is based on the conventional inverted F, and inverted L as its feed element, and parasitic element, respectively. The optimized antenna size is 30×15×4mm3. The prototype antenna has a good return loss of -10 dB, and a 66.6% impedance bandwidth (2.8 GHz ¿ 5.6 GHz), the gain varies between 3.1 dBi and 4.5 dBi.