Yes / A type of telecommunication technology called an ultra-wideband (UWB) is used to provide a typical solution for short-range wireless communication due to large bandwidth and low power consumption in transmission and reception. Printed monopole antennas are considered as a preferred platform for implementing this technology because of its alluring characteristics such as light weight, low cost, ease of fabrication, integration capability with other systems, etc. Therefore, a compact-sized ultra-wideband (UWB) printed monopole antenna with improved gain and efficiency is presented in this article. Computer simulation technology microwave studio (CSTMWS) software is used to build and analyze the proposed antenna design technique. This broadband printed monopole antenna contains a jug-shaped radiator fed by a coplanar waveguide (CPW) technique. The designed UWB antenna is fabricated on a low-cost FR-4 substrate with relative permittivity of 4.3, loss tangent of 0.025, and a standard height of 1.6 mm, sized at 25 mm × 22 mm × 1.6 mm, suitable for wireless communication system. The designed UWB antenna works with maximum gain (peak gain of 4.1 dB) across the whole UWB spectrum of 3–11 GHz. The results are simulated, measured, and debated in detail. Different parametric studies based on numerical simulations are involved to arrive at the optimal design through monitoring the effects of adding cuts on the performance of the proposed antennas. Therefore, these parametric studies are optimized to achieve maximum antenna bandwidth with relatively best gain. The proposed patch antenna shape is like a jug with a handle that offers greater bandwidth, good gain, higher efficiency, and compact size.

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

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.

The desire to counter multipath effects and improve communication links between mobile wireless systems in dense environment has led to much research in implementing antenna diversity. Space diversity, utilizing two or more antennas separated several wavelengths from one another, is one of the most popular method to achieve this operation. Meanwhile, polarization diversity, utilizing two orthogonal polarizations, has become more attractive in reducing cost and size of antenna systems. Polarization diversity is achieved using two orthogonal feeds to excite the two orthogonal polarization planes of the antenna. The challenge associated with designing dual polarized antennas is the need to reduce isolation between the feed and cross polarization level while maintaining a high efficiency. While a number of studies are successful in realizing polarization diversity, their antenna structure typically present more complex structures involving multiple layers. This thesis presents a novel method to implement polarization diversity on a miniature antenna using a simple planar structure. The antenna structure uses two crossed slots further miniaturized using a method derived from a recent study on miniaturized spiral slot antenna. At an operating frequency of ~ 1 GHz, the antenna is capable of achieving efficiency greater than 90% with a size as small as 0.08 .? x 0.08? The dual polarization operation is achieved by exciting the magnetic currents of the crossed slots with two orthogonal coplanar waveguide feeds. Simulation results of the proposed antenna yield an isolation > 15 dB with cross polarization levels > 10 dB. Theantenna structure was designed using CST Microwave Studio and the simulations were performed using IE3D simulation software.

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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