The absence of appropriate media to cultivate photons efficiently at the micro or nano scale has hindered taking the full advantage of processing information with light. The proposal of such a medium for light, known as photonic crystals (PCs)--multi-dimensional artificially periodic dielectric media--brings the possibility of a revolution in communications and sensing much closer. In such media, one can manipulate light at a scale on the order of the wavelength or even shorter. Applications of PCs other than in communication include bio-sensing because of the peculiar properties of PCs such as the capability of enhance field-matter interaction and control over the group velocity. As a result, PC waveguide (PCW) structures are of interest and it is expected that PC sensors offer the feasibility of multi-analyte and compact sensing schemes as well as the ability of the detection of small absolute analyte quantities (nanoliters) and low-concentration samples (picomoles), which may be advantages over conventional approaches such as fiber optic and slab waveguide sensors. Depending on the nature of the analyte, either dispersive or absorptive sensing schemes may be implemented. Light propagation is controlled fully only with 3D PCs. One of the problems arising due to reducing the dimension to 2D is that PCs become strongly polarization sensitive. In many cases, one wants to implement polarization insensitive devices such that the PC provides a full band gap for all polarizations. To address this problem, a novel type of PC called annular PC is proposed and analyzed. The capability of tuning the TE and TM polarizations independently within the same structure provides great flexibility to produce polarization-independent or polarization-dependent devices as desired. PCW bends are expected to be the essential building blocks of photonic integrated circuits. Sharp corners having small radii of curvature can be obtained. To enhance the low-loss and narrow-band transmission through these bends, PC heterostructures waveguide concept is introduced. We show that in PCWs formed by joining different types of PCs in a single structure, light can flow around extremely sharp bends in ways that are not possible using conventional PCWs based on a single type of PC.

Disertacijoje sprendžiama lėtinimo sistemų kraštinių ir galinių laidininkų įtakos modelių tikslumui įvertinimo problema. Pagrindiniai tyrimo objektai – daugialaidžių ir meandrinių mikrojuostelinių linijų matematiniai modeliai, skaitiniai analizės metodai. Darbo tikslas – sukūrus modelius, grįstus baigtinių skirtumų laiko srities metodu, ištirti galinių ir kraštinių laidininkų netolygumų įtaką meandrinių mikrojuostelinių vėlinimo linijų laiko ir dažninėms charakteristikoms, pasiūlyti meandrinių vėlinimo linijų konstrukcijų tobulinimo priemones. Darbe sprendžiami uždaviniai: matematinių pavienės, susietųjų ir daugialaidžių mikrojuostelinių linijų modelių sudarymas ir savybių tyrimas, taikant baigtinių skirtumų bei baigtinių skirtumų laiko srities analizės metodus; daugialaidžių mikrojuostelinių linijų sintezės ir meandrinių mikrojuostelinių vėlinimo linijų analizės algoritmų bei jų elektrinių charakteristikų skaičiavimo metodikų sudarymas. Disertaciją sudaro įvadas, keturi skyriai, bendrosios išvados, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai. Įvadiniame skyriuje formuluojama tiriamoji problema, aptariamas darbo aktualumas, aprašomas tyrimų objektas, formuluojamas darbo tikslas bei uždaviniai, aprašoma tyrimų metodika, darbo mokslinis naujumas, rezultatų praktinė reikšmė, ginamieji teiginiai. Įvado pabaigoje pristatomi pranešimai konferencijose disertacijos tema bei pateikiama disertacijos struktūra. Pirmajame skyriuje pateikiama literatūros... [toliau žr. visą tekstą] / There are investigated accuracy issues of edges and ends evaluation problems of meander slow-wave systems in the dissertation. Objects of research – mathematical models of multiconductor and meander microstrip delay lines, numerical analysis methods. Aim of the work – after creating mathematical models, based on finite difference time domain method, explore ends and edges discontinuity effects on meander microstrip delay lines time and frequency characteristics, propose structural improvement measures of meander delay line. The dissertation approaches major tasks such as: mathematical individual, coupled, multiconductor microstrip lines models composition for performance and their properties investigation using finite difference and finite difference time domain methods of analysis; synthesis algorithm of multiconductor microstrip lines and analysis algorithm of meander microstrip delay line and methodology of their electrical characteristics calculation creation. The thesis consists of four parts including introduction, 4 chapters, conclusions, references. The introduction reveals investigated problem, importance of the thesis and object of research. It also describes the purpose and tasks of the dissertation, research methodology, scientific novelty and the practical significance of results examined in the thesis and defended statements. The introduction ends in presenting the author’s publications on the subject of the defended dissertation, offering the material of made... [to full text]

Power distribution networks (PDNs) are conducting structures employed in semiconductor systems with the aim of providing circuits with reliable and constant operating voltage. This network has non-neglible electrical parasitics. Consequently, when digital circuits inside the chip switch, the supply voltage delivered to them does not remain ideal and exhibits spatial and temporal voltage fluctuations. These fluctuations in the supply voltage, known as the power-supply noise (PSN), can affect the functionality and the performance of modern microprocessors. The design of this PDN in the chip is an important part in ensuring power integrity. Modeling and simulation of the PSN in on-chip PDNs is important to reduce the cost of processors. These PDNs have irregular geometries, which affect the PSN. As a result, they have to be modeled. The problem sizes encountered in this simulation are usually large (on the order of millions), necessitating computationally efficient simulation approaches. Existing approaches for this simulation do not guarantee at least one of the following three required properties: computationally efficiency, accuracy, and numerically robustness. Therefore, there is a need to develop accurate, numerically robust, and efficient algorithms for this simulation. For many interconnects (e.g., transmission lines, board connectors, package PDNs), only their frequency responses and SPICE circuits (e.g., nonlinear switching drivers, equivalent circuits of interconnects) terminating them are known. These frequency responses are usually available only up to a certain maximum frequency. Simulating the electrical behavior of these systems is important for the reliable design of microprocessors and for their faster time-to-market. Because terminations can be nonlinear, a transient simulation is required. There is a need for a transient simulation of band-limited frequency-domain data characterizing a multiport passive system with SPICE circuits. The number of ports can be large (greater than or equal to 100 ports). In this simulation, unlike in traditional circuit simulators, normal properties like stability and causality of transient results are not automatically met and have to be ensured. Existing techniques for this simulation do not guarantee at least one of the following three required properties: computationally efficiency for a large number of ports, causality, and accuracy. Therefore, there is a need to develop accurate and efficient time-domain techniques for this simulation that also ensure causality. The objectives of this Ph.D. research are twofold: 1) To develop accurate, numerically robust, and computationally efficient time-domain algorithms to compute PSN in on-chip PDNs with irregular geometries. 2) To develop accurate and computationally efficient time-domain algorithms for the causal cosimulation of band-limited frequency-domain data with SPICE circuits.

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The aim of this thesis was to make a practical tool for low frequency analysis in room acoustics.The need arises from Acad’s experience that their results from simulations using raytracing software deviate in the lower frequencies when compared to field measurements inrooms. The tool was programmed in Matlab and utilizes the Finite Difference Time Domain (FDTD) method, which is a form of rapid finite element analysis in the time domain.A number of tests have been made to investigate the practical limitations of the FDTD method, such as numerical errors caused by sound sources, discretization and simulation time. Boundary conditions, with and without frequency dependence, have been analysed bycomparing results from simulations of a virtual impedance tube and reverberation room to analytical solutions. These tests show that the use of the FDTD method appears well suited for the purpose of the tool.A field test was made to verify that the tool enables easy and relatively quick simulations of real rooms, with results well in line with measured acoustic parameters. Comparisons of the results from using the FDTD method, ray-tracing and finite elements (FEM) showed goodcorrelation. This indicates that the deviations Acad experience between simulated results and field measurements are most likely caused by uncertainties in the sound absorption data used for low frequencies rather than by limitations in the ray-tracing software. The FDTDtool might still come in handy for more complex models, where edge diffraction is a more important factor, or simply as a means for a “second opinion” to ray-tracing - in general FEM is too time consuming a method to be used on a daily basis.Auxiliary tools made for importing models, providing output data in the of room acoustic parameters, graphs and audio files are not covered in detail here, as these lay outside the scope of this thesis. / Målet för detta examensarbete var att undersöka möjligheten att programmera ett praktisktanvändbart verktyg för lågfrekvensanalys inom rumsakustik. Behovet uppstår från Acadserfarenhet att resultat från simuleringar med hjälp av strålgångsmjukvara avviker i lågfrekvensområdeti jämförelse med fältmätningar i färdigställda rum. Verktyget är programmerati Matlab och använder Finite Difference Time Domain (FDTD) metoden, vilket är en typav snabb finita elementanalys i tidsdomänen.En rad tester har genomförts för att se metodens praktiska begräsningar orsakade av numeriskafel vid val av ljudkälla, diskretisering och simuleringstid. Randvillkor, med och utanfrekvensberoende, har analyserats genom jämförelser av simulerade resultat i virtuella impedansröroch efterklangsrum mot analytiska beräkningar. Testerna visar att FDTD-metodentycks fungerar väl för verktygets tilltänkta användningsområde.Ett fälttest genomfördes för att verifiera att det med verktyget är möjligt att enkelt och relativtsnabbt simulera resultat som väl matcher uppmätta rumsakustiska parametrar. Jämförelsermellan FDTD-metoden och resultat beräknade med strålgångsanalys och finita elementmetoden(FEM) visade även på god korrelation. Detta indikerar att de avvikelser Acaderfar mellan simulerade resultat och fältmätningar troligen orsakas av osäkerheter i den ingåendeljudabsorptionsdata som används för låga frekvenser, snarare än av begränsningar istrålgångsmjukvaran. Verktyget kan fortfarande komma till användning för mer komplexamodeller, där kantdiffraktion är en viktigare faktor, eller helt enkelt som ett sätt att få ett”andra utlåtande” till resultaten från strålgångsmjukvaran då FEM-analys generellt är en förtidskrävande metod för att användas på daglig basis.Kringverktyg skapade för t.ex. import av modeller, utdata i form av rumsakustiska parametrar,grafer och ljudfiler redovisas inte i detalj i denna rapport eftersom dessa ligger utanförexamensarbetet.

The dispersion property of periodic structures is a hot research topic in the last decade. By exploiting dispersion properties, one can manipulate the propagation of electromagnetic waves, and produce effects that do not exist in conventional materials. This thesis is devoted to two important dispersion effects: negative refraction and designed surface plasmons. First, we introduce negative refraction and designed surface plasmons, including a historical perspective, main areas for applications and current trends. Several numerical methods are implemented to analyze electromagnetic effects. We apply the layer-KKR method to calculate the electromagnetic wave through a slab of photonic crystals. By implementing the refraction matrix for semi-infinite photonic crystals, the layer-KKR method is modified to compute the coupling coefficient between plane waves and Bloch modes in photonic crystals. The plane wave method is applied to obtain the band structure and the equal-frequency contours in two-dimensional regular photonic crystals. The finite-difference time-domain method is widely used in our works, but we briefly discuss two calculation recipes in this thesis: how to deal with the surface termination of a perfect conductor and how to calculate the frequency response of high-Q cavities more efficiently using the Pad\`{e} approximation method. We discuss a photonic crystal that exhibits negative refraction characterized by an effective negative index, and systematically analyze the coupling coefficients between plane waves in air and Bloch waves in the photonic crystal. We find and explain that the coupling coefficients are strong-angularly dependent. We first propose an open-cavity structure formed by a negative-refraction photonic crystal. To illuminate the physical mechanism of the subwavelength imaging, we analyze both intensity and phase spectrum of the transmission through a slab of photonic crystals with all-angle negative refraction. It is shown that the focusing properties of the photonic crystal slab are mainly due to the negative refraction effect, rather than the self-collimation effect. As to designed surface plasmons, we design a structured perfectly conducting surface to achieve the negative refraction of surface waves. By the average field method, we obtain the effective permittivity and permeability of a perfectly conducting surface drilled with one-dimensional periodic rectangle holes, and propose this structure as a designed surface plasmon waveguide. By the analogy between designed surface plasmons and surface plasmon polaritons, we show that two different resonances contribute to the enhanced transmission through a metallic film with an array of subwavelength holes, and explain that the shape effect is attributed to localized waveguide resonances. / QC 20100817

Les travaux présentés dans ce mémoire s’inscrivent dans la thématique de la transmission d’énergie sans fil, appliquée à l’alimentation à distance de capteurs, de réseaux de capteurs et d’actionneurs à faible consommation. Cette étude porte sur la conception,l’optimisation, la réalisation et la mesure de circuits Rectennas (Rectifying antennas)compacts, à faible coût et à haut rendement de conversion RF-DC.Un outil d’analyse globale, basé sur la méthode des Différences Finies dans le Domaine Temporel (FDTD), a été développé et utilisé pour prédire avec précision la sortie DC des rectennas étudiées. Les résultats numériques obtenus se sont avérés plus précis et plus complets que ceux de simulations à base d’outils commerciaux. La diode Schottky a été rigoureusement modélisée, en tenant compte de ses éléments parasites et de son boîtier SOT23, et introduite dans le calcul itératif FDTD.Trois rectennas innovantes, en technologie micro-ruban, ont été développées,optimisées et caractérisées expérimentalement. Elles fonctionnent à 2.45 GHz et elles ne contiennent ni filtre d’entrée HF ni vias de retour à la masse. Des rendements supérieurs à 80% ont pu être mesurés avec une densité surfacique de puissance de l’ordre de 0.21 mW/cm²(E = 28 V/m). Une tension DC de 3.1 V a été mesurée aux bornes d’une charge optimale de1.05 k_, lorsque le niveau du champ électrique est égal à 34 V/m (0.31 mW/cm²).Des réseaux de rectennas connectées en série et en parallèle ont été développés. Les tensions et les puissances DC ont été doublées et quadruplées à l’aide de deux et de quatre éléments, respectivement. / The work presented in this thesis is included within the theme of wireless power transmission, applied to wireless powering of sensors, sensor nodes and actuators with low consumption. This study deals with the design, optimization, fabrication and experimental characterization of compact, low cost and efficient Rectennas (Rectifying antennas).A global analysis tool, based on the Finite Difference Time Domain method (FDTD),has been developed and used to predict with a good precision the DC output of studied rectennas. The packaged Schottky diode has been rigorously modeled, taking into account the parasitic elements, and included in the iterative FDTD calculation.Three new rectennas, with microstrip technology, have been developed and measured.They operate at 2.45 GHz and they don’t need neither input HF filter nor via hole connections. Efficiencies more than 80 % have been measured when the power density is 0.21mW/cm² (E = 28 V/m). An output DC voltage of about 3.1 V has been measured with anoptimal load of 1.05 k_, when the power density is equal to 0.31mW/cm² (34 V/m).Rectenna arrays, with series and parallel interconnections, have been developed and measured. Output DC voltages and powers have been doubled and quadrupled using two andfour rectenna elements, respectively.

Ce travail de thèse s’inscrit dans les efforts actuellement réalisés, pour améliorer l’efficacité des pinces optiques conventionnelles qui permettent de manipuler sans contact des objets de quelques dizaines de nanomètres à quelques dizaines de micromètres avec une extrême précision et trouvent de nombreuses applications en biophysique et sciences de colloïdes.L’objectif de cette thèse a été d’explorer une nouvelle approche pour la réalisation de Nanopinces Optiques. Elle s’appuie sur l’utilisation de cavités à cristaux photoniques à modes de Bloch lents. Ces cavités peuvent être efficacement et facilement excitées par un faisceau Gaussien à incidence normale. Contrairement aux pinces optiques conventionnelles, des objectifs à faibles ouvertures numériques peuvent être utilisés. Les performances attendues en termes de piégeage vont bien au-delà de limitations imposées par la limite de diffraction pour les pinces conventionnelles. Ce travail démontre expérimentalement l’efficacité de l’approche. Cette thèse comporte deux parties principales. Dans un premier temps, il a fallu monter un banc expérimental pour mener nos études. Nous avons construit un banc optique, interfacé les instruments, et développé des applications logicielles pour analyser les données. Deux éléments importants ont présidé à sa construction : - Le développement d’un système optique permettant d’exciter les nanostructures photoniques - la conception d’un système d’imagerie pour suivre les nanoparticules. La seconde partie de ce travail a porté sur la mise en évidence du piégeage optique à l’aide de nanostructure à base de cristaux photonique. Nous avons d’abord montré que même des cavités possédant des coefficients de qualités modérés (quelques centaines) permettait d’obtenir des pièges optiques dont l’efficacité est d’un ordre de grandeur supérieur à celui de pinces conventionnels. Fort de ce résultat, nous avons exploré un nouveau type de cavité à cristaux photoniques s’appuyant sur une approche originale : des structures bi-périodiques. Nous avons montré qu’à l’aide de cette approche des facteurs de qualités de l’ordre de plusieurs milliers étaient facilement atteignable. A l’aide de ces nouvelles structures, nous sommes arrivés aux résultats le plus important de ce travail : le piégeage de nanoparticules de 250nm de rayon avec une puissance optique incidente de l’ordre du milliwatt. Une analyse fine du mouvement de la nanoparticule, nous a permis de trouver la signature du mode de Bloch lent. / This thesis aims at improving the efficiency of conventional optical tweezers (cOT). They allow to manipulate objects with dimension from a few tens of nanometer to a few tens of micrometers with a high accuracy and without contact. This has numerous applications in biophysics and colloidal science. This thesis investigates a new approach for optical nanotweezers. It uses a photonic crystal (PC) cavity which generates a slow Bloch mode. This cavity can be effectively and easily excited with a Gaussian beam at the normal incidence. Contrarily to cOT, objective with a small numerical aperture can be used. The expected performances in terms of trapping go well beyond the diffraction limit of cOT. This work demonstrates experimentally the efficacy of approach. This thesis is divided in two main sections. First, we had to set up an experimental bench to carry out to our study. We built the optical bench interface instruments and develop programs to analyze the data. Two essential elements have been considered: - The development of the optical system allowing the excitation of the photonics nanostructure. - The design an imaging system to track nanoparticles. Second, we have focus on the demonstration of the optical trapping. We started by with a low Q factor (few hundred) cavity. Trapping efficiency of an order of magnitude higher than cOT has been demonstrated. Then, we have explored a new king of PC cavity based on double period structure. We show that thanks to this approach high Q factor of several thousand are easily reached. With this structure, we managed to trap 250nm polystyrene beads, with an optical power of the order of a milliwatt. A deep analysis of the nanoparticle trajectories allowed us to find a slow Bloch mode signature.

Η υπερθερμία αποτελεί μια επικουρική μέθοδο θεραπείας του καρκίνου και η βιοϊατρική έρευνα τις τελευταίες δεκαετίες, με σκοπό την εκμετάλλευση και την ανάδειξη των ιδιοτήτων της μεθόδου, στοχεύει στην εφαρμογή της στην κλινική πράξη. Μια προσπάθεια με παρόμοιο σκοπό γίνεται τα τελευταία χρόνια στο Εργαστήριο Μικροκυμάτων και Οπτικών Ινών (ΕΜΟΙ) της σχολής Ηλεκτρολόγων Μηχανικών και Μηχανικών Υπολογιστών (ΗΜΜΥ) του Εθνικού Μετσόβιου Πολυτεχνείου, όπου έχει σχεδιαστεί και κατασκευαστεί ένα μικροκυματικό σύστημα υπερθερμίας. Το προτεινόμενο σύστημα ενσωματώθηκε σε ένα τρισδιάστατο σύστημα παθητικής μικροκυματικής ραδιομετρικής απεικόνισης (ΜiRaIS), το οποίο παρέχει τη δυνατότητα παρακολούθησης των μεταβολών της θερμοκρασίας και της αγωγιμότητας της υπό εξέταση περιοχής σε πραγματικό χρόνο και μελετήθηκε και κατασκευάστηκε στα πλαίσια παλαιότερης διδακτορικής διατριβής στο ίδιο εργαστήριο της σχολής ΗΜΜΥ. Στην παρούσα διδακτορική διατριβή γίνεται η θεωρητική και πειραματική μελέτη του προτεινόμενου συστήματος υπερθερμίας. Η αρχή λειτουργίας του συστήματος είναι όμοια με εκείνη του MiRaIS και βασίζεται στη χρήση μιας ελλειψοειδούς αγώγιμης κοιλότητας για εστίαση της ακτινοβολίας επιλεκτικά στους ιστούς που χρήζουν θεραπείας. Ο ανακλαστήρας για εστίαση που κατασκευάστηκε και χρησιμοποιήθηκε στην πειραματική διαδικασία, βελτιώνει την εργονομία του συστήματος, διατηρώντας παράλληλα της ιδιότητες εστίασης του πρωτότυπου ελλειψοειδούς. Στα πλαίσια της παρούσας διατριβής πραγματοποιήθηκε αρχικά η θεωρητική μελέτη και μοντελοποίηση της διάταξης με σκοπό την εξακρίβωση των ιδιοτήτων εστίασης του συστήματος και στη συνέχεια επιχειρήθηκε η βελτίωση των ιδιοτήτων αυτών με χρήση διατάξεων διηελκτρικών υλικών, καθώς και πειραματικές μετρήσεις του συνολικού συστήματος υπερθερμίας-μικροκυματικής ραδιομετρίας. Η θεωρητική ηλεκτρομαγνητική μελέτη του συστήματος έγινε με τη χρήση ενός εμπορικά διαθέσιμου υπολογιστικού πακέτου προσομοίωσης (XFdtd, Remcom Inc.), το οποίο χρησιμοποιεί τη μέθοδο των πεπερασμένων διαφορών στο πεδίο του χρόνου για την επίλυση ηλεκτρομαγνητικών προβλημάτων. Ερευνώνται τρεις διατάξεις διηλεκτρικών υλικών με σκοπό τη βελτίωση των ιδιοτήτων εστίασης του συστήματος, οι οποίες επικεντρώνονται στη μελέτη του βάθους διείσδυσης της ακτινοβολίας και της χωρικής διακριτικής ικανότητας. Τα υλικά τοποθετούνται είτε στο εσωτερικό του ελλειψοειδούς είτε γύρω από το μοντέλο κεφαλιού ως στρώματα προσαρμογής, με σκοπό την επίτευξη βηματικής αλλαγής της διηλεκτρικής σταθεράς στη διεπιφάνεια αέρα-μοντέλο ανθρώπινου κεφαλιού. Τα αποτελέσματα καταδεικνύουν τα πλεονεκτήματα από τη χρήση των διηλεκτρικών υλικών, καθώς παρουσιάζεται βελτίωση και στις δυο παραμέτρους των ιδιοτήτων εστίασης, ανάλογα με τη διάταξη που χρησιμοποιείται, τη θέση του μοντέλου κεφαλιού στο εσωτερικό του συστήματος και τη συχνότητα λειτουργίας. Για τη διενέργεια των πειραμάτων, η πειραματική διάταξη τοποθετήθηκε σε ανηχοϊκό θάλαμο, ο οποίος εξασφαλίζει την απομόνωσή της από τον περιβάλλοντα χώρο. Στις πειραματικές διαδικασίες που ακολουθήθηκαν, χρησιμοποιήθηκαν ομοιώματα, τα οποία στη φάση της υπερθερμίας υπέδειξαν τις περιοχές εστίασης της ενέργειας για την εκάστοτε συχνότητα ακτινοβολίας, ενώ στη φάση της μικροκυματικής ραδιομετρίας βοήθησαν στη μελέτη της θερμοκρασιακής διακριτικής ικανότητας του συστήματος. Η μέθοδος της μικροκυματικής ραδιομετρίας χρησιμοποιήθηκε για την παρακολούθηση των μεταβολών της θερμοκρασίας της ακτινοβολούμενης περιοχής κατά τη διάρκεια των συνεδριών της υπερθερμίας. Επίσης, κατά τη διάρκεια των πειραμάτων πραγματοποιήθηκαν μετρήσεις με στρώματα προσαρμογής από διηλεκτρικά υλικά, τα οποία τοποθετήθηκαν γύρω από το αντικείμενο ενδιαφέροντος και βοήθησαν στην πληρέστερη κατανόηση της επίδρασης της παρουσίας τους στις ιδιότητες εστίασης του συστήματος και στην επιβεβαίωση των αντίστοιχων θεωρητικών αποτελεσμάτων. / The application of hyperthermia process has been widely used in clinical research and efforts are being made for its implementation in clinical practice, as many researchers have used this method as an adjunct treatment procedure for cancer. During the past two decades, a great deal of research has been carried out, with the aim of developing effective techniques for hyperthermia treatment, primarily using RF, microwave and ultrasound energy. A similar effort is carried out in the Laboratory of Microwaves and Fiber Optics (MFOL), School of Electrical and Computer Engineering, National Technical University of Athens (NTUA), where a proposed hyperthermia system has been designed and constructed. A system for deep brain hyperthermia treatment, designed to also provide passive measurements of temperature and/or conductivity variations inside the human body, is presented in the present PhD thesis. The proposed system comprises both therapeutic and diagnostic modules, operating in a totally contactless way, based on the use of an ellipsoidal beamformer to achieve focusing on the areas under treatment and monitoring. The radiometry monitoring module, the Three Dimensional Passive Microwave Radiometry Imaging System (MiRaIS), has been studied, designed and constructed in the framework of a previous PhD thesis in the same laboratory of MFOL. In the present thesis, the proposed system is theoretically and experimentally studied. The operation principal is based on the use of an ellipsoidal conductive wall cavity for focusing the emitted radiation on the tissues that should accept treatment. The ellipsoidal cavity, which was constructed and used in the experimentation procedure, is newly developed and improves the system’s ergonomics retaining at the same time the focusing properties of the prototype system. In the framework of the present work, theoretical modeling and experimentation of the proposed system is carried out in order to examine and improve its focusing attributes. In the theoretical study, three setups are investigated for the improvement of the system’s focusing properties (e.g. penetration depth of the electromagnetic field, spatial sensitivity) using dielectric materials. The research is carried out with the use of a commercially available software tool, XFdtd (Remcom Inc.). The materials are placed inside the ellipsoidal or used as matching layers around the head model for the achievement of a stepped change of the refraction index on the air-human head model interface. The results revealed the possible advantages of using matching dielectric materials, as improvement on the focusing properties of the system is clearly observed, depending on the setup used, the position of the head model inside the system and the operating frequency. The experiments were performed inside an anechoic chamber providing maximum accuracy by avoiding all possible EMC/EMI issues. Along with the hyperthermia experiments, the implementation of the microwave radiometry process was also tested with the proposed system. Microwave radiometry could provide the temperature monitoring of the radiated area during the hyperthermia sessions. In the experimental procedures water phantoms were used, which during hyperthermia indicated the energy absorbing areas at the irradiation frequency, while during microwave radiometry revealed the system’s temperature sensitivity. Also, measurements were conducted using dielectric matching layers, placed around the medium of interest, in order to fully understand the effect of those materials on the system’s focusing properties as well as to confirm the respective theoretical results. Taking into consideration the present study and the advantage of the non invasive character of the proposed brain hyperthermia system, it is concluded that further research is required in order to explore its potentials at becoming a part of the standard treatment protocol of brain malignancy in the future.