In recent years, multiferroics was one of the most popular materials and were widely studied by many scientists. Among all we interested the most is BiFeO3, which exist a room temperature ferromagnetic and ferroelectric properties with high ferromagnetic transition temperature Tc that can provide various kind of applications. However, the drawback of the BiFeO3 is difficult to synthesize the pure phase and to eliminate the leakage of the current. According to others¡¦ reports, with a proper doping can reduce the evaporation of Bi atoms and stabilize the crystal structure. Therefore, we choose Pb as the mixed elements and wish to reduce the unstable oxygen vacancies around the Bi atoms and to increase the dielectric property of Bi1-xPbxFeO3. In our experiment, SrRuO3 is chosen as the buffer layer material, which can grow as a strain relaxed film on the substrate. It is found that the strain relaxation transforms the SrRuO3 crystal structure to a nearly cubic one which has a lattice matching with Bi1-xPbxFeO3. As a result of this, we might improve the leakage problems of Bi1-xPbxFeO3.

Cette thèse traite de la conception de systèmes électromécaniques, en particulier des machines électriques dédiées à des applications de traction. La démarche adoptée allie précision des résultats et réduction du temps de calcul du processus. A cet égard, deux thèmes ont été abordés dans cette thèse. Le premier thème concerne la modélisation de machines électriques et l’utilisation de méthodes semi-numériques. Une architecture de réseau de réluctances est proposée pour analyser les performances de machines à flux axial. Elle permet la prise en compte de l'aspect temporel et la caractéristique non-linéaire des matériaux ferromagnétiques. Des modèles basés sur la méthode des éléments finis ont été établis pour valider les résultats de modélisation. Le faible écart entre modèles numériques et semi-numériques montre le bien fondé des méthodes proposées. Des dimensionnements offrant un compromis entre précision de la solution finale et temps de calcul font l’objet du second thème de la thèse. La technique du Space Mapping est connue pour son efficacité, elle permet d'exploiter à moindre coût un modèle précis. Deux techniques qui en dérivent sont proposées en associant la modélisation par réseau de réluctances et des techniques d'optimisation. La première repose sur la modélisation de l'erreur entre des modèles de précisions différentes par une fonction à bases radiales. La deuxième intègre la correction de l'erreur dans la résolution des réseaux de réluctances en couplant les modèles linéaire et non-linéaire d'une machine électrique. / This thesis proposes contributions in design methodologies for electromechanical systems, in particularly electrical machines. The proposed strategy allies precision and reduction in simulation time. Thus, two themes were studied. The first theme concerns electromagnetic modeling by means of semi-numerical models. Reluctance’s network topology is proposed in order to analyze performances of permanent magnet axial flux machines. It can take into account the temporal aspect and the non-linearity of ferromagnetic materials. Finite element models were established in order to compare and validate the proposed modeling strategy. Thus, the small error between models (less than 5%) shows the efficiency of the models. Sizing based on optimization techniques, offering a compromise between final solution and computation time, are treated in the second theme of this thesis. Space Mapping is known as an efficient optimization technique, which enables exploiting costly models without being prohibited by computation time. Two derived techniques are proposed and applied to design the axial flux machines. The first, proposes the modeling of the error between models with different precision through radial basis function. The second embeds error correction in the magnetic equivalent circuit resolution in order to couple linear and non-linear models of an electrical machine.

Ce mémoire est centré sur l’application de la technique d’optimisation de type Space Mapping dans le cadre du dimensionnement d’actionneurs électriques pris en compte par des modélisations multi-physiques. L’intérêt particulièrement recherché de ce type de méthode est la réduction potentiellement forte du coût du dimensionnement optimal. Cette volonté de réduction du coût de l’approche optimale s’explique par plusieurs considérations. En premier lieu, la modélisation des actionneurs tend à considérer de plus en plus de phénomènes physiques (tels que les phénomènes magnétiques, électriques, thermiques, mécaniques …) afin de décrire au mieux les phénomènes observés et mesurés. En second lieu il devient alors nécessaire de tenir compte des couplages entre ces physiques afin de traduire au plus juste l’interdépendance de ces phénomènes. Dans ce cadre, un travail particulier a été réalisé concernant la prise en compte des aspects thermiques dans les machines électriques. C’est ainsi qu’un modèle thermique à constantes localisées d’une machine synchrone à aimants permanents a été construit. Pour valider les résultats de calcul et préciser la définition de certain de ses éléments, une démarche expérimentale a été réalisée. Tous ces points, traduits dans le plan numérique, haussent le coût de l’évaluation des performances des actionneurs, et donc celui de leurs dimensionnements. De là, l’utilisation des techniques d’optimisation basées sur des modèles substituts permet d’envisager des réductions significatives des coûts de dimensionnement. La technique de Space Mapping est utilisée dans ce travail comme solution pour trouver un compromis entre la qualité des solutions trouvées et le temps de calcul. Plus particulièrement, elle est utilisée pour résoudre un problème de dimensionnement optimal d’une machine synchrone à aimants permanents assurant la fonction de démarreur dans une application de véhicule hybride. L’approche d’optimisation par Space Mapping a été comparée à celle, plus classique, n’utilisant qu’une seule modélisation de l’actionneur à dimensionner, c’est-à-dire sans modèle substitut. Il est montré que les techniques de Space Mapping sont à même de trouver des solutions de dimensionnement similaires à celles issues d’une approche classique, mais de manière beaucoup plus efficace, i.e. en utilisant un nombre plus faible d’évaluations de la modélisation multi-physique de l’actionneur. / This thesis focuses on the application of the Space Mapping optimization technique in the case of the sizing of electrical actuators taking into account a multi-physical modeling. The main interest in this type of optimization method is to considerably reduce the cost of optimal sizing. The need to use such optimization approach is due to several considerations. First, electrical actuators modeling tends to increasingly require the consideration of several physical phenomena (such as magnetic, electrical thermal and mechanical phenomena) in order to better describe observed and measured phenomena. Besides, it becomes necessary to take into account couplings between the different physical phenomena to precisely calculate the interdependencies between these phenomena. In this context, taking into account the thermal aspect in the case of electrical machines is particularly highlighted. A lumped parameter model of a permanent magnet synchronous machine is built. An experimental procedure has been followed to validate calculation results and define some elements of the proposed model. When implemented numerically, all points mentioned above increase the cost of the calculation of the performances of the electrical actuator, and then the cost of the optimal sizing. Thus, the use of an optimization technique based on surrogate models permits to reduce the optimal sizing cost. Space Mapping technique was used in this work as a solution to find a compromise between the quality of the found results and the calculation time. It is particularly used to solve an optimal sizing problem of a permanent magnet synchronous machine used as starter in a hybrid vehicle application. The Space Mapping optimization approach was compared to a classical one using a unique modeling of sized the electrical actuator : no surrogate model is used in the classical approach. Il is demonstrated that the Space Mapping techniques find optimization results that are similar to those found by the classical approach, yet, in a much more efficiently. Space Mapping techniques require only few calculations of the multi-physical model of the actuator.

This thesis contributes to the development of tuning space mapping (TSM) for computer-aided design and optimization of microwave circuits. Tuning space mapping applies the traditional engineering tuning idea into the realm of space mapping. It takes advantage of both the efficiency of space mapping and the expertise required for tuning of engineering devices. We present the state of the art in tuning space mapping and selected applications, and discuss how it relates to regular space mapping. A TSM algorithm is illustrated and implemented. Tuning space mapping shifts the burden of optimization from expensive electromagnetic (EM) models to cheap and fast tuning models. Meanwhile, design accuracy is achieved by keeping the EM simulation result in an S-parameter file in the circuit simulator, while performing optimization only on certain circuit theory-based components that are introduced into the tuning model. One important step in this tuning approach is to translate the tuning parameters to adjustments in the design parameters. Up to now, this was implemented by experience. Scarcely any systematic algorithm was suggested. In this thesis, we introduce a systematic "calibration" process which aims at calibrating the EM dimensions by the optimizable tuning parameters. Several calibration methods can accomplish this translation process. They are demonstrated here by applications. / Thesis / Master of Applied Science (MASc)

<p> This thesis contributes to the development of adjoint variable methods (AVM) and space mapping (SM) technology for computer-aided electromagnetics (EM)-based modeling and design of microwave circuits and antennas.</p> <p> The AVM is known as an efficient approach to design sensitivity analysis for problems of high complexity. We propose a general self-adjoint approach to the sensitivity analysis of network parameters for an Method of Moments (MoM) solver. It requires neither an adjoint problem nor analytical system matrix derivatives. For the first time, we suggest practical and fast sensitivity solutions realized entirely outside the EM solver, which simplifies the implementation. We discuss: (1) features of commercial EM solvers which allow the user to compute network parameters and their sensitivities through a single full-wave simulation; (2) the accuracy of the computed derivatives; (3) the overhead of the sensitivity computation. Our approach is demonstrated by FEKO, which employs an MoM solver.</p> <p> One motivation for sensitivity analysis is gradient-based optimization. The sensitivity evaluation providing the Jacobian is a bottleneck of optimization with full-wave simulators. We propose an approach, which employs the self-adjoint sensitivity analysis of network parameters and Broyden's update for practical EM design optimization. The Broyden's update is carried out at the system matrix level, so that the computational overhead of the Jacobian is negligible while the accuracy is acceptable for optimization. To improve the robustness of the Broyden update in the sensitivity analysis, we propose a switching criterion between the Broyden and the finite-difference estimation of the system matrix derivatives.</p> <p> In the second part, we apply for the first time a space mapping technique to antenna design. We exploit a coarse mesh MoM solver as the coarse model and align it with the fine mesh MoM solution through space mapping. Two SM plans are employed: I. implicit SM and output SM, and II. input SM and output SM. A novel local meshing method is proposed to avoid inconsistencies in the coarse model. The proposed techniques are implemented through the new user-friendly SMF system. In a double annular ring antenna example, the S-parameter is optimized. The finite ground size effect for the MoM is efficiently solved by SM Plan I and the design specification is satisfied after only three iterations. In a patch antenna example, we optimize the impedance through both plans. Comparisons are made. Coarseness in the coarse model and its effect on the SM performance is also discussed.</p> / Thesis / Master of Applied Science (MASc)

<p> This thesis contributes to the computer-aided design (CAD) of spiral inductors and LC resonators with spiral inductors exploiting full-wave electromagnetic (EM) analysis.</p> <p> The spiral inductor is widely used in radio frequency integrated circuits (RF ICs), such as low noise amplifiers (LNA) and voltage controlled oscillators (VCO). The design of spiral inductors has a direct influence on the performance of these circuits. Recently proposed optimization methods for spiral inductors are usually based on circuit models, which are computationally efficient but inaccurate compared with full-wave electromagnetic (EM) simulations.</p> <p> For the first time, we develop an optimization technique for the design of spiral inductors and LC resonators exploiting both the computational efficiency of a (cheap) circuit model and the accuracy of a full-wave EM analysis, based on geometric programming (GP) and space mapping (SM). With the new technique, we can efficiently obtain EM-validated designs with considerable improvement over those obtained with traditional optimization methods.</p> / Thesis / Master of Applied Science (MASc)

[ES] El creciente número de dispositivos intercambiando datos ha empujado a las empresas del sector espacial a utilizar bandas de frecuencia cada vez más altas, como Ku, K y Ka, ya que permiten emplear canales de frecuencia más anchos. A medida que disminuye la longitud de onda, el tamaño de los filtros se reduce y, por tanto, son más sensibles a las desviaciones de fabricación. Para compensar estos errores, es necesario emplear elementos de sintonía en la etapa de diseño. En este contexto presentamos una estrategia de diseño que permite incluir todos los factores no ideales, como elementos de sintonía o esquinas redondeadas, en las simulaciones finales de filtros y multiplexores. Una vez se han fabricado los filtros es necesario ajustar manualmente los elementos de sintonía hasta recuperar la respuesta objetivo. Sin embargo, para realizar esta tarea con éxito es necesario tener mucha experiencia previa y, aún así, conlleva un tiempo considerable. Por tanto, también proponemos un procedimiento de sintonización eficiente y sistemático que permite a cualquier persona, independientemente de su experiencia previa en sintonización, realizar esta tarea con éxito. Además del aumento de las tasas de transmisión, otros desafíos del sector espacial son reducir el tamaño y peso de sus componentes, así como dotarlos de capacidad dereconfiguración. Emplear dispositivos multifunción como filtros multibanda o dispositivos reconfigurables es una posible solución. En este contexto, proponemos una nueva familia de filtros multibanda en guía de ondas que puede adaptarse a las futuras necesidades del sector espacial. Con el mismo objetivo, también proponemos una familia de dispositivos reconfigurables de varios estados discretos que pueden modificar su comportamiento de forma remota. / [CA] El creixent nombre de dispositius intercanviant dades ha empés a les empreses del sector espacial a utilitzar bandes de freqüència cada vegada més altes, com Ku, K i Ka, ja que permeten fer servir canals de freqüència més amples. A mesura que la longitud d'ona disminueix, la mida dels filtres es redueix i, per tant, són més sensibles a les desviacions de fabricació. Per compensar aquests errors, és necessari fer servir elements de sintonia en l'etapa de disseny. En aquest context presentem una estratègia de disseny que permet incloure tots els factors no ideals, com a elements de sintonia o cantonades arrodonides, en les simulacions finals de filtres i multiplexors. Una vegada s'han fabricat els filtres és necessari ajustar manualment els elements de sintonia fins a recuperar la resposta objectiu. Però, per realitzar aquesta tasca amb èxit és necessari tenir molta experiència prèvia i, així i tot, comporta un temps considerable. Per tant, també proposem un procediment de sintonització eficient i sistemàtic que permet a qualsevol persona, independentment de la seua experiència prèvia en sintonització, realitzar aquesta tasca amb èxit. A més de l'augment de les taxes de transmissió, altres desafiaments de el sector espacial són reduir la mida i pes dels seus components, així com dotar-los de capacitat de reconfiguració. Emprar dispositius multifunció com filtres multibanda o dispositius reconfigurables és una possible solució. En aquest context, proposem una nova família de filtres multibanda en guia d'ones que pot adaptar-se a les futures necessitats del sector espacial. Amb el mateix objectiu, també proposem una família de dispositius reconfigurables de diversos estats discrets que poden modificar el seu comportament de forma remota. / [EN] The need for ever increasing data rate of modern communication systems has motivated companies in the space sector to exploit higher frequency bands, such as Ku, K and Ka, in order to offer wider bandwidths to their customers. However, as the frequency increases, the wavelength decreases, and all waveguide hardware becomes smaller and more sensitive to deviations from the ideal dimensions that normally occur when manufacturing the devices. In order to compensate for these deviations (or errors), tuning elements must then be added to the hardware and included in the design process. In this context, therefore, we focus on the investigation of novel design strategies for filters and multiplexers with the objective of including all necessary non-ideal factors in the design process. It is important to note in this context that, once the filters are manufactured, the tuning elements are usually adjusted manually until the desired target performance has been achieved. However, successfully performing this task requires a considerable amount of time and very significant previous experience in tuning microwave filters. Consequently, an additional goal of our research work is to propose efficient and systematic tuning procedures so that anyone, regardless of their previous tuning experience, can successfully perform this difficult task. In addition to the increasing data rates, another current challenge of advanced communication systems is the ability to be reconfigured remotely to adjust to changes in costumer demands. The use of multi-function or reconfigurable devices is then an attractive possible solution. In this context, therefore, we also investigate new families of multi-band waveguide filters that can be used to accommodate several pass bands in the same filtering device. Furthermore, we also propose a new family of reconfigurable devices with several discrete states that can be easily controlled remotely. / Melgarejo Lermas, JC. (2021). Advanced Techniques for the Design and Optimization of Multi-Band and Reconfigurable Microwave Waveguide Filters [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/172728

Cette thèse traite de la conception de systèmes électromécaniques, en particulier des machines électriques dédiées à des applications de traction. La démarche adoptée allie précision des résultats et réduction du temps de calcul du processus. A cet égard, deux thèmes ont été abordés dans cette thèse. Le premier thème concerne la modélisation de machines électriques et l'utilisation de méthodes semi-numériques. Une architecture de réseau de réluctances est proposée pour analyser les performances de machines à flux axial. Elle permet la prise en compte de l'aspect temporel et la caractéristique non-linéaire des matériaux ferromagnétiques. Des modèles basés sur la méthode des éléments finis ont été établis pour valider les résultats de modélisation. Le faible écart entre modèles numériques et semi-numériques montre le bien fondé des méthodes proposées. Des dimensionnements offrant un compromis entre précision de la solution finale et temps de calcul font l'objet du second thème de la thèse. La technique du Space Mapping est connue pour son efficacité, elle permet d'exploiter à moindre coût un modèle précis. Deux techniques qui en dérivent sont proposées en associant la modélisation par réseau de réluctances et des techniques d'optimisation. La première repose sur la modélisation de l'erreur entre des modèles de précisions différentes par une fonction à bases radiales. La deuxième intègre la correction de l'erreur dans la résolution des réseaux de réluctances en couplant les modèles linéaire et non-linéaire d'une machine électrique.

<p>In this thesis, inverse problems related to microwave imaging and microwave component design are investigated. Our contribution in microwave imaging for breast tumor detection can be divided into two parts. In the first part, a vectorial 3D near-field microwave holography is proposed which is an improvement over the existing holography algorithms. In the second part, a simple and fast post-processing algorithm based on the principle of blind de-convolution is proposed for removing the integration effect of the antenna aperture. This allows for the data collected by the antennas to be used in 3D holography reconstruction. The blind deconvolution algorithm is a well-known algorithm in signal processing and our contribution here is its adaptation to microwave data processing.</p> <p>Second, a procedure for accelerating the space-mapping optimization process is presented. By exploiting both fine- and surrogate-model sensitivity information, a good mapping between the two model spaces is efficiently obtained. This results in a significant speed-up over direct gradient-based optimization of the original fine model and enhanced performance compared with other space-mapping approaches. Our approach utilizes commercially available software with adjoint-sensitivity analysis capabilities.</p> / Thesis / Master of Applied Science (MASc)

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The aggressive space mapping algorithm is used in this project for the optimisation of electromagnetic structures. This technique combines the use of fast, less accurate models with more time-consuming, high precision models in the optimisation of a design. MATLAB’s technical computing environment possesses powerful tools for optimisation as well as the graphical representation and mathematical post-processing of data. A software interface, which uses Visual Basic for Applications, is created between MATLAB and the electromagnetic solvers, CST Microwave Studio and μWave Wizard, that are used for the fine and coarse model calculations. The interface enables the direct interchange of data, which allows MATLAB to control the optimisation for the automation of the design process. The optimisation of a microwave coaxial resonator with input coupling is used to demonstrate the design environment. An accurate equivalent circuit model is available to describe the problem. The space mapping optimisation of this structure works well, with a significant improvement in the efficiency of the optimisation when compared to standard optimisation techniques. Multimode horn antennas are of interest for use as feeds in radio-astronomy telescope systems. The design of a stepped circular horn antenna in the space mapping design environment is presented. The horn’s radiation pattern is optimised for low cross-polarisation. This structure is much more complex to model than the resonator example. The generalised scattering matrix representation is used in the coarse model description. The far-fields are calculated from the aperture fields by means of the Fast Fourier Transform. Various tests confirm that the optimisation is steered in the right direction as long as the coarse model response follows the trend of the fine model response over the optimisation space. The presented design environment is a powerful tool for the automation of the design of electromagnetic structures. / AFRIKAANSE OPSOMMING: Die aggressiewe ruimte-afbeelding algoritme word in hierdie projek gebruik vir die optimering van elektromagnetiese strukture. Hierdie tegniek kombineer die gebruik van vinnige, minder akkurate modelle tesame met tydrowende hoë presisie modelle tydens die optimering van ’n ontwerp. MATLAB se tegniese verwerkingsomgewing beskik oor kragtige gereedskap vir optimering sowel as die grafiese voorstelling en wiskundige verwerking van data. ’n Sagteware koppelvlak, wat Visual Basic for Applications benut, word geskep tussen MATLAB en die elektromagnetiese oplossers, CST Microwave Studio en μWave Wizard, wat vir die fyn en growwe model berekeninge gebruik word. Hierdie koppelvlak maak die direkte uitruiling van data moontlik, wat MATLAB in staat stel om die optimering te beheer ten einde die ontwerpsproses te outomatiseer. Die optimering van ’n mikrogolf koaksiale resoneerder met intree koppeling word gebruik om die ontwerpsomgewing te demonstreer. ’n Akkurate ekwivalente stroombaanmodel is beskikbaar om die probleem mee te beskryf. Die ruimte-afbeelding optimering van hierdie struktuur werk goed en toon ’n aansienlike verbetering in die doeltreffendheid van die optimering wanneer dit met standaard optimeringstegnieke vergelyk word. Multimodus horingantennes is van belang in radio-astronomie, waar dit as voere vir teleskope gebruik word. Die ontwerp van ’n trapvormige, sirkelvormige horingantenne in die ruimte-afbeelding ontwerpsomgewing word aangebied. Die stralingspatroon van die horing word optimeer vir lae kruispolarisasie. Hierdie struktuur is heelwat meer ingewikkeld om te modelleer as die resoneerder voorbeeld. Die veralgemeende strooimatriks voorstelling word gebruik in die growwe model beskrywing. Die ver-velde word bereken vanaf die velde in die bek van die antenne, deur gebruik te maak van die Vinnige Fourier Transform. Verskeie toetse bevestig dat die optimering in die regte rigting gestuur word, solank as wat die growwe model se gedrag dié van die fyn model oor die optimeringsgebied navolg. Die ontwerpsomgewing wat hier aangebied word, is ’n kragtige stuk gereedskap vir die outomatisering van die ontwerp van elektromagnetiese strukture.