<p> A detailed theoretical analysis of the propagation constant and the field components in rectangular waveguide completely filled with a semiconductor subjected to an external transverse applied magnetic field, has been carried out. A numerical solution of the transcendental equation for the propagation constant has been obtained for the n-type germanium samples with different conductivities and magnetic fields. </p> <p> An experimental verification of this theoretical analysis has been made with a 22.2 ohm-em, n-type germanium sample at 9.46 GHz. The applied transverse magnetic field was varied from 0 to 10 Kilogauss. Measurements of the reflection co efficients at the air-semiconductor interface for different values of the applied magnetic field have been made with a high precision microwave reflection bridge. The experimental results agree well with the theoretical results. </p> / Thesis / Master of Engineering (MEngr)

There has been a rapid growth of terrestrial and satellite communications in the last few decades of the 20th century. This has resulted in a heavy congestion of low microwave bands and has been a major driving force for exploring the upper microwave and millimeter-wave frequencies. One of the main requirements for a successful shift to the new frequency spectrum is the availability of high power solid-state transmitters. Solid-state devices such as diodes or transistors have been able to meet such demands when their output signals are combined using space-level power combining methods that avoid conduction losses, which become pronounced at millimeter wave frequencies. In this thesis, theoretical and experimental investigations are carried out into the spatial power combiners (SPCs) which employ active planar arrays formed by transistor amplifiers whose input and output ports are equipped with planar radiating elements. The SPC structures include the reflection-type combiner using the tile configuration of planar array and the transmission-type combiner using tile or tray configurations of planar arrays. The frequency bands chosen for the designing and testing of prototypes are X- and Ku-band. The first stage of the investigation concerns the 10 GHz reflection-type power combiner structure formed by a phased planar microstrip reflectarray (MRA) of 37-element dual-feed aperture coupled microstrip patch antennas equipped with open-circuit stubs as phasing components. The experimental tests reveal poor radiation performance and hence poor power combining efficiency of this structure. These results indicated the need for theoretical investigations into the operation of this type of SPC. The study of the unit cell of this power combiner reveals that the phase of an open-circuit stub does not increase linearly as a function of the stub length and its range is limited to less than (about is required for proper functioning). This finding, forms the basis for extending the investigations into alternative phasing mechanisms of a MRA which would offer a phasing range exceeding . A phasing mechanism exploiting variable size stacked patches is chosen. In order to accurately determine the phasing of the reflected wave, a theory based on an equivalent unit cell waveguide approach (WGA) is proposed and developed. The proposed theory is computationally efficient and is proven to be accurate compared with benchmark results published by other researchers. Following the verification, an offset feed 161-element two-layer printed MRA prototype with patches of variable size is designed and developed for operation in Ku-band. The test results aim at verifying the validity of applying a unit cell WGA to designing passive and active MRAs. The next investigations, which are presented in the thesis concern increasing operational bandwidth of the transmission-type SPC in tile configuration. The designs presented so far in the open literatures were based on edge-feed microstrip patch antennas as radiating elements of individual active stages and featured a narrow-band performance. In order to overcome this shortcoming, stacked patch (SP) microstrip antennas as receiving and transmitting elements in an active transmitarray (TXA) are proposed. For the aim of testing the proposed concept, a 16-element SP TXA is designed for operation in X-band. Two identical hard horn antennas with an approximately uniform field across the aperture for signal launching and collecting complete the design and development of this space-level power combiner. The performance of the developed device is assessed experimentally and an increased operational bandwidth is demonstrated. The final structure being investigated in the thesis project is the transmission-type SPC in tray configuration. This power combining structure employs a travelling wave antenna of uniplanar quasi-Yagi type as a radiating element to achieve broad-band operation. The investigated SPC is formed by seven trays of uniplanar quasi-Yagi antenna. In order to achieve uniform and in-phase excitation of individual trays, which is required to obtain high power combining efficiency, hard horn antennas and Schiffman phase shifters are employed in the design of this space-level combiner. The proposed device is developed and its performance is assessed through experiments. The work performed as part of this Ph.D. thesis project has resulted in 5 journal papers and 11 refereed conference papers. This acceptance rate supports the claim of the originality and significance of the research undertaken as part of the thesis project.

Presented in this thesis are the following theoretical investigations carried out on the non-invasive microwave hyperthermia of malignant tumours in the human body: Fundamental concepts of electromagnetic wave propagation through a biomass and its interaction with it, are discussed. Various types of applicators used for producing hyperthermia in a biomass, are also discussed. Propagation of a uniform plane electromagnetic wave through a human body is investigated for the general case of oblique incidence. Various models used for the human body have been discussed and the planar multilayer model has been chosen for this study. Reflection and transmission coefficients for both the parallel and perpendicular linear polarisations of the wave, have been determined. For normal incidence, power transfer ratio at the muscle has been defined and calculated at 433, 915 and 2450 MHz (ISM frequencies). Efects of skin thickness and also of fat thickness, on the power transfer ratio at muscle, have been studied. Effects of the thickness and dielectric constant of a bolus, and also of the dielectric constant of an initial layer, on the power transfer ratio, have been studied and their optimum values obtained at the ISM frequencies. For microwave hyperthermia, 915 MHz is recommended as the frequency of operation. Steady-state solution of the bioheat transfer equation has been obtained, assuming the biomass to be a semi-infinite homogeneous medium. Effects of various physical parameters on the temperature profile in the biomass, have been studied. Also studied is the effect of the surface temperature on the magnitude, location and the width of the temperature peak attained in the biomass. A method to determine the microwave power and the surface temperature required to produce a prescribed temperature profile in the biomass, has been developed. The transient-state solution of the bioheat transfer equation has been obtained to study the building up of the temperature profile. Procedures for the design of an open-ended rectangular metal waveguide applicator and for estimating the total microwave power requirement to produce hyperthermia in the human body, have been developed. Performance of the applicators employing linear as well as planar arrays of open-ended rectangular metal waveguide antennas, has also been studied. In order to reduce the overall physical size of the applicators, filling up of the feed waveguide with a high dielectric constant but low loss material is suggested. A simple method of obtaining the elements of the array by partitioning a large aperture by using metal walls has been adopted. Calculation of the total microwave power required by various applicators for producing hyperthermia at various depths in a biomas, have been made and a comparison of the performance of various applicators, has been presented.

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.

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.

This diploma thesis deals with the design and simulation of multi-layer stacked Yagi antenna at the frequency of 60 GHz. At work are proposed and compared two ways of antenna feeding methods. Based on the results obtained, antenna is fed by substrate integrated waveguide. The proposed antenna has been optimized in terms of gain and impedance matching at the specified frequency. The correct functionality of the antenna was verified by simulation program CST MWS 2011. Simulation results were verified experimentally.

This thesis presents research towards enabling micromachined millimeter and submillimeter wave focal plane arrays (FPAs). The FPAs operate under the following principle: a switch network consisting of microelectromechanical (MEMS) switches, integrated with micromachined waveguides, is used to feed an array of antenna elements, located in the focal plane of a high-gain quasi-optical system. Hence, it is possible to switch between a set of narrow beams in different directions. Such beam steering systems are needed for future millimeter and submillimeter wave imaging and communication systems. The contributions to future MEMS-switchable FPAs presented here are organized in three papers, as described below. Paper I presents a criterion on the spacing between adjacent FPA elements which results in -3 dB overlap between the switched beams, for the special case when an extended hemispherical dielectric lens is used as the optical system. A key step towards this criterion is a closed-form relation between the scan angle and the FPA element's position, which results in an expression for the effective focal length of extended hemispherical lenses. A comparison with full-wave simulations demonstrates an excellent agreement with the presented theoretical results. Finally, it is shown that the maximum feasible FPA spacing when using an extended hemispherical lens is about 0.7 wavelengths. Paper II presents a numerical study of silicon-micromachined planar extended hemispherical lenses, with up to three matching regions used to reduce internal reflections. The effective permittivity of the matching regions is tailor-made by etching periodic holes in the silicon wafer. The optimal thickness and permittivity of the matching regions were determined using TRF optimization, in order to yield the maximum wide-band aperture efficiency and small side-lobes. We introduce a new matching region geometry, referred to as shifted-type matching regions, and it is demonstrated that using three shifted-type matching regions results in twice as large aperture efficiency as compared to using three conventional concentric-type matching regions. Paper III presents a submillimeter-wave single-pole single-throw (SPST) 500-750 GHz MEMS waveguide switch, based on a MEMS-reconfigurable surface inserted between two waveguide flanges. A detailed design parameter study is carried out to select the best combination of the number of horizontal bars and vertical columns of the MEMS-reconfigurable surface, for achieving a low insertion loss in the transmissive state and a high isolation in the blocking state. A method is presented to model the non-ideal electrical contacts between the vertical cantilevers of the MEMS surface, with an excellent agreement between the simulated and measured isolation. It is shown that the isolation can be improved by replacing an ohmic contact by a new, capacitive contact. The measured isolation of the switch prototype is better than 19 dB and the measured insertion loss is between 2.5 and 3 dB. / Denna avhandling presenterar forskning som syftar till att möjliggöra fokalplans-gruppantenner (FPAs) för våglängder i millimeter och submillimeterområdet. Principen för en sådan FPAs funktion är följande: ett nätverk bestående av mikroelektromekaniska (MEMS) switchar, används för att välja mellan de olika antenn-elementen i en gruppantenn, som placerats i fokalplanet av ett optiskt system. Därmed blir det möjligt att välja från en uppsättning av smala lober i olika riktningar. Sådana lob-styrningssystem behövs för framtida radar- och kommunikationssystem i millimeter och submillimeterområdet. Resultaten är uppdelade i tre vetenskapliga artiklar, som beskrivs nedan. I den första artikeln (Paper I) presenteras ett villkor för avståndet mellan närliggande FPA-element som resulterar i -3 dB överlappning mellan de switchade loberna, för specialfallet då en förlängd hemisfärisk lins används som optiskt system. Det viktigaste steget mot att hitta detta villkor är att bestämma en analytisk relation mellan avsökningsvinkeln och FPA-elementens position. Detta resulterar i ett uttryck för den effektiva fokallängden för denna typ av lins. En utmärkt överensstämelse har funnits mellan dessa relationer och simuleringar. Slutligen visas det att de största möjliga FPA-avstånden för en förlängd hemisfärisk lins är ungefär 0.7 våglängder, vilket uppnås för linser med låg permittivitet. I den andra artikeln (Paper II) presenteras en numerisk studie av plana förlängda hemisfäriska linser, som kan produceras från en kiselskiva. Linserna har upp till tre matchningsregioner, som används för att reducera interna reflektioner. Den effektiva permittiviteten av de matchande regionerna skräddarsys genom etsning av periodiska hål i kiselskivan. Den optimala tjockleken och permittiviteten av de matchande regionerna har bestämts med hjälp av TRF-optimering, för att ge maximal bredbandig direktivitet och minimala sidlober. En ny geometri introduceras för matchningsregionerna, som vi kallar matchningsregioner av skiftad typ. Vi visar att användning av tre matchningsregioner av skiftad typ resulterar i en dubbelt så hög apertur-effektivitet, jämfört med att använda tre konventionella matchningsregioner av koncentrisk typ. I den tredje artikeln (Paper III) presenteras en MEMS-switch för rektangulära vågledare, för frekvensområdet 500-750 GHz. Baserat på en designparameterstudie har den bästa kombinationen av antalet horisontella rader och vertikala kolumner hos den MEMS-konfigurerbara ytan valts ut, för att uppnå låga förluster i det öppna tillståndet och hög isolation i det blockerande tillståndet. I artikeln presenteras en metod för att modellera icke-perfekta elektriska kontakter mellan de fixerade och de rörliga delarna i MEMS-ytan. Denna metod uppvisar en utmärkt överensstämmelse mellan den simulerade och den uppmätta isolationen. Vi visara att isolationen kan förbättras med hjälp av en ny typ av kapacitiv kontakt. Den uppmätta isolationen hos den presenterade switch-prototypen är högre än 19 dB, och den uppmätta förlusten är mellan 2.5 och 3 dB. / <p>QC 20161206</p>

Para abordar el análisis de estas estructuras de forma altamente eficiente, se pretenden utilizar dos enfoques distintos, que llevarían a dos técnicas distintas y eficientes, pero cada una de ellas con sus ventajas e inconvenientes respecto de la otra, que podremos concluir una vez finalizado el trabajo de investigación. Por un lado, se pretende utilizar el Método de los Momentos, una técnica numérica que convierte las ecuaciones integrales de un problema electromagnético en un sistema linear, expandiendo la magnitud desconocida usando un conjunto de funciones con coeficientes desconocidos. Al forzar las condiciones de contorno, en este caso de potencial eléctrico, en un determinado número de puntos, se obtiene un sistema linear de ecuaciones que será resuelto numéricamente. Por otro lado, según el segundo enfoque, pretende utilizar una expansión en modos cilíndricos del campo, tanto incidente como dispersado. Dada la geometría circular de las vías éstas pueden ser caracterizadas de forma analítica mediante espectros circulares. Posteriormente se resolverá el acoplo entre las vías mediante el método de [1] pero generalizado al caso de objetos inmersos en un medio dieléctrico infinito, y se desarrollará un nuevo método de acoplo modal entre modos cilíndricos y modos guiados proyectando las ecuaciones del acoplo modal tanto sobre modos cilíndricos como sobre modos guiados para evitar las singularidades que aparecen con el método de de [2] cuando los planos de referencia están muy próximos al objeto dispersor. Por tanto, esta técnica caracterizará las vías de forma analítica y resolverá las integrales del acoplo de modos mediante la transformada rápida de Fourier. Para aumentar más aún la eficiencia de ambos métodos se evitará repetir los cálculos para cada punto en frecuencia, y se implementará la técnica de barrido rápido en frecuencia similar descrita en [3], adaptándola al caso particular de cada método de análisis, aunque se prevé que quizá dicho procedimiento sea más difícil de implementar en el segundo método. Se espera que ambas técnicas puedan proporcionar unos tiempos de computación inferiores a los del software comercial de análisis electromagnético más habitual (i.e. HFSS), y también inferiores a otros métodos de análisis recientemente aparecidos en la bibliografía técnica ([4],[5],[6]). En concreto, se espera que los tiempos de computación para barrido discreto en frecuencia sea inferior con el segundo método ya que usa únicamente expresiones analíticas y transformada rápida de Fourier, pero, dado que el primer método es más susceptible de realizar barrido rápido en frecuencia, éste puede ser muy útil a la hora de realizar muchos análisis consecutivos. Una vez se disponga de métodos eficientes para el análisis de dispositivos SIW, se abordará el diseño de varios dispositivos pasivos en esta tecnología (filtros de diferentes topologías, diplexores, multiplexores, híbridos, acopladores, etc.). Como se dispone de una vasta experiencia en el grupo de investigación en el diseño de dispositivos en guía de onda rectangular, se puede como primera aproximación realizar el diseño en guía, y luego transformar esta estructura guiada en otra en tecnología SIW mediante unas reglas empíricas que relacionan ambas tecnologías [7]. Posteriormente se debe ajustar el diseño en el dispositivo SIW ya que estas reglas empíricas no consiguen que la respuesta sea idéntica a la del dispositivo guiado original, principalmente debido al hecho de que los irises rectangulares de la guía son transformados en vías metalizadas con geometría circular, no rectangular. Para minimizar este ajuste, se diseñará el dispositivo guiado con irises con esquinas redondeadas en la cavidad (método de [8] pero con un simulador más eficiente [9]), haciendo que el radio de esas esquinas redondeadas coincida con el de las vías metalizadas que se van a utilizar en el dispositivo SIW. Esto permitirá [...] (Ver documento anexo) / Díaz Caballero, E. (2013). Efficient analysis and design of devices in Substrate Integrated Waveguide (SIW) technology [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/34627