Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 70-72). Also available in electronic version.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves [74]-76). Also available in electronic version.

Thesis (M.S.) -- Worcester Polytechnic Institute. / Keywords: RSS localization; WiFi localization; WIFI RFID; Performance Evaluation Testbed; Channel modeling. Includes bibliographical references (leaves 100-102).

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 67-72). Also available in electronic version.

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2016. / In all radio frequency (RF) electronic communication systems, power amplifiers (PAs) are used to generate the final transmitted signal. Specifically, these PAs are used to increase the output power of the transmitted signal. The PA accomplishes this by converting the applied direct current (DC) power to the PA into RF power, while being driven by a RF input signal. The portion of DC power that is not converted into RF power is dissipated as heat. The power conversion mechanism that takes place in a PA is described by the power conversion efficiency (PE) and the power added efficiency (PAE). A CubeSat is a small satellite in the shape of a 10 × 10 × 10 cm cube, weighing less than 1 kg and contains a RF electronic communication system which allows communication with the satellite. A CubeSat requires a PA with high PE in order to increase the lifetime of the on-board battery, facilitate thermal management on-board the satellite, increase system reliability, and reduce the size and manufacturing cost of the satellite. To maximize the theoretical PE of a RF PA, several design techniques and classes of operation were investigated, the basis of which lies in the fulfilment of the necessary and sufficient conditions for a maximum PE. A PA, which uses the Class-F-1 (inverse Class-F) mode of operation, fulfils the necessary and sufficient conditions for a maximum theoretical PE, and therefore presents itself as a good option for a high efficiency PA. This thesis presents the design of a Class-F-1 PA, using the Cree CGH40010F GaN power active device. An optimum output matching network is used to terminate the drain of the GaN power active device with the required load impedances at the fundamental, 2nd and 3rd harmonic frequencies of operation. The designed PA delivers a maximum PE of 95 % at an operating frequency of 2.2 GHz, a maximum PAE of 82 % at an operating frequency of 2.2 GHz and a maximum output power of 40.6 dBm at an operating frequency of 2.2 GHz.

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2017. / RF and microwave filters can be implemented using ceramic coaxial resonators. This technology has been widely employed in nanosatellite communications systems recently, owing to its large quality factor (Q), permitting them to have low loss and narrow bandwidth. Features such as high selectivity, high power handling, excellent rejection, and low passband insertion loss are just a few of the key performance areas offered by ceramic coaxial resonators. This feature makes them suitable for use in bandpass filters. Applications with demanding specifications requiring low volume and mass make use of this technology. Fulfilling the required performance goals can be challenging, given the size and weight restriction. Difficulties such as finding the correct length of resonators and the coupling capacitors’ structure to meet the size restriction, limit the type of ceramic coaxial resonators to use. This thesis presents the design of a bandpass filter using ceramic coaxial resonators, which provides evidence of the concept for F’SATI’s future needs. This design will be used in an imminent space mission and the intention is to mount the bandpass filter in the receiver communications system. An intensive investigation was conducted into the use of filters for nanosatellite communication systems. The Chebyshev LC ladder low pass prototype was used to derive the conventional bandpass filter. Thereafter, the coupled resonator bandpass filter was derived using the conventional bandpass filter topology combined with the admittance inverter. Following this, using the ceramic coaxial resonators datasheet and information provided by the manufacturers, the coupled resonator bandpass filter was converted into a 3D model for further simulations, using CST Microwave Studio®. The ceramic coaxial resonator filter fabricated using Rogers’s material provided satisfactory results at its operating frequency between 2.2 GHz and 2.3 GHz. A radiation level test was performed on the filter to justify the use of the metallic enclosure. The test presented a low level of radiation measured at the filter operating frequency (2.25 GHz). The filter was also subjected to temperature cycling. / French–South African Institute of Technology (F’SATI) National Research Foundation (NRF)

Orientador: Antonio Batocchio / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-16T21:18:07Z (GMT). No. of bitstreams: 1 Silva_SamuelBlochda_M.pdf: 9873056 bytes, checksum: ae2411c7a4bad4e10affd179ddc9a346 (MD5) Previous issue date: 2010 / Resumo: Entende-se com base nos resultados das pesquisas do Auto-ID Center, que a tecnologia de RFID poderá fomentar a criação de uma "nova superfície de contato" entre as unidades de negócios, melhorando muito a qualidade da informação nas cadeias de suprimentos aeronáuticos. Neste contexto a tecnologia forneceria condições "ideais" à automação de várias atividades de apontamentos manuais comumente existentes aos processos internos e externos das empresas envolvidas. Esta melhora no fluxo da informação precisa chegar ao nível dos componentes aeronáuticos, uma vez que os mesmos estão sujeitos a diferentes estados e condições de operação e manuseio (temperatura, unidade, vibrações). De alguma maneira estes itens precisam ser controlados e rastreados em função das várias necessidades industriais e de legislação. Outro ponto importante é a crescente preocupação dos fabricantes aeronáuticos em relação ao "pedigree eletrônico" de seus componentes. Não obstante a isto, produzir somente nas quantidades solicitadas e nas datas sincronizadas pela linha de montagem do avião, é uma das mudanças mais importantes no contexto do fluxo de valor dos fabricantes aeronáuticos. Ou seja, sincronizar os componentes conforme a demanda é resultado direto de um modelo robusto de fornecimento, baseado na confiança "cliente-fornecedor" sem a necessidade de formação de estoque. A proposta deste trabalho é apresentar os benefícios obtidos com a aplicação da tecnologia de RFID na rastreabilidade e sincronização da cadeia de suprimentos aeronáuticos, considerandose os pressupostos anteriores. / Abstract: It is understood based on the research findings of Auto-ID Center, RFID technology that could encourage the creation of a "new contact surface" between business units, improving the information quality of aeronautical supply chain. In this context the technology would provide "ideal" conditions to automation activities commonly existing manual date the internal and external processes of the companies involved. This improved flow of information needs to reach the level of aircraft components, since they are subject to different states and conditions of operation and handling (temperature, unity, vibrations). Somehow these items must be tracked and traced to the different needs and industrial legislation. Another important concern is adding aircraft manufacturers in relation to "electronic pedigree". Despite this, producing only the amount requested and the dates for the synchronized assembly line of the aircraft, is one of the most important changes in the context of the value stream of aircraft manufacturers. In other words, synchronize the components based on demand is a direct result of a robust model of delivery, based on trust "client-supplier" without building inventory. The purpose of this study is to present the benefits of the application RFID technology to tracking and synchronization of aeronautical supply chain. / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

M.Ing. / In power electronics most applications are custom designed. Even though similar topologies are used, each application is designed to fit specific requirements. Presently there is a move towards standard modules that can be connected together to perform the desired power conversion, in much the same way as IC’s have been used for a few decades now. It is important to ensure that the modules can work together without performance degradation. The close proximity of active, passive and logic devices in high power applications dramatically increases the risk of EMI between the various components. This document describes the design and characterisation of a planar conducted RF-EMI power line filter to be used between modules and between modules and power supplies. The filter consists of two sets of transmission lines in parallel. The first is a high permittivity material with nickel conductors, referred to as the attenuator. The second is a set of copper conductors that are placed on the outside of the attenuator. The filter must be able to remove conducted differential mode noise from power line to the module and from the module tot the power line. The filter dimensions are comparable to the wavelengths that have to be attenuated. This allows for a possible combination of RF filtering techniques and power line filtering techniques. The design of the filter and the electromagnetic effects that govern its behaviour is explained. The transfer characteristic of the filter is made possible by the choice of materials and their relation to each other. Each material is discussed and evaluated. Characterisation methods are described and results presented. The influence the materials have on the performance of the filter and the methods and problems of construction of the filter are discussed. The construction of the filter and the commercial processes available are discussed. A prototype filter was built to demonstrate the feasibility of the construction processes. The performance of the prototype filter was then measured. The various test set-ups for different applications are explained. Small signal tests in 50 W systems were used to allow for comparisons with other filter types. The prototype has minimal insertion loss in the pass band and an average slope of attenuation of 40 dB/decade beyond the corner frequency. The corner frequency is at 1 MHz. Transmission line theory is used to develop a distributed element model for the filter using the ABCD-matrix representation of transmission lines. From this matrix an equivalent P-model can be calculated. Applicable assumptions are made to simplify the equations and values for a lumped element P-model is calculated. Both models indicate the importance that the material parameters have on the performance of the simulation results. Good correlation between the measured performance and simulated performance is established. The material parameters are sensitive to temperature. A one-dimensional thermal model is presented to estimate the operating temperature of the filter. It is determined that the attenuation of the filter is primarily determined by the attenuator. Based on the findings, new attenuator designs are made in an attempt to improve the performance of the filter. The small signal measurements of the various designs and the test results under load conditions are compared. A power test is performed. The filter performance varies as the voltage rating is increased. Finally, a temperature characterisation is done. The filter is absorptive and heat is dissipated in both the conductors and the dielectric material. The filter performance is sensitive to the operating temperature. A summary of the technology and the evaluation of this type of filter are presented in the conclusion.

Radio Frequency IDentification (RFID) is a wireless communications technology which allows companies to secure their assets and increase the portability of information. This research was motivated by the increased commercial use of RFID technology. Existing security protocols with high levels of security have high computation requirements, and less intensive protocols can allow a tag to be tracked. The techniques proposed in this thesis result in the increase of ciphertexts available without a significant increase in processing power or storage requirements. The addition of random inputs to the generation of ciphertexts will increase the number of possible results without requiring a more advanced encryption algorithm or an increased number of stored encryption keys. Four methods of altering the plaintext/ciphertext pair (random block, set pattern, random pattern, and indexed placement) are analyzed to determine the effectiveness of each method. The number of ciphertexts generated, generation time, and generation errors were recorded to determine which of the four proposed methods would be the most beneficial in a RFID system. The comparison of these method characteristics determined that the set pattern placement method provided the best solution. The thesis also discusses how RFID transmissions appear to attackers and explains how the random inputs reduce effectiveness of current system attacks. In addition to improving the anonymity of RFID tag transmissions, the concept of authenticating random inputs is also introduced in this thesis. These methods help prevent an adversary from easily associating a tag with its transmissions, thus increasing the security of the RFID system.

Power amplifiers (PA) are typically the most power-consuming building blocks of RF transceivers. Therefore, the design of a high-efficiency radio frequency power amplifier is the most obvious solution to overcoming the battery lifetime limitation in the portable communication systems. A power amplifier's classes (A, AB, B, C, F, E, etc), and design techniques (Load-pull and large-signal S-parameters techniques) are presented. The design accuracy of class-A power amplifier based on the small-signal S-parameters was investigated, where compression in the power gain was used as an indicator for design accuracy. The effect of drain voltage variation on the power gain compression has been studied in this research. The class-E amplifier has a maximum theoretical efficiency of 100%. It consists of a single transistor that is driven as a switch and a passive load network. The passive load network is designed to minimize drain (collector) voltage and current waveforms overlapping, which minimize the output power dissipation. Two L-band class-E amplifiers are implemented in section 5.3. One of them is a lumped elements based circuit and the other is a transmission lines based circuit. Both circuits show good performance (60% PAD) over a wide bandwidth (1.0 GHz). In section 5.4, lumped elements and transmission lines based X-band class-E amplifiers are presented. Both circuits show good performance (62% PAD) over wide bandwidth (4.8 GHz). A new technique to improve the drain efficiency of the class-E amplifier has been proposed. This technique uses two passive networks. One of them is in a series with the shunt capacitor CS and the other is in a series with the transistor's source terminal. This technique shows improvement in the drain efficiency, which jumps from 62% to 82%. Last few years have seen an increase in the popularity of the wireless communication systems. As a result, the demand for compact, low-cost, and low power portable (Single-chip) transceivers has increased dramatically. Among the transceiver's building blocks is the power amplifier. Thus, there is a need for a low-cost power amplifier. A 900 MHz CMOS RF PA with one-watt output power and a high power added efficiency (68%) is presented in chapter 6. This PA can be used in the European standard for mobile communications (GSM) handset transmitter. / Ph. D.