Yes / In this work, an analytical study of the electromagnetic propagation in a complex medium-based suspended three-layer coplanar waveguide (CPW) is carried out. The study aims at a numerical calculation of the dominant hybrid mode complex propagation constant in the CPW printed on a bianisotropic substrate. The herein considered bianisotropy is characterized by full 3×3 tensors of permittivity, permeability and magnetoelectric parameters. The study is based on the numerical derivation of the Green's functions of such a complex medium in the spectral domain. The study is carried out using the Full Generalized Exponential Matrix Technique based on matrix- shaped compact mathematical formulations. The Spectral Method of Moments (SMoM) and the Galerkin's procedure are used to solve the resulting homogeneous system of equations. The effect of the chiral and achiral bianisotropy on the complex propagation constant is particularly investigated. Goo d agreements with available data for an anisotropic-medium-based suspended CPW structure are achieved. Various cases of chiral and achiral bianisotropy have been investigated, and particularly, the effect on the dispersion characteristics is presented and compared with cases of isotropic and bianisotropic Tellegen media. / FCT/MEC through national funds and when applicable co-financed by the ERDF, under the PT2020 Partnership Agreement under the UID/EEA/50008/2019 project.

In this thesis, a cavity-backed slot antenna array is designed for relatively wide instantaneous bandwidth, high gain and low sidelobes. The array consists of four, rectangular, slot elements, arranged side-by-side in a linear array and developed around 5GHz. Two feed points, at opposing sides of the printed array, each excite two of the slot elements through a series feed. This bidirectional feed presents symmetry to the design and prevents the tendency of beam-drift versus frequency as is common with many series-fed arrays. While being fed in-phase, the array will maintain boresight at broadside over the entire operating bandwidth. Also, the additional port allows for the potential introduction of a phase offset and, therefore, beam tilt. Finally, the printed array is designed to function within a quarter-wave, metallic cavity to achieve unidirectional radiation and improve gain.

Diese Arbeit beschäftigt sich mit drei Aspekten der AdS/CFT-Korrespondenz, die alle einen Schritt über die klassische SUGRA-Näherung hinausgehen. Zuerst diskutieren wir den BMN Grenzfall der Korrespondenz und untersuchen insbesondere das Verhalten der quantenfeldtheoretischen Propagatoren. Dabei weisen wir nach, dass die Propagatoren im für den BMN Fall relevanten Hintergrund ebener Wellen semiklassisch (WKB) exakt beschrieben werden. Danach wird im Rahmen der AdS/CFT-Korrespondenz der Grenzfall verschwindender Kopplung der konformen Feldtheorie betrachtet. Zur technischen Vereinfachung geschieht dies für das Beispiel des O(N)-Vektormodells. Dabei wird die OPE der Vierpunktfunktionen so umgeschrieben, dass sie strukturelle Ähnlichkeit mit Witten-Diagrammen einer korrespondierenden Theorie von Strömen mit höherem Spin hat. Außerdem wird das O(N)- Vektormodell bei großem N am wechselwirkenden Infrarot-Fixpunkt untersucht. Im letzten Punkt wenden wir uns schließlich der ursprünglichen AdS/CFTDualität unter Mitnahme der nächstführenden Ordnung der 1/N-Entwicklung zu. Für die Deformationen der CFT durch relevante Doppelspur-Operatoren finden wir bei Zustandssummen und konformen Anomalien exakte Übereinstimmung zwischen direkter und AdS-seitiger indirekter Rechnung. Damit wird ein nicht trivialer Test der Korrespondenz über die SUGRA-Näherung hinaus erbracht. / This thesis deals with three corners of the AdS/CFT Correspondence that lie one step beyond the classical supergravity (SUGRA) approximation. We first explore the BMN limit of the duality and study, in particular, the behavior of field theoretic propagators in the corresponding Penrose limit. We unravel the semiclassical (WKB-) exactness of the propagators in the resulting plane wave background metric. Then, we address the limit of vanishing coupling of the conformal field theory (CFT) at large N. In the simplified scenario of Higher Spin/O(N) Vector Model duality, the conformal partial wave (CPW) expansion of scalar four-point functions are reorganized to make them suggestive of a bulk interpretation in term of a consistent truncated massless higher spin theory and their corresponding exchange Witten graphs. We also explore the connection to the interacting O(N) Vector Model at its infra-red fixed point, at leading large N. Finally, coming back to the gauge theory, we study the effect of a relevant double-trace deformations of the boundary CFT on the partition function and its dual bulk interpretation. We show how the one-loop computation in the Anti-de Sitter (AdS) space correctly reproduces the partition function and conformal anomaly of the boundary theory. In all, we get a clean test of the duality beyond the classical SUGRA approximation in the AdS bulk and at the corresponding next-to-leading 1/N order of the CFT at the conformal boundary.

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No. of bitstreams: 1 AlexandreHSO_DISSERT.pdf: 4241907 bytes, checksum: 7c578927aa89afb44e48b7e51e99d120 (MD5) Previous issue date: 2017-04-07 / Fundação de Apoio à Pesquisa do RN / The knitted fabrics have elastic, easy production and malleability properties, these characteristics be useful in the design of flexible antennas, that can be used in a RFID tag, for example. The mean objective of this work is development of antenna with a Coplanar Waveguide fed (CPW), in a textile knitted substrate, for use in active RFID systems in microwave frequency of 2.45 GHz. From the characterization of the electrical properties by a Vector Networks Analyzer and one with a Dielectric Probe kit, obtained the values of Electrical Permissiveness and Loss Tangent, in sequence was carried out the characterization of the textile properties of Linear Density, Basis weight, Dimensional stability and Tensile Strength, based on the data obtained in characterization process, was chosen two fabrics with properties favorable to the design, modeling and construction of antennas. After the selection of the tissues, simulations were performed on Ansys HFSStm (High Frequency Structural Simulator) to obtain the parameters of Return Loss, Radiation Diagram, Current Density, Impedance, Gain and VSWR, as well as dimensional optimization of the antennas. Two CPW-fed antennas were simulated, one on textile substrate made from Soybean Protein Fibers (SPF) and the other with Polypropylene with corn Polylactic Acid fibers (PP + PLA). Based on the simulations, two antennas with their respective textile substrates were constructed and using a vector network analyzer, the return loss and the impedance shown by the Smith Chart were measured. Both showed a return loss below -10dB for central design frequency and wide bandwidth. The simulated and measured results were compared, analyzing them according to the specialized reading in the area. Showing the feasibility of developing CPW antennas in knitted fabrics for active RFID systems, in addition to the possibility of interoperability in internet of things (IoT) communication systems / Os tecidos de malha apresentam propriedades de elasticidade, facilidade de fabricação e maleabilidade, devido a estas características a utilização desse tipo de tecido traz vantagens na fabricação de antenas para aplicação no desenvolvimento de uma tag RFID. O presente trabalho tem como objetivo desenvolver antenas com guias de ondas coplanares (CPW), em substrato têxtil em estruturas de malha, para utilização em sistemas ativos de Identificação por Rádio Frequência, RFID, para frequência de operação em micro-ondas de 2,45 GHz. Foi realizada a caracterização das propriedades elétricas por meio de um Analisador de Redes Vetoriais e com uma sonda de medição de matérias dielétricos, obtive-se então os valores de Permissividade elétrica e Tangentes de perdas, em sequência foi realizada a caracterização das propriedades têxteis de Título, Gramatura, Estabilidade Dimensional e Resistência a tração, com base nos dados obtidos no processo de caracterização se elegeu dois tecidos com propriedades favoráveis ao projeto, modelagem e construção das antenas têxteis. Após a seleção dos tecidos foram feitas simulações no Ansys HFSS® (High Frequency Strucutural Simulator) para obtenção dos parâmetros de Perda de retorno, Diagrama de radiação, Densidade de corrente, Impedância, Ganho e VSWR, além da otimização dimensional das antenas. Foram simuladas duas antenas CPW, uma em substrato têxtil feito de fibras de Proteína de Soja (SPF) e outra com fibras de Polipropileno com Ácido Polilático de Milho (PP+PLA). Com base nas simulações foram construídas duas antenas com os respectivos substratos têxteis e utilizando um analisador de redes vetoriais foram medidos a perda de retorno e a impedância, mostrada por meio da Carta de Smith. Ambas apresentaram uma perda de retorno abaixo de -10 dB para frequência central de projeto e uma alta largura de banda. Foi realizada a comparação dos resultados simulados e os efetivamente medidos, analisando-os de acordo com a literatura especializada na área. Mostrando a viabilidade do desenvolvimento de antenas CPW em tecidos de malha para sistemas RFID ativos, além da possibilidade da interoperabilidade em sistemas de comunicação por Internet das coisas, Internet of Things, IoT / 2017-07-10

The project contains adventurous research, with an aim to understand and design a planar Gunn diode with a novel integrated circuit configuration to extract the 2nd harmonic. This will potentially enhance the Gunn diode as a high frequency source towards frequencies in excess of 600 GHz. The RF performance from the above integrated circuit was achieved by design and simulation of radial and diamond stub resonators, which were used to short the fundamental oscillation frequency while allowing the second harmonic frequency to pass through to the load. The diamond stub resonator is a new configuration offering a number of advantages which include a higher loaded quality factor and occupies 55% less chip area than a comparable radial stub resonator. The designed novel circuits with integrated planar Gunn diode were fabricated using microwave monolithic integrated circuits (MMIC) technology at the James Watt Nanofabrication centre in Glasgow University. Full DC and microwave characterisation of the diodes and integrated circuits with diodes was carried out using a semiconductor analyser, network analyser (10 MHz to 110GHz) and spectrum analyser (10 MHz to 125GHz). The microwave measurements were carried out at the high frequency RF laboratories in Glasgow University. Both GaAs and InP based Gunn diodes were characterised and RF characterisation work showed that higher fundamental frequencies could be obtained from Gunn diodes fabricated on InGaAs on a lattice matched InP substrate. Planar Gunn diodes with an anode to cathode spacing of 4 microns giving a fundamental frequency of oscillation of 60 GHz were fabricated as an integrated circuit with coplanar waveguide (CPW) circuit elements to extract the second harmonic. A second harmonic frequency of 120 GHz with an RF output power of -14.11 dBm was extracted with very good fundamental frequency suppression. To the authors knowledge this was the first time second harmonic frequencies have been extracted from a planar Gunn diode technology. Aluminium gallium arsenide (AlGaAs) planar Gunn diodes were also designed with an integrated series inductor to match the diode at the fundamental frequency to obtain higher RF output powers. Devices with a 1 micron anode to cathode separation gave the highest fundamental oscillation frequency of 121 GHz the highest reported for a GaAs based Gunn diode and with an RF output power of -9 dBm. These circuits will have potential applications in secure communications, terahertz imaging etc.

Made available in DSpace on 2014-06-12T17:36:44Z (GMT). No. of bitstreams: 2 arquivo2583_1.pdf: 1542172 bytes, checksum: ea25c0c3bfa9a954147f029a13be4c79 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2009 / Companhia Hidro Elétrica do São Francisco / Os sistemas IFM (do inglês Instantaneous Frequency Measurement) são largamente usados na eletrônica para fins militares e em sistemas inteligentes para a detecção de sinais desconhecidos com velocidade e precisão ao longo de uma larga banda do espectro de frequências. Além disso, o aumento da quantidade de sistemas irradiantes faz crescer a importância de dispositivos para identificação de sinais desconhecidos. O sistema IFM monitora, de forma simultânea, todas as frequências da banda para a qual foi projetado, sem a necessidade de fazer uma varredura de espectro, detectando instantaneamente os sinais desconhecidos. Nos sistema IFM existem os circuitos discriminadores de fase. Os sinais de saída dos discriminadores de fase servem para formar um código binário que associa uma palavra binária a uma sub-banda de frequência. Neste trabalho, será demonstrado, através de equações de projeto, simulações eletromagnéticas e medições experimentais, o comportamento de interferômetros coplanares de micro-ondas atuando como discriminadores em um sistema IFM simples de 4 bits. Esse sistema é projetado para operar na banda de 5 a 6 GHz, com uma resolução de 62,5 MHz, identificando 16 sub-bandas distintas de frequência. Os interferômetros coplanares são implementados com circuitos de micro-ondas em CPS (do inglês Coplanar Strips) e CPW (do inglês Coplanar Waveguide), seus resultados experimentais são comparados aos teóricos e simulados

L'étude du contrôle optique de composants hyperfréquences consiste en la compréhension et la simulation des phénomènes physiques mis en jeu, à savoir, l'injection optique et la propagation d'une onde hyperfréquence au sein de la charge photo-induite. L'objectif est d'obtenir une simulation complète. Ainsi la partie optique est résolue par un calcul semi-analytique tridimensionnel de l'injection optique pour obtenir la concentration de porteurs excédentaires dans le substrat. Ce calcul semi-analytique permet de plus la réalisation d'une étude de sensibilité par rapport aux paramètres physiques et géométriques du substrat et du faisceau laser. Dans un deuxième temps, cette charge photo-induite, déduite de la concentration, est modélisée sous un logiciel électromagnétique pour obtenir le comportement fréquentiel du composant contrôlé optiquement. Toutes ces simulations sont enfin comparées aux mesures pratiques réalisées sur des composants simples en technologie coplanaire.

Rapid advancement in wireless communications over the years has been the driving force for many novel technologies providing compact and low cost solutions. Recent development of multilayer coplanar waveguide (CPW) MMIC technology promises realization of 3D MMIC in which large area-occupying passive components are translated from horizontal into vertical configuration resulting compact structure. The other main advantages of this technology are elimination of via-holes and wafer-thinning giving alternative performance solution, if not better, from the traditional MMIC. In this thesis, thermal and small-signal characteristics of prefabricated AlGaAs/InGaAs pseudomorphic high electron mobility transistors (pHEMTs) on semi-insulating (S.I.) GaAs substrate incorporated in the 3D MMIC technology have been analysed and modelled for the first time. A comprehensive small-signal parameter extraction procedure has been successfully developed which automatically determines the device small-signal parameters directly from the measured S-parameters. The developed procedure is unique since it provides a great deal of data on measured devices over a wide bias, temperature and frequency range for future incorporation of different active devices for the 3D MMIC technology and provides a first hand knowledge of how the multilayer structure will affect the performance of pre-fabricated pHEMTs. The extracted small-signal models of both pre- and post- multilayer processed pHEMTs have been compared and validated to the RF S-parameters measurements. The main focus was drawn upon the temperature dependent model parameters and how the underlying physics of the transistors behave in response to the change of temperature. These novel insights are especially valuable for devices designed specifically for high power applications like power amplifiers where tremendous heat could be generated. The data can also be interpreted as a way to optimise the multilayer structure, for example, alternative material with different properties can be implemented. The governing physics affecting device performance are also modelled and discussed empirically in details through extracted device parameters. These investigations would assist in the development of reliable, efficient and low cost production of future compact 3D multilayer CPW MMICs.

Slot dipole antennas fed by coplanar waveguide (CPW) on substrates consisting of a single dielectric layer exhibit various attractive qualities, including significantly wider impedance bandwidth than comparable microstrip patch antennas. For applications that call for unidirectional radiation, such as antennas on airframes, a conducting back plane is needed. A CPW on a conductor-backed single-dielectric-layer substrate will always experience power leakage into the TEM parallel-plate mode. On the other hand, it is possible to design CPW lines on conductor-backed two-layer substrates that are free from leakage into the substrate. However, once the CPW is used as feed line to a slot dipole, power leakage into the TM0 substrate mode caused by the transition between the CPW and the radiating slot, and by the radiating slot itself, may still severely compromise radiation efficiency. This study has two main contributions to offer. First, a paucity of work on CPW-fed slot antennas on conductor-backed two-layer substrates is alleviated by providing a fuller characterization of single-slot behaviour on two-layer parallel-plate substrates than is currently available, and by systematically investigating a practically feasible minimum antenna configuration, namely broadside twin slots, that is not debilitated by the problem of substrate mode leakage. Results obtained with the moment-method-based electromagnetic simulator IE3D that emphasize the trade-off between radiation efficiency and impedance bandwidth are presented; they can be used for design purposes. For instance, with respect to single slots on a substrate with an electrically thin top dielectric layer and an air bottom layer, it is shown that radiation efficiency increases and bandwidth decreases as height of the bottom substrate layer increases. For broadside twin slots, it is demonstrated that spacing close to half a wavelength of the two-layer parallel-plate TM0 mode apart can yield a large improvement in radiation efficiency over that of a single slot (a reduction in bandwidth however occurs). The second main contribution is the development of an approach for finding the mutual admittance Y12 between CPW-fed slots on conductor-backed two-layer substrates that can be more readily incorporated in an iterative array design procedure than a moment-method-based technique, yet is of comparable accuracy; it is built on a standard reciprocity-based expression. As an initial step, the mutual admittance between CPW-fed slots on a conductor-backed two-layer substrate with an air bottom layer is characterized using IE3D. This involves presenting curves for Y12 between twin slots against slot separation d along standard paths for slot half-lengths in the vicinities of the first and second resonant half-lengths of the corresponding isolated slots (such data might be used towards a first-order array design), and a study of the effect of back plane distance (i.e., bottom layer height) on mutual coupling. The bulk of the thesis however is devoted to the above reciprocity-expression approach. Simplifying assumptions are outlined that make it possible to determine Y12 against d by performing a once-only moment-method analysis of each slot in isolation, and then calculating external and internal reaction integrals at each value of d. This is significantly more economical than carrying out a full moment-method analysis of the whole twin-slot structure at every instance of d. Evaluation of the internal reaction integral requires the appropriate component of the spatial-domain Green’s function for the substrate, which is derived in a form containing Sommerfeld-type integrals; treatment of singularities is discussed. The reciprocity-expression approach is verified by comparing Y12 against d curves for twin slots and non-identical slot pairs on a variety of conductor-backed two-layer substrates to IE3D simulations. A procedure that involves judicious selection of reference planes is introduced by which agreement between the methods for the special case of twin slots with the same half-length as the corresponding isolated second-resonant slot can be even further improved. A measurement is provided that validate theoretical calculations. / Thesis (PhD)--University of Pretoria, 2008. / Electrical, Electronic and Computer Engineering / unrestricted

Well-known dielectric image guide reach in millimeter-wave interesting results. Compared to a conventional types of lines and waveguides is characterised by low-through loss for frequencies approaching 100 GHz. This work is detail focused to basic characteristics and especially type of perforate highpermitivity substrate for obtain implemented waveguide to dielectric board (SIIG). The work also contains couple suggestions for various transitions from a commonly used lines and waveguides. Simulation results using finite element method is achieved attenuation values below 2 dB, which corresponds to a 2 cm length and include a waveguide itself with a pair of transitions. Finally, this work also designed the production method and SIIG applicatoin in practicle.