Yes / A Novel design of a curved single-layered frequency selective surface with an 11 × 11 array of a 13 × 13 mm-sized unit cell has been merged with a miniaturized, CPW-fed ultra-wideband monopole of dimensions (20 × 25 mm2) for gain enhancement. The suggested prototype, crafted on an FR-4 dielectric substrate and demonstrates a very broad bandwidth starting from 2.66 to 17.98 GHz (148%), which covers the entire UWB frequency band. The combined antenna-curved FSS reflector shows a very important gain improvement from 0.2–5.4 dB to 8.8–14.9 dB, having a peak gain increase of 10 dB at 10.6 GHz. Basic design features were studied and discussed through simulations, yielding promising results The proposed structure can be used in UWB and GPR applications. / The full-text of this article will be released for public view at the end of the publisher embargo on 31 Oct 2024.

There has been increased interest in exploring high frequency (mm-wave) spectrum (particularly the 30 and 60 GHz ranges), and utilizing silicon-based technology for reduced-cost monolithic millimeter integrated circuits (MMIC), for applications such as WLAN, inter-vehicle communication (IVC) automotive radar and local multipoint distribution system (LMDS). Although there has been a significant increase in silicon-based implementations recently, this area still has significant need for research and development. For example, one microwave/mm-wave front-end component that has seen little development in silicon is the power amplifier (PA). Two potential technologies exist for providing a solution for low-cost microwave/mm-wave power amplifiers: 1) Silicon-Germanium (SiGe) HBT and 2) Complementary metal-oxide semiconductor (CMOS). SiGe HBT has become a viable candidate for PA development since it exhibits higher gain and higher breakdown voltage limits compared to CMOS, while remaining compatible with BiCMOS technology. Also, SiGe is potentially lower in cost compared to other compound semiconductor technologies that are currently used in power amplifier design. Hence, this research focuses on design of millimeter-wave power amplifiers in SiGe HBT technology. The work presented in this thesis will focus on design of different power amplifiers for millimeter-wave operating frequencies. Amplifiers present the fundamental trade-off between linearity and efficiency. Applications at frequencies highlighted above tend to be point-to-point, and hence high linearity is required at the cost of lowered efficiency for these power amplifiers. The designed power amplifiers are fully differential topologies based on finite ground coplanar waveguide (FGC) transmission line technology, and have on-chip matching networks and bias circuits. The selection and design of FGC lines is supported through full-wave EM simulations. Tuned single stub matching networks are realized using FGC technology and utilized for input and output matching networks. Two 30-GHz range SiGe HBT PA designs were carried out in Atmel SiGe2RF and IBM BiCMOS 8HP IC technologies. The designs were characterized first by simulations. The performance of the Atmel PA design was characterized using microwave/mm-wave on wafer test measurement setup. The IBM 8HP design is awaiting fabrication. The measured results indicated high linearity, targeted output power range, and expected efficiency performance were achieved. This validates the selection of SiGe HBT as the technology of choice of high frequency point-to-point applications. The results show that it is possible to design power amplifiers that can effectively work at millimeter-wave frequencies at lower cost for applications such as mm-wave WLAN and IVC where linearity is important and required transmitted power is much lower than in cellular handset power amplifiers. Moreover, recommendations are made for future research steps to improve upon the presented designs. / Master of Science

In this modern age of information, the demands on data transmission networks for greater capacity, and mobile accessibility are increasing drastically. The increasing demand for mobile access is evidenced by the proliferation of wireless systems such as mobile phone networks and wireless local area networks (WLANs). The frequency range over which an oxygen resonance occurs in the atmosphere (~58-62 GHz) has received recent attention as a possible candidate for secure high-speed wireless data networks with a potentially high degree of frequency reuse. A significant challenge in implementing data networks at 60 GHz is the manufacture of low-cost RF transceivers capable of satisfying the system requirements. In order to produce transceivers that meet the additional demands of high-volume, mobility, and compactness, monolithic millimeter wave integrated circuits (MMICs) offer the most practical solution. In the design of radio tranceivers with a high degree of integration, the receiver front-end is typically the most critical component to overall system performance. High-performance low-noise amplifiers (LNAs) are now realizable at frequencies in excess of 100 GHz, and a wide variety of mixer topologies are available that are capable of downconversion from 60 GHz. However, local oscillators (LOs) capable of providing adequate output power at mm-wave frequencies remain bulky and expensive. There are several techniques that allow the use of a lower frequency microwave LO to achieve the same RF downconversion. One of these is to employ a subharmonic mixer. In this case, a lower frequency LO is applied and the RF mixes with a harmonic multiple of the LO signal to produce the desired intermediate frequency (IF). The work presented in this thesis will focus on the development of a GaAs MMIC 4-X subharmonic mixer in Finite Ground Coplanar (FGC) technology for operation at 60 GHz. The mixer topology is based on an antiparallel Schottky diode pair. A discussion of the mechanisms behind the operation of this circuit and the methods of practical implementation is presented. The FGC transmission lines and passive tuning structures used in mixer implementation are characterized with full-wave electromagnetic simulation software and 2-port vector network analyzer measurements. A characterization of mixer performance is obtained through simulations and measurement. The viability of this circuit as an alternative to other high-frequency downconversion schemes is discussed. The performance of the actual fabricated MMIC is presented and compared to currently available 60 GHz mixers. One particular MMIC design exhibits an 11.3 dB conversion loss at an RF of 58.5 GHz, an LO frequency of 14.0 GHz, and an IF of 2.5 GHz. This represents excellent performance for a 4X Schottky diode mixer at these frequencies. Finally, recommendations toward future research directions in this area are made. / Master of Science

The designs of various feeding networks for microstrip antennas have been investigated in this dissertation. In the active microstrip antenna designs, an amplifier-type microstrip antenna integrates a two- port amplifier circuitry to the various passive antennas through a 50£[ inset microstrip feed line which can function in broadband operation¡ACP operation and dual-frequency operation. As for the broadband circularly polarized microstrip antenna with a dual-perpendicular feed design, antenna with a dual-perpendicular feed which was formed by a Wilkinson power divider with a quarter-wavelength section of microstrip line for providing equal splitting of the input power and 90¢X phase difference to the two feed points has been presented. The broadband CP bandwidth can be achieved due to the good isolation between the two output lines of the feed network. In the microstrip antennas with CPW feed designs, we first proposed a microstrip antenna with three-dimensional CPW feed. A separate feed substrate is used which can provide a large-area space for the layout of complicated microwave circuitry. In addition, the feed substrate can also be oriented to the patch substrate with various angles, resulting in more flexibility in the proposed three-dimensional feed design. Finally, we proposed a design with two slot lines located at both sides of the coupling slot which can lengthen the excited patch surface current path, thus the resonant frequency is reduced and an antenna size reduction up to 40% has been obtained.

This thesis presents the rectifying antenna potential for infrared and millimeter wave energy conversion. Infrared imaging is one of the emerging technologies that have attracted considerable attention in the next generation of military, medical, and commercial applications. Moreover, with the ever-increasing congestion of the electromagnetic spectrum at RF and microwave frequencies and the establishment of firm civilian and military requirements best met by millimeter wave systems, the interest in the technology has grown and is now firmly established. During this work a 2.5GHz slot antenna, a 2.5GHz Schottky diode detector, a CPW-to-Microstrip transition, a fully integrated Rectenna element, and a 94GHz slot antenna were designed, fabricated, and tested. Results on the performance of the devices show a great deal of correlation between the simulated and measured data. To perform an initial study, the CPW-fed narrow slot antenna is designed at 2.5GHz and implemented on an FR-4 board. This investigation serves as the basis for the development of the Rectenna element at millimeter wave frequencies. In order to increase the bandwidth of the slot antenna, a 2.5GHz CPW-fed wide slot antenna with U-shaped tuning stub is realized, which provides a 60% increase in bandwidth while keeping the same radiation characteristics. In addition, a set of simulations is performed to show how a reflector plate affects the radiating properties of the slot antenna. A 2.5GHz square-law detector is also designed, fabricated, and tested in order to rectify the RF signal delivered by the antenna. The fabricated detector presents a well matched condition at the design frequency with a dynamic range found to be from --17dBm to --50dBm. The low frequency Rectenna element prototype is then integrated within a single FR-4 board. This is accomplished by implementing a compact via-less CPW-to-Microstrip transition. Finally, a 94GHz CPW-fed wide slot antenna is realized on a 10μm high resistivity silicon membrane. This antenna shows a great deal of similarity to the 2.5GHz slot antenna. This low profile antenna presents at least a 10dB return loss over the entire W band frequency window. Simulated antenna efficiencies of up to 99% were achieved assuming a perfect conductor.

Orientador: Luiz Carlos Kretly / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-13T08:18:49Z (GMT). No. of bitstreams: 1 Atanazio_PauloFilipeBraghetto_M.pdf: 6727187 bytes, checksum: 90bbbbf904ffcce6757eeaeefe4abd96 (MD5) Previous issue date: 2009 / Resumo: O propósito deste trabalho é, a partir dos conceitos de linhas de transmissão, teoria de filtros e o conhecimento pioneiro deste grupo acerca das chaves MEMS de RF, propor duas aplicações reais baseadas nesta estrutura singular: um deslocador de fase e um filtro sintonizável na faixa de 0,1-35GHz e banda Ku (12,4-18GHz) respectivamente. Uma abordagem puramente eletromecânica é realizada na etapa inicial, observando a tensão de ativação da chave para diferentes formas estruturais, desmistificando a histerese mecânica, fenômeno intrínseco a este tipo de dispositivo. Na segunda fase do trabalho é feito um detalhamento do comportamento eletromagnético da chave MEMS, explorando fortemente a extração dos parâmetros elétricos e sua inserção em outros circuitos. Por fim, a implementação do filtro sintonizável e do deslocador de fase realizouse baseada nos conceitos de DMTL - Distributed MEMS Trasmission Lines - onde tanto a seleção da frequência central de passagem do filtro, quanto o comprimento elétrico total do deslocador são controladas pela capacitância variável da chave MEMS, de acordo com uma tensão de controle DC aplicada. / Abstract: The purpose of this work is, based on transmission line concepts, filter theory and the pioneer knowledge of this group about RF MEMS Switches, propose two physical applications employing this singular structure: a phase shifter and a tunable filter at 0.1 - 35GHz range and Ku band respectively. A purely electromechanical approach is done at the initial step, observing the switch pull-in voltages for several structural geometries, demystifying the mechanical hysteresis, intrinsic phenomena of this kind of device. On the second phase of the work, the MEMS switch electromagnetic behavior is detailed, strongly exploring the electrical parameters extraction and its application on other types of circuits. Finally, the tunable filter and phase shifter are implemented through DMTL - Distributed MEMS Transmission Lines - concepts, where frequency selection and the amount of phase shifting are controlled by the variable switch capacitance according to the applied DC control voltage. / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

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Diploma thesis is focused to design of a system with circularly polarized wave for frequency band 2.4 GHz. The thesis introduces question of the microwave antennas, matching circuits and circular polarization circuit. It also includes a design of a circuit for available chip antenna (2450AT45A100) measurement and its measuring with connected chip antenna. Design and measurement of a circular polarization circuit using available chip antennas are also included in this thesis.

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