Thesis (PhD (Electrical and Electronic Engineering))--University of Stellenbosch. / ENGLISH ABSTRACT: This dissertation presents a synthesis method for broadband high-power absorptive microwave lters by cascading a wide stop-band wa e-iron lter with an absorptive harmonic pad. The classical image impedance synthesis methods for wa e-iron lters are updated to allow for non-uniform boss patterns, which enable control over both the stop-band attenuation and pass-band re ection of the lter. By optimising an accurate circuit model equivalent, computationally intensive numerical EM optimisation are avoided. The nonuniform wa e-iron lter achieves the same electrical speci cation as similar lters in literature, but in a smaller form factor. The prototype presented displays less than -21 dB in-band re ection over 8.5 - 10.5 GHz, with stop-band attenuation in excess of 50 dB over the harmonic bands 17 - 31.5 GHz and 30 dB over the 34 - 42 GHz. The prototype is designed to handling 4 kW peak power incident in the transmitted band, and is 130 mm in length. Minimal full-wave tuning is required post-synthesis, and good agreement is found between synthesised and measured responses. Additionally, a completely novel oblique wa e-iron boss pattern is proposed. For the absorptive harmonic pad, transversal broadwall slots in rectangular waveguide, coupling to an absorptive auxiliary guide, are investigated in the presence of standing wave surface current distributions. An accurate circuit model description of the cascaded structure is developed, and optimised to provide a required level of input match in the presence of an arbitrary re ective lter. Using numerical port parameter data of the wa eiron lter, a harmonic pad is developed that provides -12.5 dB input re ection match across the band 17 - 21 GHz with up to 1 kW peak incident power handling capability, yet is only 33 mm in length. Again, good agreement is found between synthesised and measured responses of the cascaded structure. / AFRIKAANSE OPSOMMING: Hierdie proefskrif stel 'n sintesetegniek voor vir wyeband, ho edrywing absorberende mikrogol lters deur 'n kaskade kombinasie van 'n verlieslose wafelyster lter met 'n wye stopband, en 'n absorberende harmoniekdemper. Die klassieke sintesemetodes vir wafelyster lters word aangepas om nie-uniforme tandpatrone toe te laat, wat beheer oor beide die lter se stopband attenuasie en deurlaatband weerkaatsing moontlik maak. Deur die optimering van 'n akkurate stroombaanmodel van die lter kan berekeningsintensiewe numeriese EM optimering vermy word. Die nieuniforme wafelyster lter behaal dieselfde spesi kasies as soortgelyke gepubliseerde lters, maar is meer kompak. Die vervaardigingsprototipe handhaaf minder as -21 dB intreeweerkaatsing oor die deurlaatband van 8.5 - 10.5 GHz, asook attenuasie van meer as 50 dB oor die stopband 17 - 31.5 GHz en 30 dB oor 34 - 42 GHz. Die prototipe is ontwerp om 4 kW intree kruindrywing te hanteer in die deurlaatband, en is 130 mm lank. Die metode vereis minimale verstellings tydens volgolf simulasie, en die meetresultate stem goed ooreen met die gesintetiseerde gedrag. 'n Nuwe skuinstandpatroon word ook voorgestel vir wafelyster lters. Vir die harmoniekdemper word transversale bre ewandgleuwe in reghoekige gol eier wat koppel na 'n absorberende newegol eier ondersoek in die teenwoordigheid van staandegolfpatrone in oppervlakstroom. 'n Akkurate stroombaanmodel van 'n gleufkaskade word ontwikkel, en geoptimeer om 'n vereiste intreeweerkaatsing te bewerkstellig in samewerking met 'n arbitr^ere weerkaatsende lter. Deur gebruik te maak van poortparameterdata van die wafelyster lter word 'n 33 mm lange hamoniekdemper ontwikkel wat 'n maksimum intreeweerkaatsing van -12.5 dB oor die band 17 - 21 GHz handhaaf vir kruindrywingsvlakke van tot 1 kW. Goeie ooreenstemming tussen gesintetiseerde en gemete resultate word weereens waargeneem vir die volledige saamgestelde struktuur.

Um navio de guerra é considerado uma plataforma complexa no que tange o projeto de sistemas de comunicação RF, uma vez que diversos desempenhos devem ser considerados para sua adequada integração à mesma. Dentre eles está o controle da interferência de radiofrequência conhecida como co-site interference, causada primariamente pela alta potência radiada de alguns sistemas emissores em relativa proximidade física entre antenas à sistemas receptores de considerável sensibilidade. É o caso do sistema de comunicação civil satelital Inmarsat FB e do receptor GPS civil marítimo, os quais são encontrados em diversos navios mercantes e de guerra e têm frequências de operação próximas. Logo, esta dissertação foca na modelagem e estudo da interferência de radiofrequência entre um emissor Inmarsat FB civil em 1627 MHz (perturbador) e um sistema receptor GPS marítimo (vítima) em 1575 MHz, com suas respectivas antenas em proximidade física a bordo de um submarino; neste estudo, o classe Los Angeles original SSN-688. Adicionalmente, este estudo projeta mitigações para controlar e prevenir tal interferência. A metodologia proposta consiste na determinação do \"caminho da interferência\" por meio de simulação eletromagnética 3D da isolação eletromagnética entre as antenas perturbadora e perturbada em diferentes hipóteses de alocação nos mastros do SSN-688; caracterização dos efeitos da RFI causados pelo sinal interferente na recepção do sinal desejado, utilizando modelo de circuito cabeça de RF de um receptor típico GPS marítimo em avançado simulador de circuitos incluindo suas respectivas não linearidades; e na proposta, projeto, e fabricação de mitigações adequadas: neste estudo pré-filtros de micro-ondas em tecnologia planar de microfita. O desempenho dos pré-filtros fabricados é comparado com a simulação e com os requisitos de projeto, de maneira a adequadamente mitigar e controlar a interferência. / A war ship is considered a complex environment when it comes to the design of RF communication systems, since several performances must be considered for their integration into the platform. Among them is the control of co-site interference, mainly caused by high power transmitters co-located with sensitive receivers on an antenna to antenna limited space environment, such as on a submarine. It is the case of civilian Inmarsat FB satellite communication and maritime GPS systems, which are both typically encountered on several war and merchant ships and share close frequency bands. Therefore, this dissertation focuses on modelling and studying the RF interference between a civilian Inmarsat FB emitter on 1627 MHz (culprit) and a GPS maritime receiving system on 1575 MHz (victim) on close antennas proximity onboard a submarine: in this study the US Navy retired Los Angeles SSN-688 original class. Additionally, it proposes design of mitigations to attenuate and prevent such interference. The proposed methodology consists on determining the \"interference path\" by 3D EM simulation of the electromagnetic decoupling between culprit and victim\'s antennas on different antenna placement hypothesis onboard the SSN-688\'s masts; estimating the RFI effects on a typical GPS front end receiver circuit model on advanced circuit simulator including its non-linearities; and on proposing, designing and fabricating adequate mitigations: in this study microwave pre-filters based on planar microstrip technology. The performance of the pre-filters fabricated is compared with the simulation and with the requirements in order to attenuate and mitigate as much as possible the detected RFI.

Bandpass microwave filters are often modeled as a set of coupled discrete and localized resonators. This model is adequate in the narrow-band case. It, however, fails to describe accurately compact structures where stray couplings can be strong. To address this problem, a new view is proposed in this thesis. Instead of basing the model on localized discrete resonances, we start by constructing a model that is based on the global resonances of the structure. These are the resonances that the ports see and emerge when the entire structure is treated as a single unit. The resulting circuit, the transversal circuit, is universal. It is valid for any coupled resonator filter. The circuit is used in optimization of compact and ultra wideband suspended stripline filters and excellent results were obtained. In order to relate the global-eigen modes model to the conventional model, the issue of representation of microwave filters is investigated in detail. It is shown that a microwave filter can be represented by an infinite number of similar coupling matrices by using different modes as basis. According to this new view, a similarity transformation in microwave coupled resonator filters is interpreted as a change of basis. Two circuits that are related by a similarity transformation represent the same filter structure by using different sets of modes as basis. These conclusions were exploited in establishing a design theory for filters with dual-mode cavities. The new theory leads to direct and accurate design techniques that need no, or minimal, optimization. No tuning is used in the CAD steps. Tuning may only be required to account for manufacturing tolerances. A new tuning configuration is described and validated by computer simulation. A novel dual-mode filter with improved quality factor and reduced sensitivity is developed and designed within the same approach. The filter is fabricated and measured and excellent results are achieved. The same design methodology was used to introduce a new class of dual-mode dual-band microwave filters with improved sensitivity. It is also shown that canonical dual-mode filters can be designed within the same view with minimal local optimization of the input cavity. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2010-03-31 01:33:36.818

El efecto multipactor de ruptura en RF ha sido objeto de numerosos estudios desde hace más de 80 años, a partir del desarrollo de los primeros aceleradores de partículas en la primera mitad del siglo XX. A mediados de ese siglo, con el desarrollo de fuentes de alta potencia para aplicaciones radar y la llegada de los satélites artificiales, la investigación del multipactor cobró una considerable relevancia, al convertirse este fenómeno en un riesgo determinante para costosos proyectos comerciales. Las guías de onda con secciones rectas canónicas, como las rectangulares o las coaxiales, han sido tradicionalmente las más utilizadas en dispositivos de microondas. Sus principales ventajas son que sus campos electromagnéticos pueden resolverse analíticamente, lo que permite su aplicación directa en diseños complejos, y la simplicidad de su fabricación. Pero las capacidades de computación y las prestaciones de los algoritmos se han multiplicado con los años, lo que ha permitido ampliar el espectro de posibles topologías a geometrías casi arbitrarias, ofreciendo al diseñador una mayor libertad creativa. En todo caso, gran parte de los dispositivos de microondas actuales siguen confiando en la madurez y fiabilidad de las tecnologías de guía de onda tradicionales, que no requieren una inversión adicional en equipos de fabricación. La supresión del efecto multipactor es la motivación para arriesgarse a probar topologías de guía de onda innovadoras, como la guía en forma de cuña. Es en este contexto donde este trabajo de doctorado pretende ofrecer una contribuci'on. En primer lugar, se ha desarrollado un modelo numérico para predecir el efecto multipactor de ruptura en guías de onda huecas en forma de cuña. Esta herramienta ha permitido la identificación de criterios óptimos de diseño. Así mismo, se ha adaptado un método de síntesis de filtros paso-banda en guía rectangular para poder realizar un diseño similar pero basado en la nueva topología. Como culminación, las estructuras diseñadas se han fabricado y medido, con el fin de comprobar sus prestaciones electromagnéticas y su sensibilidad al efecto multipactor. Se ha registrado además una patente para proteger estos nuevos filtros. En resumen, el trabajo ha abarcado el ciclo de actividades relacionadas con el desarrollo industrial completo de un dispositivo pasivo de microondas: investigación básica, análisis, diseño, fabricación y calificación con medidas en el laboratorio. Estas medidas han comprobado la mejora prevista en los umbrales de multipactor de los filtros de microondas con topología en forma de cu¿na, y han confirmado que pueden ofrecer respuestas en frecuencia similares a aquellas de filtros basados en una guía de onda rectangular equivalente. Las implicaciones de los resultados han sido evaluadas a fondo y resumidas en este documento. Como observación final, se ha intentado redactar esta investigación de manera que refleje el proceso natural de aprendizaje, mostrando los aciertos y errores experimentados en el camino, todos los cuales han conducido al resultado final. Este reto no hubiera sido posible sin el apoyo y compromiso de varios profesionales de diferentes centros de investigación e industrias europeas (Universidad Politécnica de Valencia, Universidad de Valencia, Agencia Espacial Europea, Thales Alenia Espacio Espa¿na, Technische Universit¿at Darmstadt, 'Ecole Polythecnique F'ed'erale de Lausanne, Tesat, Aurora Software and Testing y Val Space Consortium), a los cuales estoy agradecido. / The multipactor RF breakdown effect has been object of numerous studies for over 80 years, since the development of the first particle accelerators in the beginning of the 20th century. Around the middle of that century, with the development of high power sources for radar applications and with the emergence of the artificial satellites, a new impulse was given to the multipactor research, since it became a risk for expensive commercial projects. Traditionally, waveguides with canonical cross sections, like rectangular or coaxial ones, have been the building blocks of most microwave devices. Their main advantages are that their electromagnetic fields can be solved analytically, enabling their direct application in complex designs, as well as their manufacturing simplicity. But over the years the computation capabilities and algorithms have continuously evolved, which has broadened the spectrum of possible topologies to almost arbitrary geometries, offering the designer more room for creativity. However, most of the current microwave devices still trust on the mature canonical waveguide technologies, which do not require an additional investment in manufacturing equipment. The suppression of the multipactor effect is the motivation for considering an innovative waveguide topology, like the wedge-shaped waveguide. It is within this context where this PhD work aims to offer a contribution. On the one hand, a numerical model for predicting the multipactor breakdown effect in wedge-shaped hollow waveguides has been developed. This tool has aided in the derivation of optimised design criteria. On the other hand, a bandpass filter synthesis method for rectangular waveguide has been adapted in order to calculate a similar design based on the new topology. As a culmination, the designed structures have been manufactured and tested, in order to verify their electromagnetic performance and their multipactor sensibility. A patent was also filed to protect these new filters. In short, this work has comprised the cycle of activities related to the whole industrial development of a passive microwave device: basic research, analysis, design, manufacturing and qualification through testing. These measurements have verified the predicted improvement in the multipactor thresholds of microwave filters with wedge-shaped topology, and have confirmed that they can offer similar frequency responses to the equivalent rectangular waveguide ones. The implications of the results have been thoroughly evaluated and summarised in this document. As a final remark, this research document has been drafted to reflect the natural learning process, and to show the rights and wrongs experienced in the way, which all have led to the final result. Such an endeavour would not have been possible without the support and commitment of several professionals from different European research centres and industries (Universidad Polit'ecnica de Valencia, Universidad de Valencia, European Space Agency, Thales Alenia Espacio Spain, Technische Universit¿at Darmstadt, 'Ecole Polythecnique F'ed'erale de Lausanne, Tesat, Aurora Software and Testing and Val Space Consortium), for which I am grateful. / Hueso González, J. (2013). Analysis of wedge-shaped waveguides and design of multipactor-resistant microwave bandpass filters. Análisis de guías de onda en forma de cuña y diseño de filtros de microondas paso-banda resistentes al efecto multipactor [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/33750

[ES] La presente tesis doctoral tiene como objetivo fundamental desarrollar nuevas estructuras capacitivas de filtrado en guía de ondas rectangular que sean capaces de proporcionar mayores ancho de banda en la banda de paso y, al mismo tiempo, mejorar la respuesta fuera de banda. Estas nuevas estructuras guiadas han sido pensadas para ofrecer nuevas soluciones tecnológicas para los filtros de microondas de alta frecuencia, con una variedad de diferentes funciones de transferencia, abordando específicamente las necesidades de los futuros sistemas de telecomunicaciones para aplicaciones terrestres y espaciales. En este contexto, por lo tanto, discutimos en este documento el estudio, diseño y fabricación de varios tipos de filtros de microondas en guía de ondas rectangular que muestran una mejora significativa con respecto al estado del arte. Las soluciones que discutimos se obtienen introduciendo modificaciones simples en la estructura de los filtros de microondas clásicos. Varias técnicas que emplean iris híbridos, resonadores con salto de impedancia, configuración en escalera y uniones T en plano E con conexiones en cortocircuito o manifold, se utilizan con éxito para cumplir con las exigentes especificaciones de los futuros sistemas para aplicaciones terrestres y espaciales. Además, un desafío actual adicional al que se enfrentan todos los diseñadores de equipos y componentes de microondas es la necesidad de reducir tanto su tamaño físico como su masa (o peso). Para abordar este problema, discutimos en este documento el uso de aperturas resonantes en guías de ondas rectangulares, presentando una nueva familia de filtros que se pueden usar para implementar funciones complejas de transferencia de banda única y banda doble con una reducción significativa de tamaño y masa. En los siguientes capítulos de esta tesis doctoral, cada tema se analiza en detalle, incluyendo las formulaciones teóricas básicas, los procedimientos de diseño, los resultados de las simulaciones electromagnéticas de onda completa, las consideraciones de fabricación y el rendimiento medido de una serie de prototipos. En todos los casos se ha encontrado una excelente concordancia entre las mediciones y las simulaciones realizadas, validando así completamente tanto las estructuras novedosas propuestas como sus procedimientos de diseño. / [CA] La present tesi doctoral té com a objectiu fonamental el desenvolupament de noves estructures capacitives de filtrat en guia d'ones rectangular que siguen capaços de proporcionar major ample de banda en la banda de pas i millorar, al mateix temps, la resposta fora de banda. Aquestes noves estructures guiades han sigut pensades per a oferir noves solucions tecnològiques per a filtres de microones d'alta freqüència, amb una varietat de diferents funcions de transferència, abordant específicament les necessitats dels futurs sistemes de telecomunicacions per a aplicacions terrestres i espacials. En aquest context, per tant, discutim en aquest document l'estudi, disseny i fabricació de diversos tipus de filtres de microones en guia d'ones rectangular que mostren una millora significativa respecte a l'estat de l'art. Les solucions que discutim s'obtenen introduint modificacions simples en l'estructura dels filtres de microones clàssics. Diverses tècniques que fan ús d'iris híbrids, ressonadors amb salt d'impedància, configuració en escala i unions T en plànol E amb connexions en curtcircuit o col·lector, s'utilitzen amb èxit per a complir amb les exigents especificacions dels sistemes futurs per a aplicacions terrestres i espacials. A més, un desafiament actual addicional al qual s'enfronten tots els dissenyadors d'equips i components de microones és la necessitat de reduir tant la seua grandària física com la seua massa (o pes). Per a abordar aquest problema, discutim en aquest document l'ús d'obertures ressonants en guies d'ones rectangulars, presentant una nova família de filtres que es poden usar per a implementar funcions complexes de transferència de banda única i doble banda amb una reducció significativa de grandària i massa. En els següents capítols d'aquesta tesi doctoral, cada tema s'analitza detalladament, incloent les formulacions teòriques bàsiques, els procediments de disseny, els resultats de les simulacions electromagnètiques d'ona completa, les consideracions de fabricació i el rendiment mesurat d'una sèrie de prototips. En tots els casos s'ha trobat una excel·lent concordança entre el mesurament i les simulacions realitzades, validant així completament tant les estructures noves propostes com els seus procediments de disseny. / [EN] The main objective of this doctoral thesis is the development of new capacitive filtering structures in rectangular waveguide that are able to provide wide bandwidths in the pass-band and improve, at the same time, the out-of-band response. These new guided structures have been developed in order to offer new technological solutions for high-frequency microwave filters, with a variety of different transfer functions, addressing specifically the needs of future telecommunication systems for both ground and space applications. In this context, therefore, we discuss in this document the study, design and manufacture of several types of microwave filter in rectangular waveguide that show a significant improvement with respect to the state-of-the-art. The new solutions that we propose are obtained by introducing simple modifications in the structure of classic microwave filters. Several techniques based on hybrid irises, stepped impedance resonators, staircase configuration and E-plane T-junctions with shorted stubs or manifold connections, are successfully used in order to meet the very demanding specifications of future systems for both ground and space applications. Furthermore, an additional current challenge faced by all designers of microwave components is the need to reduce both their physical size and mass (or weight). To address this issue, we discuss in this document the use of resonant apertures in rectangular waveguide, introducing a new family of filters which can be used to implement complex single and dual-band transfer functions with significant size and mass reduction. In the following chapters of this doctoral thesis, each subject is discussed in detail including the basic theoretical formulations, design procedures, the results of full-wave electromagnetic simulations, manufacturing considerations, and the measured performance of a number of prototypes. Excellent agreement is found in all cases between measurement and simulations, thereby fully validating both the novel structures discussed and their design procedures. / Valencia Sullca, JF. (2021). New Wide-Band Capacitive Filter Structures in Rectangular Waveguide Technology With Enhanced Out-of-Band Response [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/180198