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This study presents a planar inverted-F antenna for penta-band operation in portable devices, in accordance with the following wireless communication standards: global system for mobile communications, digital cellular system, personal communications service, universal mobile telecommunications system, and wireless local area network. The proposed antenna consists of a folded planar radiator with two slots – a J-shaped and a rectangular one – suspended above a substrate partially covered with a ground plane, to which a printed radiating strip is connected. Multiple resonances excited in this structure generate the radiation bands of the antenna, covering all required frequency ranges. A parametric analysis is conducted with the aid of electromagnetic simulation in order to evaluate the influence of geometrical dimensions of the antenna on its performance. The fabricated antenna prototype exhibits overall dimensions of 45 mm × 90 mm × 6.6 mm, and the experimental 10 dB return-loss bands of the antenna are 869–966, 1653–2200, and 2390–2505 MHz, with a measured linearly polarised gain of 2.2 dB at 915 MHz, 2.0 dB at 1900 MHz, and 1.0 dB at 2450 MHz, on the principal cut planes. A good agreement is observed between simulated and experimental results.

A loop-based excitation scheme for dielectric resonator antennas is presented. The proposed structure consists of a loop-shaped probe terminated in a short circuit. In this feeding technique, the magnetic field induced by the current loop excites the radiator of the antenna by means of electromagnetic coupling. The loop-coupling method is advantageous for the excitation of the $\text{TM}_{01\delta }$ mode in cylindrical dielectric resonator antennas since it does not require drilling the dielectric resonator, is suitable for antennas with radiator on a ground plane, and works for a variety of dielectric constants and aspect ratios for the dielectric resonator. The close agreement between measured and simulated results validates this feeding mechanism experimentally.

This paper presents a novel printed monopole antenna for quad-band operation in four WLAN bands: ISM 2.4 GHz, 5.2 GHz, 5.6 GHz, and ISM 5.8 GHz. This antenna is compact, thin, lightweight, easy to manufacture, and suitable for portable devices. It is composed of a folded strip radiator and two parasitic strips printed on a partially grounded substrate. The folded strip radiator interacts with the parasitic strips, which are connected to the ground plane, in such a way as to produce the resonant modes that originate the radiation bands of the antenna. An additional open-ended strip connected to the radiator is used to adjust the antenna input impedance in the upper operation band. A parametric study on several geometrical dimensions of the antenna is carried out in order to analyze their influence on the antenna performance. The fabricated prototype of the proposed printed monopole antenna has overall dimensions of 22 × 48 × 1.6 mm3, and the measured 10-dB return-loss bands exhibited by the antenna are 2149-2660 MHz and 5120-6035 MHz.

Water is the most valuable natural resource. To preserve this good, several water monitoring systems for pipe networks have been proposed. However, there is a lack of research on the development of high-frequency electromagnetic sensors for this task. This study proposes a non-destructive technique to locate carrying water polyvinyl chloride pipes using a microstrip patch antenna. An experimental apparatus was mounted and the resonant frequency and Q factor of the antenna were measured for different relative positions between the sensor and the pipe filled with water. To detect the pipe position, experimental data were trained and tested by applying an approach based on support vector machines. The best results were from using a simple linear kernel, which allowed 100% accuracy using a 30% fraction of data used for holdout validation.

This letter presents the design methodology of a textile rectangular patch antenna with increased bandwidth. The broadening of the antenna operating band is obtained by using a proximity coupling feed line cascaded to a quarter-wave impedance transformer. The design parameters used to enhance the antenna bandwidth are the widths of the feed line and impedance transformer. The proposed design procedure has been applied to the design of four antennas centered at 2.45 GHz using denim substrate and conductive fabric. All antennas have the same patch dimensions, but they were designed using different values for the widths of the feed line and impedance transformer. The measured 10-dB return loss bandwidth of the antenna prototypes are 11.2%, 13.4%, 17.0%, and 24.0%, in good agreement with simulated results. The effect of human body proximity and antenna curvature on the performance of the designed antennas has also been analyzed. The antenna configuration investigated has demonstrated to be able to increase the antenna operating band. The proposed design procedure is flexible, allowing the design of antennas with a variety of bandwidth values. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1906–1912, 2016

This paper proposes a new feeding scheme for exciting a higher-order resonant mode in cylindrical dielectric resonator antennas. The proposed feeding structure comprises a nonresonant microstrip patch connected to a narrow microstrip line by means of an inset. Both the microstrip patch and line are located under the antenna radiating element (dielectric resonator). A parametric analysis of this feeding structure has been carried out using electromagnetic simulation. The results of this analysis indicate that the antenna impedance matching can be adjusted by changing the length of the inset, and that different values of directivity and impedance bandwidth can be obtained by using different microstrip patch sizes and inset lengths. An antenna prototype has been designed and fabricated to validate the proposed feeding structure using a dielectric resonator with a high dielectric constant. The measured resonance frequency and impedance bandwidth of this prototype are 6.20 GHz and 25.0 MHz (fractional bandwidth of 0.403%), respectively, showing good agreement between simulated and experimental results.

In this article, a novel mobile handset planar inverted-F antenna (PIFA) for tri-band operation in GSM, DCS, and PCS bands is presented. This PIFA comprises a rectangular folded planar radiator, which has a J-shaped slot, suspended above a partially grounded substrate. In this antenna, two resonant modes are excited and originate a lower band for GSM and an upper band for DCS and PCS. The influence of several geometrical parameters of the antenna on its performance was investigated to achieve an optimal design. The fabricated prototype of the proposed PIFA has overall dimensions of 45 × 90 × 6.6 mm3. The measured 10 dB return loss bands of the antenna are 880–892 MHz and 1658–2079 MHz. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:821–825, 2013; View this article online at wileyonlinelibrary.com. DOI: 10.1002/mop.27441

This paper presents a simple equivalent electrical circuit model to represent spiral and cross inductors on CMOS Technology. The inductors were designed and simulated using Momentum/ADS from Keysight, and were fabricated on AMS 0.35 µm CMOS technology. Simulation data was used to develop a RLC model for the inductors, where the reactive elements are constant and the resistance depends on frequency. A linear equation was proposed to represent the frequency dependence of the inductor's resistance. The simulated results of spiral and cross inductors were in good agreement with the model results. On chip measurements of the inductors were performed from 1 to 10 GHz using a network analyzer. The inductance and maximum quality factor obtained from the measured data were well predicted by the proposed model, which showed good precision on spite of its simplicity.

A new methodology for the synthesis of tunable patch filters is presented. The methodology helps the designer to perform a theoretical analysis of the filter through a coupling matrix that includes the effect of the tuning elements used to tune the filter. This general methodology accounts for any tuning parameter desired and was applied to the design of a tunable dual-mode patch filter with independent control of center frequency and bandwidth (BW). The bandpass filter uses a single triangular resonator with two etched slots that split the fundamental degenerate modes and form the filter passband. Varactor diodes assembled across the slots are used to vary the frequency of each degenerate fundamental mode independently, which is feasible due to the nature of the coupling scheme of the filter. The varactor diode model used in simulations, their assembling, the dc bias configuration, and measured results are presented. The theory results are compared to the simulations and to measurements showing a very good agreement and validating the proposed methodology. The fabricated filter presents an elliptic response with 20% of center frequency tuning range around 3.2 GHz and a fractional BW variation from 4% to 12% with low insertion loss and high power handling with a 1-dB compression point higher than .

This paper presents an analysis of a reconfigurable patch filter based on a triple-mode circular patch resonator with four radial slots. The analysis has been carried out thanks to the development of a new theoretical approach of the tunable patch filter based on the coupling matrix. The coefficients of the coupling matrix related to the tunable behavior have been identified and some rules for their evolution have been derived. For a proof-of-concept, a bandpass filter has been designed with a continuous tunability obtained with varactors connected across the slots. State-of-the-art results have been obtained, with a frequency tuning range of 27% from 1.95 to 2.43 GHz and a change in fractional bandwidth from 8.5% to 31.5% for the respective frequencies. In the entire tuning range, the return loss is better than 10 dB and the maximum insertion loss is 2 dB. Due to the newly developed coupling matrix, measurements, simulations, and theory showed great agreement.

This article presents a miniaturized dual-mode narrow bandpass filter using an equilateral triangular patch resonator with an inverted T-shaped slot, which exhibited a size reduction of 37% compared with a single-mode equilateral triangular patch at the same frequency. Two- and four-pole dual-mode bandpass filters were designed and fabricated with this new resonator. Experimental results with the two-pole filter centred at 7.76 GHz showed a fractional bandwidth of 4.5%, return loss better than 17.8 dB, and minimum insertion loss of 2.2 dB. The results of the four-pole filter showed a fractional bandwidth of 3.5%, return loss better than 16 dB, minimum insertion loss of 2.6 dB, and a good second harmonic band rejection. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2897–2902, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22927

This paper presents a fully integrated BPSK (Binary Phase Shift Keying) Transmitter Front End for Ultra-Wideband (UWB) applications, designed in 130 nm CMOS technology. A simple architecture based on parallel pulse generator blocks in parallel is proposed to produce 9th derivative Gaussian pulses. In addition to the pulse generator, the circuit comprises a passive balun circuit, a common source amplifier, and a BPSK modulator. The transmitter has been simulated and the results demonstrated the circuit capability to operate as a front end BPSK transmitter. The proposed circuit generates output pulse envelopes of width 0.8 ns and maximum amplitude of 40 mVpp, an average power consumption of 1.9 uW/pulse and energy of 1.6 fJ/pulse when fed with a 715 MHz clock and 100 MHz data sources. The whole circuit occupies 480 × 320 um2 (without pads). This pulse generator complies with FCC UWB spectral power mask.)

This paper presents a textile patch antenna designed for WBAN applications at 2.45 GHz ISM band. The antenna uses denim as substrate and conductive fabric for the ground plane and radiator layers. The main purpose of this paper is to analyze the influence of typical deviation of denim properties and patch radiator dimensions on the performance of the antenna. The parameters considered in the analysis are the relative permittivity and thickness of denim and the width and length of the rectangular patch radiator. The dependence of the central operation frequency of the antenna on those parameters was studied using the antenna reflection coefficient obtained from EM simulations. Rules of thumb for one-shot design were derived and applied to design a rectangular patch antenna. An antenna prototype was fabricated and measured, demonstrating a 10 dB impedance band of 4.8 % centered at 2.45 GHz, in good agreement with simulated results.

This paper presents a miniaturized tunable bandpass patch filter using varactors. The filter is conceived with a triple-mode circular patch resonator with four slots, where the varactors were connected. The extracted equivalent model, the varactors assembly configuration and their biasing are presented. A DC bias from 0 to 20 V was applied to vary the filter's center frequency from 2.35 GHz to 1.8 GHz and its 3-dB fractional bandwidth from 31.5% to 8.5%. Within these variations, all measurements showed insertion loss lower than 2 dB and return loss better than 10 dB over the passband, ensuring a good quality factor.

This paper presents a linear analysis of the reverse feedback distributed oscillator, which is a wideband voltage controlled oscillator proposed by Skvor, et al. (1992) based on the distributed amplifier. The theoretical analysis presented in Skvor, et al. (1992) was generalized for a distributed oscillator employing m-derived artificial transmission lines. The resulting equations allow predicting the circuit oscillation frequency behavior and the corresponding required minimum transistor transconductances. A design example is described for a three-octave oscillator.

This paper outlines the Microwave Group activities at the Microelectronics Laboratory (LME-University of Sao Paulo) the development of microwave devices for a Satelite Earth Station Receiver over the 3.7 to 4.2 GHz band.

A simple analytical equation is proposed for describing the high-electron-mobility transistor (HEMT) drain current. It has been implemented in the SPICE simulator. It accurately modeled the HEMT transconductance compression and was applied to nonlinear circuit simulation without convergence problems. Using this equation, an oscillator design approach combining linear and nonlinear analysis was used to design a doubly resonant oscillator operating at 18 GHz and using a HEMT in the reverse-channel configuration. The performance of the oscillator confirmed the main results predicted by the simulations. The oscillator generated +11 dBm at 18 GHz, and the circuit-device interaction predicted by the simulation was experimentally confirmed. >

A 1:4/1:16 demultiplexer IC with an integrated skip circuit has been successfully designed and fabricated employing SCFL standard cells based on 1 /spl mu/m MESFET foundry technology. The circuit was designed to operate at up to 2.5 Gb/s with low power dissipation. The demultiplexer employs a tree type architecture based on 1:2 demux blocks using tristage flip-flops. A new skip circuit without re-timing was proposed and integrated in the demultiplexer for frame alignment. The proposed skip circuit demonstrated its effectiveness and the IC operated either as a 1:4 or a 1:16 demultiplexer at up to 2.5 Gb/s with a power dissipation of 1 W. This IC is applicable for signal processing on SONET STS-12/48 optical communication systems.

The Gummel-Poon model implemented in commercial simulators was modified to generate a large-signal model for HBTs. A representation of the thermal effects associated with the DC power dissipated by the device was added to the model and the forward transit time equation was adapted to account for the HBT transit time dependence on the base-collector voltage. The model was applied to a 1.5×20 ?m2 AlGaAs/Gas and gave an adequate representation for the device DC characteristics for current densities up to 105 A/cm2, as well as bias-dependent S parameters up to 50 GHz. At 10 GHz the HBT output power at 1dB gain compression was predicted with less than 1dB error and the third order intercept point with less than 0.8 dB error, for class A and AB bias-points.

This paper presents a set of design equations for spiral and new scalable cross inductors in CMOS 0.35 μm technology, relating electrical parameters of the inductor's equivalent circuit as functions of its geometric dimensions. The procedure used to derive the design equations is described and involves electromagnetic simulation of inductors with different geometric dimensions, extraction of values for equivalent circuit model elements for each inductor and the use of multivariate regression analysis applied to generalized linear models (GLM) based on Design of Experiments (DoE). A nine element π-type equivalent electrical circuit was used for the inductors, where all element values are constants, allowing simulation on SPICE-like software. Results from the models obtained for both spiral and scalable cross inductors presented closely match to the simulated results.

A simple design method for harmonic oscillators using HEMT (high-electron-mobility-transistor) devices is presented. The method employs nonlinear analysis to derive the harmonic components of the drain current of a low-frequency transistor model. The resulting harmonic components are used to linearize a high-frequency model and to synthesize the microwave circuit. A second-harmonic oscillator that uses an X-band dielectric resonator and a packaged HEMT device has +6.0 dBm output power at 18 GHz with 6.5% RF/DC efficiency. >

This thesis aims at developing an impulse radar microwave imaging system applied for breast cancer detection. It proposes solutions focusing on realization of low-cost and portable system prototypes. At first, a breast dielectric tissues study is presented. The relevant dielectric constant difference between a tumor and internal breast tissues is simulated in a heterogeneous breast front-end scenario. A 5th derivative Gaussian pulse is applied to an antenna that illuminates the breast model. The reflected signals are collected from a scenario of 32-antenna positions, covering a 360-degree 2D environment. Microwave Imaging is performed using the Delay and Sum confocal algorithm. Into this issue, improvements are proposed to the algorithm, focusing on tumor borders definition and considering that the tumor is mostly located near the glandular tissue in the ductal region, displaced from the breast center. The algorithm robustness is demonstrated using waveform sets generated from numeric, simulated and experimental scenarios. Subsequently, a study of the power loss by the several breast layers is done, pointing a trade-off between operational frequency, tumor resolution and breast depth. A tissues loss scenario have been calculated and simulated. Using these results, a new antenna-breast medium is proposed concerned with dielectric coupling, mechanical flexibility, comfort and hygienic to the patient. Also based on these front-end studies, a phantom is made to mimic the internal breast tissues, using materials with dielectric properties near to the real ones. Finally, a Microwave Imaging role prototype and a handheld system are realized. A low-cost (US$ 150.00) Commercially Available Off-the-Shelf Impulse Radar Ultra Wideband transceiver platform is used to generate and collect the microwave signals. Firmware, software and communication protocol were developed to allow access to the platform via a Personal Computer. The system is mounted using both the proposed antenna-breast coupling and breast phantom. The prototype and handheld tests were performed in a 2D assembly, where backscattered signals were individually collected at 64 positions, and applied to the improved confocal algorithm. Prototype results showed good location precision, high contrast on tumors borders definition with minimum SCR of 2.17 dB and SMR of 13.68 dB. Furthermore, the handheld implementation resulting reconstructed images presented SCR and SMR above 6.00 dB and 28.00 dB, respectively, and tumor location precision below 0.3 cm. For the proposed hardware, considering an average 15.0 cm diameter breast phantom and a 6.4 GHz operational frequency, a 1.0 cm diameter tumor buried 3.0 cm depth in the breast was detected. These results showed the system feasibility which can be distributed in medical offices, stepping up the total of people with access to early breast cancer diagnosis. Esta tese visa o desenvolvimento de um sistema de imagiologia médica por radar de impulso de micro-ondas para detecção do câncer de mama. Propõe soluções com foco na realização de protótipos de sistemas portáteis e de baixo custo. Inicialmente, é apresentado um estudo de características dielétricas dos tecidos mamários. A relevante diferença na constante dielétrica entre um tumor e os tecidos internos da mama é simulada em um cenário de mama heterogêneo. Um pulso da quinta derivada de uma Gaussiana é aplicado a uma antena que ilumina o modelo da mama. Os sinais refletidos são coletados de forma tomográfica em 32 posições, cobrindo um ambiente em 2D em 360 graus. A geração de imagens por micro-ondas é realizada usando o algoritmo confocal. Neste ponto são propostos aprimoramentos no algoritmo, com foco na definição de bordas do tumor e considerando sua localização próxima ao tecido glandular, na região ductal deslocada do centro da mama. A robustez do algoritmo é demonstrada usando conjuntos de formas de onda gerados a partir de cenários numéricos, simulados e experimentais. Em seguida, é realizado um estudo da perda de potência pelas várias camadas da mama, apontando um compromisso entre frequência operacional, resolução do tumor e profundidade da mama. Um cenário de perda nos tecidos é calculado e simulado. A partir desses resultados, um novo meio de acoplamento antena-mama é proposto com foco no acoplamento dielétrico, flexibilidade mecânica, conforto e higiene ao paciente. Baseado nos estudos do front-end, é construído um phantom que mimetiza os tecidos internos da mama, utilizando materiais com propriedades dielétricas próximas às reais. Finalmente, são montados um protótipo de função e sistema com manopla. Uma plataforma com um transceptor de radar por impulso de banda ultra larga, e de baixo custo (US$ 150,00) disponível comercialmente, é usada para gerar e coletar os sinais de micro-ondas. Firmware, software e protocolo de comunicação foram desenvolvidos para permitir o acesso ao hardware através de um computador pessoal. O sistema é montado usando o acoplamento antena-mama e o phantom propostos. Os testes do protótipo e do dispositivo foram realizados em uma montagem 2D, onde os sinais retroespalhados foram coletados individualmente em 64 posições, e aplicados ao algoritmo confocal aprimorado. Os resultados do protótipo mostraram boa precisão de localização, alto contraste na definição das bordas dos tumores com SCR mínimo de 2,17 dB e SMR de 13,68 dB. Os resultados com a manopla apresentaram SCR e SMR acima de 6,00 dB e 28,00 dB, respectivamente, e precisão de localização do tumor abaixo de 0,3 cm. Usando o hardware proposto num phantom de 15,0 cm de diâmetro com uma frequência operacional de 6,4 GHz, o sistema detectou um tumor de 1,0 cm de diâmetro a 3,0 cm de profundidade. Os resultados mostraram um sistema viável que pode ser distribuído em consultórios, melhorando o acesso ao diagnóstico precoce.

Este trabalho de pesquisa visou ao desenvolvimento de estruturas passivas eletronicamente sintonizáveis operando em frequências da rede 5G abaixo de 6 GHz e sensor de caracterização de líquidos, estabelecendo metodologias de projeto e propondo contribuições originais, no qual, todas as estruturas foram projetadas em tecnologia SIW. Estudos realizados sobre perturbações em cavidades ressonantes, filtros em guias de ondas retangulares, elementos de chaveamento operando em frequências de micro-ondas e sensores de caracterização de líquidos forneceram a base para a elaboração dos procedimentos de projeto. Empregando-se os procedimentos de projeto propostos, foram desenvolvidos: chave eletrônica a diodo PIN de baixas perdas e custo reduzido; três cavidades ressonantes sintonizáveis mecânica e eletronicamente; filtro passa-faixa com largura de banda sintonizável eletronicamente; e sensor de caracterização de líquidos. A chave a diodo PIN utiliza linhas de transmissão ao invés de componentes concentrados, reduzindo perdas por inserção e custo de fabricação, e foi projetada para operar na frequência de 3,5 GHz. Duas cavidades ressonantes, sendo uma retangular e outra quadrada, têm sua sintonia feita de maneira mecânica, ou seja, pela conexão direta de poste metálico alocado no centro da cavidade, interligando paredes superior e inferior. A cavidade retangular é sintonizável nas frequências de 5,0 GHz e 6,0 GHz, já a cavidade quadrada é sintonizável nas frequências de 6,0 GHz e 7,2 GHz. A terceira cavidade é sintonizável eletronicamente nas frequências de 3,4 GHz e 4,0 GHz por meio de uma chave a diodo PIN alocada sobre a parede superior da cavidade, no qual, a chave eletrônica utiliza linhas de transmissão e somente um capacitor de bloqueio de corrente contínua, sendo a integração dessa chave à estrutura SIW uma contribuição original. O filtro passa-faixa tem frequência central de 3,5 GHz e largura de banda sintonizável, larguras de banda de 10 dB de 6,23% e 0,714%, por meio de oito chaves a diodos PIN, chaves eletrônicas que utilizam linhas de transmissão e somente um capacitor, alocadas sobre a parede superior do guia de ondas e são responsáveis pelo chaveamento de oito postes metálicos, que atuam como descontinuidades indutivas, de mesmo diâmetro inseridos no volume interno do guia de ondas em tecnologia SIW. Este filtro passa-faixa apresentou duas contribuições originais: uma nova configuração no posicionamento das descontinuidades indutivas que permitiu a miniaturização do filtro; é o primeiro a utilizar várias chaves a diodos PIN com linhas de transmissão e somente um capacitor. O sensor de caracterização de líquidos proposto é uma nova alternativa de baixo custo e confiável para obter a constante dielétrica e caracterizar líquidos, sendo composto por uma cavidade ressonante híbrida, que utiliza conceitos das tecnologias dos guias de ondas retangulares e SIW. Os comportamentos previstos teoricamente para as estruturas projetadas são confirmados por meio de simulação eletromagnética computacional e medição experimental, indicando a validade dos métodos adotados. Os avanços obtidos neste trabalho de pesquisa são identificados examinando-se outros trabalhos científicos já publicados. Este trabalho foi desenvolvido de maneira integral no Laboratório de Microeletrônica da Escola Politécnica da Universidade de São Paulo. This research work aimed at the development of electronically tunable passive structures operating in frequencies of 5G network below 6 GHz and liquids electrical characterization sensor, establishing design methodologies and proposing novel contributions, where all structures were designed in SIW technology. Studies performed on perturbations in resonant cavities, filters in rectangular waveguide technology, switching devices operating in microwave frequencies, and liquids electrical characterization, provided the theoretical base to develop the design procedures. Employing the proposed design procedures were developed: a low-cost and low losses PIN diode switch; three tunable resonant cavities with mechanical and electronic tuning; a tunable bandpass filter; and a liquids electrical characterization sensor. The PIN diode switch uses transmission lines instead of lumped components, reducing the insertion losses and fabrication cost, is designed to operate at 3.5 GHz. Two resonant cavities, a square cavity and a rectangular cavity, have a mechanical tuning by a direct connection of the metal post located at the center of the resonant cavities, connecting the bottom and top walls. The rectangular cavity is tunable at the frequencies of 5,0 GHz and 6,0 GHz, and the square cavity is tunable at 6,0 GHz and 7,2 GHz. The third cavity is electronically tunable at the frequencies of 3,4 GHz and 4,0 GHz by a PIN diode switch with transmission lines and only one DC block capacitor, where the assembling of this switch is a novel contribution. The bandpass filter has a central frequency of 3,5 GHz and tunable bandpass, 10 dB bandpass of 6,23% and 0,714%, by eight PIN diode switches, electronic switches employing transmission lines and one DC block capacitor, located on the top wall of the waveguide and are responsible by the switching of the eight metal posts, acting as inductive discontinuities, with the same diameter inserted into the internal volume of the waveguide in SIW technology. This bandpass filter presented two novel contributions: a novel offset post arrangement that allowed a compact structure; it is the first filter that uses various PIN diode switches employing only one DC block capacitor and transmission lines assembled on the top wall. The proposed liquids electrical characterization sensor is low-cost and reliable, being considered a new alternative to obtain the dielectric constant and characterize liquids. The sensor is composed of a hybrid resonant cavity, using concepts of rectangular waveguide and SIW technologies. The theoretically predicted behaviors for the designed structures are confirmed by computational electromagnetic simulations and experimental results, indicating the validity of the adopted methods. The obtained achievements in this research work are identified by others published works. This work was fully developed in the Microelectronics Laboratory of the Polytechnic School of the University of São Paulo.

Este trabalho visou ao desenvolvimento de antenas de ressoador dielétrico de banda dupla em frequências de micro-ondas por meio do estabelecimento de uma metodologia de projeto para as mesmas e da proposição de configurações inéditas de antenas desse tipo. Estudos realizados sobre antenas de ressoador dielétrico e sobre suas técnicas de projeto forneceram a base para a elaboração de um procedimento de projeto para antenas de banda dupla que explora a flexibilidade das antenas de ressoador dielétrico. Empregando-se esse procedimento de projeto, duas antenas com configurações originais foram desenvolvidas para operar em frequências de micro-ondas. Uma delas é uma antena de ressoador dielétrico cilíndrica sobre plano de terra, destinada a operar nas frequências centrais de 3,94 GHz e de 5,42 GHz, com diagrama de radiação direcional e polarização circular na primeira banda de operação e com diagrama de radiação omnidirecional e polarização linear na segunda. A outra antena consiste em uma antena de ressoador dielétrico cilíndrica sobre substrato dielétrico aterrado, cujas frequências centrais de operação são 3,99 GHz e 6,20 GHz, com diagrama de radiação direcional e polarização circular em ambas as bandas de operação. O projeto das duas antenas também levou a contribuições novas adicionais em alguns temas específicos relacionados: estruturas de excitação para antenas de ressoador dielétrico, circuitos acopladores híbridos de 90° de banda dupla, circuitos de alimentação para antenas de banda dupla e modelos matemáticos para o ressoador dielétrico cilíndrico isolado no espaço livre. Os comportamentos previstos teoricamente para as antenas projetadas são confirmados por meio de resultados obtidos por simulação eletromagnética e por medição experimental, o que indica a validade das hipóteses adotadas, das configurações de antena propostas e da metodologia de projeto concebida, demonstrando também a flexibilidade desta para variadas especificações de antena. Os avanços obtidos com este trabalho e as melhorias que podem ser efetuadas sobre o mesmo são identificados examinando-se resultados recentemente publicados na literatura técnica. Este trabalho foi realizado na forma de uma pesquisa de doutorado sanduíche, desenvolvida parcialmente na University of Houston sob a supervisão do Prof. Stuart A. Long. This work aimed at the development of microwave dual-band dielectric resonator antennas by means of establishing a design methodology for them and of proposing novel configurations of this antenna type. Studies on dielectric resonator antennas and on their design techniques provided the ground for elaborating a design procedure for dual-band antennas that exploits the flexibility of dielectric resonator antennas. By employing this design procedure, two antennas with original configurations have been developed for operation at microwave frequencies. One of them is a cylindrical dielectric resonator antenna on a ground plane, intended for operation at the center frequencies of 3.94 GHz and 5.42 GHz, with a directional radiation pattern and circular polarization in the first operating band and with an omnidirectional radiation pattern and linear polarization in the second one. The other antenna consists of a cylindrical dielectric resonator antenna on a grounded dielectric substrate, whose operating center frequencies are 3.99 GHz and 6.20 GHz, with a directional radiation pattern and circular polarization in both operating bands. The design of the two antennas also led to additional new contributions in some related specific subjects: excitation structures for dielectric resonator antennas, dual-band 90°-hybrid couplers, feeding circuits for dual-band antennas, and mathematical models for the cylindrical dielectric resonator isolated in free space. The behaviors theoretically expected for the designed antennas are confirmed by means of results obtained from electromagnetic simulation and from experimental measurements, which indicates the validity of the assumed hypotheses, of the proposed antenna configurations and of the conceived design methodology, also demonstrating the flexibility of the latter for various antenna specifications. The advances obtained with this work and the improvements that can be made on it are identified by examining results recently published in the technical literature. This work was carried out as a sandwich doctoral research, developed at the University of Houston under the supervision of Prof. Stuart A. Long.

Nesta tese desenvolveram-se projetos e modelos de indutores planares para circuitos integrados de radiofrequência nas arquiteturas espiral e cross para as tecnologias CMOS AMS 0,35 ?m e IBM 0,13 ?m, visando representar o desempenho destes na faixa de frequências de corrente contínua até 90% da frequência de ressonância. A modelagem empregada utiliza um circuito elétrico equivalente com nove elementos para representar indutores, para o qual é apresentado um processo para extração dos valores dos seus componentes a partir de dados simulados ou medidos. Foi apresentada uma versão estendida da arquitetura cross original, mais flexível e tratável por algoritmos, com uma indutância 25% maior que a arquitetura espiral de mesma área. Utilizou-se planejamento de experimentos para elaborar conjuntos de amostras de indutores com dimensões geométricas variadas nas arquiteturas e tecnologias estudadas, para os quais desenvolveu-se um conjunto de algoritmos específicos para o projeto dos indutores a partir de suas dimensões. A simulação eletromagnética do layout de cada amostra gerou os resultados empregados no desenvolvimento do processo de extração dos valores dos componentes do circuito equivalente, os quais foram relacionados às dimensões geométricas dos indutores através de equações de projeto elaboradas por meio de análise de regressão multivariada e modelos lineares generalizados. Tanto o processo de extração dos valores dos componentes, como as equações de projeto foram validados estatisticamente pela comparação dos resultados das simulações dos respectivos circuitos equivalentes com os resultados das simulações eletromagnéticas dos layouts dos indutores em cada arquitetura e tecnologia, demonstrando a correspondência entre estes. Discrepâncias observadas em alta frequência entre os resultados de simulação eletromagnética dos indutores e seus respectivos circuitos equivalentes são associados a limitações do modelo de circuito usado, que não considera os fenômenos de correntes de Foucault (correntes de turbilhonamento) e efeito pelicular. O processo de modelagem desenvolvido, devido a sua generalidade, pode ser aplicado ao desenvolvimento de outros modelos de circuito elétrico para indutores, ou mesmo para modelagem de outros componentes passivos para circuitos integrados, como capacitores, resistores e transformadores. In this thesis were developed designs and models for planar inductors for radiofrequency integrated circuits in the spiral and cross architectures for AMS 0.35 ?m and IBM 0.13 ?m CMOS technologies, aiming to represent the inductors performance in the frequency range of direct current up to 90% of resonant frequency. The employed modeling used an equivalent circuit for inductors with nine elements, for which a process for extracting the values of its components from simulated or measured data is presented. An extended version of the original cross architecture was presented, more flexible and treatable by algorithms, with an inductance 25% larger than the spiral architecture of the same area. Design of experiments was used to elaborate sets of inductor samples with different geometric dimensions in the studied architectures and technologies. Algorithms were developed to design the layout of each inductor considering its architecture and specific dimensions. The layout electromagnetic simulation of each sample generated the results used in the process developed for extracting the values of the components of the equivalent circuit model, which were related to the geometric dimensions of the inductors through design equations elaborated by multivariate regression analysis and generalized linear models. Both the component extraction process and the design equations were statistically validated by comparing the simulation results of the respective equivalent circuit models with the results of the electromagnetic simulations of the inductor layouts in each architecture and technology, demonstrating matching between them. Observed discrepancies at high frequency between the electromagnetic simulation results for the inductors and their respective equivalent circuits are associated with limitations of the circuit model used, which does not consider eddy currents and skin effect phenomena. The modeling process developed, due to its generality, can be applied to the development of other electric circuit models for inductors, or even to model other passive components for integrated circuits, such as capacitors, resistors and transformers.

Neste trabalho, foram desenvolvidas antenas têxteis de micro-ondas para aplicação em sistemas vestíveis, operando nas bandas ISM de 2,45 GHz e 5,8 GHz. Foram compiladas informações sobre o estado da arte em antenas têxteis, sendo realizado um estudo sobre antenas planares de micro-ondas e técnicas de alimentação das mesmas. Foi feita uma prospecção dos processos de fabricação de antenas têxteis de micro-ondas, definindo-se o processo e materiais têxteis usados na construção das antenas desenvolvidas. Procedeu-se à caracterização do tecido usado como substrato das antenas determinando-se suas características eletromagnéticas, utilizadas no projeto das antenas. Foram desenvolvidas antenas de microfita com plaqueta retangular e alimentação por sonda coaxial, para banda ISM de 2,45 GHz. Investigou-se o efeito da espessura do substrato da antena, tendo-se obtido experimentalmente larguras de banda de 4,8% e 6,0% para substratos com 0,7 mm e 1,4 mm de espessura, respectivamente. Foi proposta uma antena de microfita alimentada via acoplamento por proximidade que integra um transformador de um quarto de comprimento de onda ao circuito de alimentação, resultando em alargamento de banda da antena. Essa configuração foi utilizada no projeto de quatro antenas, que demonstraram experimentalmente larguras de banda de 11,2%, 13,4%, 17,0% e 24,0%. Uma configuração de antena têxtil empregando cavidade de um quarto de modo foi proposta para operação em banda dupla, sendo a tecnologia de guia de ondas integrado ao substrato - SIW, empregada em sua fabricação. Foi desenvolvido um procedimento de projeto para essa antena, o qual foi aplicado ao projeto de uma antena de banda dupla para as faixas ISM e 2,45 GHz e 5,8 GHz. Os resultados experimentais demostraram operação em banda dupla, com largura da banda inferior de 9,3%, e largura da banda superior de 9,2%. A antena de cavidade de quarto de modo apresentou as vantagens de maior ganho e menores dimensões relativamente às antenas têxteis de microfita desenvolvidas. De forma geral, os resultados experimentais dos protótipos construídos apresentaram boa concordância com os resultados fornecidos por simulação, demonstrando que as configurações de antenas propostas atenderam a seus objetivos, e a efetividade dos procedimentos de projeto adotado. In this work, textile microwave antennas for use in wearable systems operating at 2.45 GHz and 5.8 GHz ISM bands were developed. Information on the state of art in textile antennas were compiled, and a study on microwave planar antennas and feeding techniques was performed. Processes for manufacturing textile microwave antennas were presented, and the fabrication process and textile materials used in this work were defined. The electromagnetic characteristics of the fabric used as antenna substrate were experimentally obtained, and used in the antenna design. Microstrip antennas using rectangular patch and coaxial probe feed were designed to operate at the 2.45 GHz ISM band. The effect of the antenna substrate thickness on the antenna characteristics was investigated, and experimental bandwidths of 4,8% and 6% were demonstrated for antennas with 0.7 mm and 1.4 mm thick substrates, respectively. A microstrip antenna fed by proximity coupling, including a quarter wavelength transformer at the feeding circuit, was proposed, resulting in the widening of the antenna bandwidth. This configuration was used to design four antennas, which experimentally demonstrated bandwidths of 11.2%, 13.4%, 17.0% and 24.0%. A textile antenna configuration employing a fourth mode cavity was proposed for dual band operation. Substrate integrated waveguide technology - SIW, was used for the antenna manufacturing. A design procedure was developed for this antenna, which has been applied to the design of a dual band antenna for the 2.45 GHz and 5.8 GHz ISM bands. The experimental results of this antenna demonstrated dual band operation, with 9.3% bandwidth at the lower band and 9.2% bandwidth at the higher band. The quarter mode cavity antenna presented the advantages of increased gain and smaller area than the designed textile microstrip antennas. In general, the experimental results of the fabricated prototypes exhibited good agreement with the results provided by simulation, demonstrating that the textile antenna configurations proposed met their expected performance and validating the design procedures adopted.

Este trabalho apresenta o projeto de uma portadora que opera na frequência de 8.300 MHz para ser utilizado em moduladores vetoriais diretos com aplicação em sistemas embarcados de satélites. Foram realizados estudos sistêmicos de arquiteturas que operam nesta faixa de frequência com as características necessárias para atender as especificações da European Cooperation for Space Standardization, ECSS - Space Engineering Radio Frequency and Modulation da agência espacial europeia -ESA, que regulamenta as frequências e características para sistemas de transmissão para enlace de descida. A partir dos conhecimentos adquiridos nos estudos, é apresentada uma metodologia de projeto visando o atendimento das especificações definidas pela ECSS e a escolha de uma topologia de projeto. Foram realizadas simulações a nível sistêmico, utilizando o software Advanced Design System-ADS da fabricante Keysight Technologies, para definir as especificações de projeto dos circuitos que compõem o sistema de geração da portadora na banda X. O circuito da malha de sincronismo de fase - PLL opera na frequência de 2.075 MHz, onde seu sinal é amplificado e filtrado pela cadeia de amplificação na banda S cuja função é aumentar a isolação para minimizar os efeitos de pulling do oscilador controlado por tensão - VCO, devido à alta velocidade nas transições de tempo de subida e de descida dos sinais digitais I e Q. O filtro também é responsável por aumentar a rejeição de espúrios e harmônicos gerados pelos efeitos não lineares dos amplificadores. O sinal é enviado ao circuito multiplicador de frequências que gera o sinal na banda X e é filtrado por um filtro passa-faixas de linhas acopladas, rejeitando os sinais espúrios provenientes da saída do multiplicador de frequência. Na saída, o sinal passa por uma cadeia de amplificação na banda X para adequar o nível de potência à entrada dos moduladores vetoriais. Os circuitos projetados foram desenvolvidos utilizando tecnologia de microfita de linha. Os protótipos foram caracterizados, apresentando boa concordância com os resultados simulados, comprovando experimentalmente a metodologia de projeto utilizada neste trabalho assim como o atendimento das especificações sugeridas pela ECSS. This work presents the project of an carrier that works in the frequency of 8,300 MHz to be used in direct vector modulator for embedded system application in satellites. It were realized system level studies of PLL topologies that work in this frequency range with the necessary features to provide the requirements from European Cooperation for Space Standardization, ECSS - Space Engineering Radio Frequency and Modulation of the European Space Agency - ESA, which is responsible for the frequencies and features regulation for downlink transmission system. With the knowledge acquired from the studies, it is presented a project method intending to the meet the requirements defined by the ECSS and the definition of a topology to the project. It were performed system level simulation, using the Advanced Design System - ADS tool, from Keysight Technologies, in order to define the design specifications in the project of the circuits of the X band carrier generator developed. The PLL circuit works in the frequency of 2,075 MHz, in which its signal is amplified and filtered for amplifier chain in S band, increasing the isolation to reduce the pulling effects in the voltage controlled oscillator, due to the high-speed transitions in the rise time and fall time of the digital signal I and Q. The filter is also responsible for increasing the rejection of spurious and harmonics generated by non-linear amplifiers effects. The signal is conducted to the frequency multiplier circuit that generates the X band signal and it is filtered by a coupled line bandpass filter, rejecting the spurious from the frequency multiplier output. At the output stage, the signal passes through a X band amplification chain in order to adequate the power level of the vector modulators input level. The specified circuits were designed and developed using microstrip line technology. The prototypes were characterized, presenting adequate results according to the data obtained by the simulations, experimentally reinforcing the project method used in this work as well as the meeting of the requirements suggested by the ECSS.

Etanol é um dos principais combustíveis na matriz energética brasileira. Embora tenha uma fiscalização rigorosa, é comum sua adulteração com água. Este trabalho propõe o desenvolvimento de sensores planares de micro-ondas para a qualificação de etanol combustível. São apresentados dois conjuntos de sensores, sendo um voltado para a análise da fase vapor e outro para a fase líquida do etanol combustível. Foram projetados dois sensores para a fase vapor, sendo um deles uma antena de microfita e o outro uma antena de fenda em cavidade de guia de ondas integrada ao substrato, ambos recobertos com nanotubos de carbono e operando em 5,8 GHz. As antenas foram utilizadas como ressoadores e não como elementos radiantes. Os dois sensores para a fase líquida foram projetados em tecnologia de guia de ondas integrado ao substrato, sendo um deles a antena de fenda em cavidade, sem cobertura de nanotubos de carbono, e o outro um guia de ondas operando na faixa de 3,95 a 6 GHz contendo uma seção no substrato. Foram implementadas as técnicas de perturbação da cavidade ressonante e de transmissão/reflexão para a extração dos valores de permissividade elétrica complexa dos materiais sob teste, a partir da resposta em frequência dos sensores propostos. Foram caracterizadas amostras de álcool etílico absoluto 99,5%, água deionizada e misturas desses materiais em diferentes frações. Todos os sensores propostos demonstraram capacidade de discriminação de frações volumétricas de etanol em água de 2% (v/v) na faixa especificada pela legislação. Os nanotubos de carbono viabilizaram o desenvolvimento dos sensores de fase vapor, sendo que o sensor empregando a antena com fenda apresentou sensibilidade 5,1 vezes maior comparado ao sensor com antena de microfita. O sensor de fase líquida usando a antena com fenda apresentou a maior sensibilidade entre os sensores ressonantes -- 30,9 vezes maior do que o obtido com a antena de microfita com nanotubos de carbono. O sensor com guia de ondas integrado ao substrato apresentou incerteza máxima de 3,4% para medidas de etanol em água nas frações permitidas pela legislação. Dessa forma, este trabalho contribui de forma original no desenvolvimento de sensores para caracterização eletromagnética de materiais e para qualificação de etanol combustível. Ethanol is one of the main fuels in the Brazilian energy matrix. Despite going through rigorous inspection, it is usually altered with water. This work proposes different planar microwave sensors for qualifying ethanol fuel. Two sets of sensors are presented: one for analyzing the vapor phase of ethanol and the other for the liquid phase of ethanol. Two sensors were designed for the vapor phase: a microstrip antenna and a cavity-backed slot antenna based on the substrate integrated waveguide technology, both coated with carbon nanotubes and operating at 5.8 GHz. The antennas were used as resonators and not as radiation elements. The sensors for the liquid phase were also designed based on the substrate integrated waveguide technology. The first sensor is a cavity-backed slot antenna, without carbon nanotubes, and the second sensor is a waveguide containing a section in the substrate, which operates at frequencies from 3.95 to 6 GHz. The cavity perturbation technique and the transmission/reflection method were implemented to extract the complex permittivity values from the materials under test, from the frequency response of the sensors. Samples of ethanol 99,5% pure, deionized water, and mixture with different proportions of these two materials were characterized. All the proposed sensors demonstrated capacity to differentiate 2% (v/v) of volumetric fraction of ethanol in water within the range specified by the legislation. Carbon nanotubes allowed the development of the vapor phase sensors. The vapor phase sensor using the cavitybacked slot antenna presented 5.1 times higher sensitivity compared to the sensor employing the microstrip antenna. The liquid phase sensor using the cavity-backed slot antenna presented the highest sensitivity among the resonant sensors -- 30.9 times higher than the microstrip antenna with carbon nanotubes. The sensor with substrate integrated waveguide presented uncertainty 3.4% for fractions of ethanol in water allowed by the legislation. Thus, this work provides an original contribution to the development of electromagnetic sensors for the characterization of materials and for qualifying ethanol fuel.

Esse trabalho de pesquisa apresenta um estudo detalhado sobre guias de ondas integrados ao substrato (SIW) operando em frequências de micro-ondas com base na teoria de guias de ondas retangulares (RWG). O estudo sobre guias SIW associa equações apresentadas na literatura e utiliza simulações eletromagnéticas para desenvolver um procedimento de projeto bem definido. É considerada a integração entre guias SIW e linhas de transmissão de microfita, projetando-se transições entre essas duas estruturas com o propósito de prover casamento de impedância e de viabilizar a caracterização em frequências de micro-ondas. São apresentadas considerações sobre processos de fabricação de circuitos SIW em substratos constituídos por laminados de alta frequência. Uma vez estabelecidos os procedimentos de fabricação e os critérios de projeto, a tecnologia SIW é aplicada ao projeto de três guias de ondas SIW nas bandas S e X, que foram fabricados empregando laminados de alta-frequência. Foram projetados dois filtros SIW passa-faixa empregando cavidades ressonantes e postes metálicos indutivos. Os dois filtros operam na frequência central de 10,61 GHz, sendo que um deles tem banda de passagem de 7,5%e é de 3ª ordem e o outro filtro tem banda de passagem de 15%, sendo de 5ª ordem. Foram realizadas comparações entre o desempenho simulado e experimental das estruturas SIW projetadas. Os resultados de simulações eletromagnéticas e experimentais demonstraram boa concordância. Os projetos em tecnologia SIW apresentados neste trabalho de pesquisa possuem perdas de retorno melhores que 10 dB na banda de operação e perdas por inserção de 1,0 dB a 1,5 dB. É apresentada a análise da sensibilidade do desempenho dos guias de ondas e filtros SIW projetados a desvios dimensionais típicos do processo de fabricação por microfresagem mecânica. Com os resultados experimentais e de simulação foi possível validar os procedimentos de projeto e de fabricação de circuitos SIW operando em frequências de micro-ondas. This research work presents a detailed study about substrate integrated waveguide (SIW) operating in microwave frequencies based on rectangular waveguides (RWG) theory. The study about SIW associates equations presented at the literature and uses electromagnetic simulations to develop a well-defined design procedure. Is considered the integration between substrate integrated waveguides and microstrip line, designing transitions between these two structures with the aim to provide impedance matching and make possible the characterization in microwave frequencies. Considerations are made about the manufacturing process of the SIW circuits on planar dielectric substrate. Once established a manufacturing process and a design procedure, the SIW technology is applied in three waveguides to operate in S and X bands. Was designed two band-pass filters with central frequency of 10,61 GHz, where one of them has band-pass of 7,5% and it is third order filter and the another one has band-pass of 15,0% and it is five order filter. Was made comparison between simulated results and experimental results for the all designed structures. The simulated results and the experimental results shown good agreement. The projects in SIW technology shown in this research work has return loss better than 10dB in the operation band and insertion loss between 1,0 dB and 1,5dB. Is shown a sensibility analysis of the waveguides and filters performance in SIW technology to evaluate the layout differences caused by manufacturing process. With the experimental results and simulation results was possible validate the design procedures and the manufacturing process of the SIW circuits operating in microwave frequencies.

Neste trabalho investiga-se, inicialmente, o comportamento de um amplificador klystron de múltiplas cavidades segundo uma análise a pequenos sinais linear considerando o efeito de carga espacial para, na seqüência, apresentar uma análise do dispositivo utilizando um modelo não-linear a grandes sinais. Na primeira investigação apresenta-se, a partir da teoria dos modos normais, expressões que descrevem o balanço de potência complexo em uma cavidade excitada por um feixe de elétrons. Na seqüência, utiliza-se um modelo linearizado a pequenos sinais para desenvolver uma expressão para a densidade de corrente de convecção ao longo do tubo de deriva acoplado a múltiplas cavidades reentrantes, em função do campo elétrico produzido nos gaps de interação das cavidades. Estas expressões formam a base para a determinação do ganho de voltagem e de ganho de potência de um amplificador klystron de múltiplas cavidades, além da determinação de uma expressão para a largura de banda, sob a hipótese de cavidades idênticas e igualmente espaçadas. O código desenvolvido é validado utilizando-se os parâmetros de um amplificador klystron de 4 cavidades, com corrente d.c. de 525 mA, voltagem d.c. de 6 kV e freqüência de 1,849 MHz, quando se obteve um ganho de 70 dB. Na análise a grandes sinais, o modelo matemático utiliza o formalismo lagrangiano para resolver a dinâmica das partículas, descritas conforme o modelo de discos com raio finito, em uma análise unidimensional, considerando os efeitos não-lineares devido aos campos de carga espacial. O código é validado usando os dados de um amplificador klystron comercial Varian. Dentre outros, os gráficos da velocidade e da densidade do feixe de elétrons, da corrente harmônica, do ganho por cavidade, da conversão AM/AM, da compressão de ganho e da energia do sistema são mostrados e discutidos. Além disso, apresentou-se também um método para a determinação da freqüência de ressonância 0 f , para o fator de qualidade Q e para a razão (R Q) em cavidades cilíndricas reentrantes, de relevância para o projeto de amplificadores klystron de múltiplas cavidades, utilizando a técnica do casamento de admitância do gap de interação entre a cavidade e o tubo de deriva. Um dos resultados mais significativos é o da corrente harmônica fundamental, que resultou 60% maior do que a corrente d.c. considerando um dispositivo com 4 cavidades. This work investigates, initially, a klystron amplifier with multiple cavities using a small signal analysis considering the space charge effects for, in sequence, provide an analysis of the device using a model for large signals. In the first investigation is presented, from the normal modes theory according to J. Slater, expressions that describe the complex balance of power in a cavity excited by an electron beam. Subsequently, it uses a linearized model for small signals to develop an expression for the convection current density along the drift tube coupled to multiple reentrant cavities, depending on the electric field produced in the interaction gaps of the cavities. These expressions form the basis for determining the voltage gain and power gain of an amplifier klystron to multiple cavities, and determination of an expression for the bandwidth, under the hypothesis of identical and equally spaced cavities. The developed code is validated using the parameters of a klystron amplifier, four cavities, with dc current 525 mA, dc voltage of 6 kV, and frequency of 1.849 GHz, when it obtained a gain of 70 dB. In the large signal analysis, the mathematical model uses the lagrangian formalism to solve the dynamics of particles, described as the model disk with finite radius in a one-dimensional analysis, considering the nonlinear effects due to space charge fields. The code is validated using data from a commercial Varian klystron amplifier of 1.848 GHz. Among others, the graphs of velocity and density of the electron beam, the harmonic current, the gain per cavity, the conversion AM/AM compression gain and energy of the system are shown and discussed. Moreover, it is presented a method for determining the resonant frequency 0 f , for the quality factor Q and the (R Q) at reentrant cylindrical cavities, of relevance for the design of a klystron amplifier of multiple cavities, using the admittance matching technique in the gap of interaction between the cavity and drift tube. One of the more significant is the fundamental harmonic current, which resulted 60% higher than the dc current considering a device with four cavities.

A existência de ondas gravitacionais foi confirmada indiretamente pela observação astronômica de pulsares binários. Detectores de ondas gravitacionais tem sido desenvolvidos desde o trabalho pioneiro de Weber nos anos 60. Esforços estão sendo realizados no sentido de aumentar a sensibilidade dos detectores e realizar uma detecção direta, que ainda não foi confirmada. O Grupo GRAVITON está aperfeiçoando e melhorando a sensibilidade de um detector de ondas gravitacionais que se encontra no Laboratório de Estado Sólido e Baixas Temperaturas do Instituto de Física da Universidade de São Paulo (LESBT/IFUSP), na cidade de São Paulo com apoio da FAPESP (processo 2006/56041-3). Esse detector, denominado MARIO SCHENBERG, é composto por uma massa ressonante esférica de CuAl(6%) com 65 cm de diâmetro, com aproximadamente 1150 kg, que deverá atingir a sensibilidade h ~ 10-22 em uma banda passante de 50 Hz, em torno de 3200 Hz, quando estiver operando a temperaturas da ordem de 0,05 K. Atualmente o detector já tem toda a sua infraestrutura criogênica montada e testada para resfriamentos a 4 K e toda a suspensão da esfera bem como todo o sistema de filtragem mecânica construídos e montados. Já foram realizadas as primeiras corridas comissionadas em 2006, 2007 e 2008, quando foram realizados vários diagnósticos sobre o sistema e desde então vem sendo desenvolvidos os transdutores para colocar o detector novamente em operação com melhor sensibilidade. Paralelamente, foram realizadas melhorias no próprio detector em razão dos diagnósticos realizados. O trabalho aqui apresentado está associado ao projeto acima. O autor desenvolveu atividades associadas à construção e desenvolvimentos do detector, que podem ser divididas em três partes principais: na parte mecânica, foi desenvolvido, instalado e testado um novo sistema de isolamento vibracional da suspensão da esfera; na parte criogênica foram feitas novas conexões térmicas, cálculos de gastos de hélio líquido e feitos desenvolvimentos para o funcionamento do refrigerador por diluição; e na parte eletrônica foi feita a instalação da eletrônica responsável pela transdução do sinal, além do desenvolvimento de um novo par de antenas de microfita. The existence of gravitational waves has been confirmed indirectly by astronomical observation of binary pulsars. Gravitational wave detectors have been developed since the pioneering work of Weber in the 60s. Efforts are being made to increase the sensitivity of the detectors and perform a direct detection, wich has not been confirmed yet. The GRAVITON Group is enhancing and improving the sensitivity of a gravitational wave detector which is at the Laboratório de Estado Sólido e Baixas Temperaturas of the Instituto de Física of the Universidade de São Paulo (LESBT / IFUSP), in São Paulo city and is supported by FAPESP (processo 2006/56041-3). This detector, called MARIO SCHENBERG, consists of a spherical resonant mass of CuAl (6%) with 65 cm in diameter, and approximately 1150 kg, which should reach the sensitivity of h ~ 10-22 in a bandwidth of 50 Hz around 3200 Hz, when operating at temperatures of 0.05 K. Currently the detector already has all its infrastructure assembled and tested for cryogenic cooling down to 4 K and the whole suspension of the sphere as well as all mechanical isolation system constructed and assembled. Commissioning runs have already been done in 2006, 2007 and 2008, when several diagnoses on the system were performed and since then there have been many developments on the transducers to put back the detector into operation with improved sensitivity. At the same time, improvements have been made within the detector itself due to the diagnoses. The work presented here is associated with the above project. The author has developed activities and developments associated with the detector construction, which can be divided into three main parts: the mechanical part, in which a new system of vibration isolation was designed for the sphere suspension, installed and tested; the cryogenic part, in which new connections and thermal calculations of liquid helium boil-off rate were made as well as other developments for the operation of a dilution refrigerator; and the electronic part, in which the installation of the electronic signal responsable for the transduction was made, besides the development of a new pair of micro-strip antenna.

Esta dissertação propõe uma metodologia de projeto de osciladores distribuídos controlados por tensão - DVCO - com realimentação reversa em freqüência de microondas. Estes constituem uma nova classe de osciladores recentemente proposta, a qual é obtida através da realimentação reversa de amplificadores distribuídos e tem como principal vantagem a possibilidade de sintonia em faixa ultra-larga de freqüência. São apresentados os fundamentos teóricos de operação do circuito e é proposta uma extensão da análise linear apresentada na literatura, considerando linhas de transmissão artificiais m-derivadas, a qual permite prever as transcondutâncias mínimas necessárias dos transistores e a freqüência inicial de oscilação. O método de projeto proposto é direcionado a DVCOs com realimentação reversa empregando transistores de efeito de campo dos tipos MESFET (Metal Semiconductor Field Effect Transistor) e PHEMT (Pseudomorfic High Electron Mobility Transistor), bem como ao uso de tecnologia de circuitos híbridos de microondas - MICs, e circuitos integrados monolíticos de microondas - MMICs. A metodologia proposta definiu critérios para implementar a topologia deste circuito através de componentes reais, considerando-se os parasitas associados aos mesmos. Para validação do procedimento de projeto, concebeu-se e simulou-se através do programa ADS da Agilent um oscilador intitulado DVCO 3 GHz, cuja faixa de freqüência especificada estende-se de 1 a 3 GHz e a potência mínima de saída especificada é de 10 dBm. Um protótipo foi construído em circuito híbrido e seus resultados experimentais foram comparados aos simulados. A freqüência de oscilação medida foi de 1,04 GHz a 3,05 GHz e a potência obtida esteve entre 9,8 e 14,3 dBm, apresentando boa concordância com as simulações. O ruído de fase foi medido entre 100 kHz e 1 MHz de distância da portadora, observando-se uma inclinação proporcional a 1/f3. Verificou-se que a diminuição da corrente de polarização Ids dos transistores, através da redução de sua tensão de polarização de porta-fonte Vgs, melhorou o ruído de fase. Na condição de polarização de menor ruído de fase, observaram-se valores entre -84 e -93 dBc/Hz a 100 kHz da portadora. In this dissertation, a design methodology applied to microwave reverse feedback distributed voltage controlled oscillators - DVCO - is proposed. This circuit constitutes a new class of oscillators, obtained from reverse feeding back of the distributed amplifier. The main advantage of this topology is its capacity to achieve ultra-wideband frequency tuning. Circuit theoretical background is presented and an extension of the linear analysis presented in the literature is proposed. It allows predicting transistor minimum transconductances and the oscillation initial frequency, considering m-derived artificial transmission lines. The proposed design method is applicable to reverse feedback DVCOs employing field effect transistors MESFET (Metal Semiconductor Field Effect Transistor) and PHEMT (Pseudomorfic High Electron Mobility Transistor), as well as using MIC (Microwave Integrated Circuits) and MMIC (Monolithic Microwave Integrated Circuits) technology. The proposed methodology defined criterion to employ real components, considering the component parasitics. In order to validate the design method, an oscillator named DVCO 3 GHz was designed and simulated through software Agilent ADS, with specified band from 1 up to 3 GHz and minimum output power of 10 dBm. A prototype was implemented in hybrid circuit technology and the measurements were compared to the simulation results. The measured oscillation frequency varied from 1,04 GHz up to 3,05 GHz and the output power was 9,8 to 14,3 dBm, presenting good agreement with simulations. Phase noise was measured in the range between 100 kHz and 1 MHz shift from carrier; in which it was observed a 1/f3 slope. It was verified that decreasing the transistor bias current Ids through decreasing its gate bias voltage Vgs reduced phase noise. In the biasing condition for lowest phase noise, values between -84 and -93 dBc/Hz at 100 kHz off-set from carrier were measured.