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Electrical insulation papers are a widely used group of papers in insulation applications and has been used for more than 100 years. Common applications include use as the dielectric medium in capacitors and insulation material in cables, bushings and transformers. As new advances in the study of the electrical properties of paper are made, the prospects of future applications grow. One interesting prospect is the use of paper as a substrate in sensing devices, biodegradable, printed and flexible electronics. Paper is a renewable and recyclable material and it would therefor be desirable to replace non-renewables materials such as plastics with paper as e.g., substrate in printed electronics. For this to be feasible the paper must be able to meet the electric and dielectric requirements of the intended application, among which low dielectric losses is a key parameter. One way to alter and control the electric and dielectric properties of a paper sample is through the selection of different ions in the ion-exchange step of the paper making process. In a collaboration between KTH Royal Institute of Technology and RISE - Research Institutes of Sweden AB working within a greater Digital Cellulose Center (DCC) project, this thesis aims to measure and characterise the dielectric response of a set of novel ion-exchanged paper samples together with a set of reference papers currently used in electrical applications. The greater goal of RISE work is to understand and map the influence of ion choice in order to better understand and control the dielectric properties of paper. The samples were measured using an impedance spectroscopy method from which capacitance and permittivity can be calculated. A parallel plate Kelvin guard-ring capacitor consisting of two electrodes and a guard ring placed in a custom made climate controlled chamber was used to measure the samples in different environmental conditions. The results show that the choice of ion used in the ion-exchanged papers heavily influence the samples dielectric response, both its dielectric constant and dielectric losses. Further, the choice of ion valence appears correlated with the change in responses; monovalent ions had much greater influence than bivalent ions. This effect appears to stem from monovalent ions having a greater mobility within the bulk material, more research is however needed for a definite answer. / Elektriska isoleringspapper är en flitigt använd grupp av papper i isoleringsapplikationer och har använts i mer än 100 år. Vanliga applikationsområden inkluderar användning som dielektriskt medium i kondensatorer och isoleringsmaterial i kablar, genomföringar och transformatorer. I takt med att nya framsteg görs inom olika pappers elektriska egenskaper växer utsikterna för framtida tillämpningar. En intressant möjlighet är användningen av papper som substrat för sensorer, biologiskt nedbrytbar, tryckt och flexibel elektronik. Papper är ett förnybart och återvinningsbart material och det vore därför önskvärt att ersätta icke förnybara material som plast med papper som t.ex. substrat i tryckt elektronik. För att detta ska vara genomförbart måste papperet kunna uppfylla de elektriska och dielektriska kraven för den avsedda applikationen, bland vilka låga dielektriska förluster är en nyckelparameter. Ett sätt att ändra och kontrollera de elektriska och dielektriska egenskaperna hos ett pappersprov är genom valet av olika joner i jonbytessteget i papperstillverkningsprocessen. I ett samarbete mellan KTH Kungliga Tekniska Högskolan och RISE Research Institutes of Sweden AB som arbetar inom ett större Digital Cellulose Center-projekt, syftar denna avhandling till att mäta och karakterisera den dielektriska responsen hos en uppsättning nya jonbytta pappersprover tillsammans med en uppsättning referenspapper. Det övergripande målet i RISE arbete är att förstå och kartlägga påverkan av jonval för att bättre förstå och kontrollera pappers dielektriska egenskaper. Proverna mättes med en impedansbaserad mätmetod från vilken kapacitans och permittivitet kan beräknas. En Kelvin plattkondensator bestående av två elektroder och en skyddsring placerad i en skräddarsydd klimatkontrollerad kammare användes för att mäta proverna under olika miljöförhållanden. Resultaten visar att valet av jon som används i jonutbytet kraftigt påverkar provets dielektriska respons, både dess dielektriska konstant och dielektriska förluster. Vidare verkar valet av jonvalens vara korrelerat med förändringen i frekvenssvar; envärda joner hade mycket större inflytande än tvåvärda joner. Denna effekt verkar bero på att envärda joner har en större rörlighet inom bulkmaterialet, mer forskning krävs dock för ett definitivt svar.

<p>An electro-optical sensor module was designed to monitor the level of dissolved oxygen (DO) using the method of frequency domain fluoroscopy. Frequency domain fluoroscopy is an optical method that detects the concentration of an analyte by indirectly monitoring the fluorescent lifetime decay. A planar film containing oxygen sensitive fluorophores interacts with a liquid solution, where the percent DO dictates the fluorescent lifetime decay. Amplitude modulated LED emission is created using an electrically implemented oscillator, exciting the oxygen sensitive fluorophores. The emission light from the fluorophores is detected by a photodiode and conditioned. The timing characteristics of the excitation and emission light waveforms are interpreted by a microcontroller. Time delay values have been correlated to actual percent DO values experimentally, and appropriate data modeling has been implemented for calibration purposes. This design is appropriate for application in bioreactors, presenting a functional and cost effective design. Future research can be performed to extrapolate the microcontroller platform to host a pH module, cell number module and glucose module, providing sufficient feedback to an automated bioreactor systems.</p> / Master of Applied Science (MASc)

Fixed Broadband Wireless Access (FBWA) is a technology aimed at providing high-speed wireless Internet access, over a wide area, from devices such as personal computers and laptops. FBWA channels are defined in the range of 1-20 MHz which makes the RF front end (RFE) design extremely challenging. In its pursuit to standardize the Broadband Wireless Access (BWA) technologies, IEEE working group 802.16 for Broadband Wireless Access has released the fixed BWA standard IEEE 802.16 – 2004 in 2004. This standard is further backed by a consortium, of leading wireless vendors, chip manufacturers and service providers, officially known as Wireless Interoperability for Microwave Access (WiMAX). In general, any wireless base station (BS), supporting a number of contiguous Frequency Division Multiplexed (FDM) channels has to incorporate an RF front end (RFE) for each RF channel. The precise job of the RFE is to filter the desired channel from a group of RF channels, digitize it and present it to the subsequent baseband system at the proper sampling rate. The system essentially has a bandpass filter (BPF) tuned to the channel of interest followed by a multiplier which brings the channel to a suitable intermediate frequency (IF). The IF output is digitized by an ADC and then brought to the baseband by an appropriate digital multiplier. The baseband samples, thus generated, are at the ADC sampling rate which is significantly higher than the target sampling rate, which is defined by the wireless protocol in use. As a result a sampling rate conversion (SRC) is performed on these baseband samples to bring the channel back to the target sampling rate. Since the input sampling rate need not be an integer multiple of the target sampling rate, Fractional SRC (FSRC) is required in most of the cases. Instead of using a separate ADC and IF section for each individual channels, most systems use a common IF section, followed by a wideband ADC, which operates over a wide frequency band containing a group of contiguous FDM channels. In this case a channelizer is employed to digitally extract the individual channels from the digital IF samples. We formally call this system a receiver channelizer. Such an implementation presents considerable challenge in terms of the computational requirement and of course the cost of the BS. The computational complexity further goes up for FBWA system where channel bandwidth is in the order of several MHz. Though such a system has been analyzed for narrow band wireless systems like GSM, to the best of our knowledge no analysis seems to have been carried out for a wideband system such as WiMAX. In this work, we focus on design of a receiver channelizer for WiMAX BS, which can simultaneously extract a group of contiguous FDM RF channels supported by the BS. The main goal is to obtain a simple, low cost channelizer architecture, which can be implemented in an FPGA. There are a number of techniques available in the literature, from Direct Digital Conversion to Polyphase FFT Filter Banks (PFFB), which can do the job of channelization. But each of them operates with certain constraints and, as a result, suits best to a particular application. Further all of these techniques are generic in nature, in the sense that their structure is independent of any particular standard. With regard to computational requirement of these techniques, PFFB is the best, with respect to the number of complex multiplications required for its implementation. But it needs two very stringent conditions to be satisfied, viz. the number of channels to be extracted is equal to the decimation factor and the sampling rate is a power of 2 times baseband bandwidth. Clearly these conditions may not be satisfied by different wireless communication standards, and in fact, this is not satisfied by the WiMAX standard. This gives us the motivation to analyze the receiver channelizer for WiMAX BS and to find an efficient and low cost architecture of the same. We demonstrate that even though the conditions required by PFFB are not satisfied by the WiMAX standard, we can modify the overall architecture to include the PFFB structure. This is achieved by dividing the receiver channelizer into two blocks. The first block uses the PFFB structure to separate the desired number of channels from the input samples. This process also achieves an integer SRC by a factor that is equal to the number of channels being extracted. This block generates baseband outputs whose sampling rates are related to their target sampling rate by a fractional multiplication factor. In order to bring the channels to their target sampling rate, each output from the PFFB block is fed to a FSRC block, whose job is to use an efficient FSRC algorithm to generate the samples at the target sampling rate. We show that the computational complexity, as compared to the direct implementation, is reduced by a factor, which is approximately equal to the square of the number of channels. After mathematically formulating the receiver channelizer for WiMAX BS, we perform the simulation of the system using a software tool. There are two basic motives behind the simulation of the system which has a mathematical model. Firstly, the software simulation will give an idea whether the designed system is physically realizable. Secondly, this will help in designing the logic for different blocks of the system. Once these individual blocks are simulated and tested, they can be smoothly ported onto an FPGA. For simulation purpose, we parameterize the receiver channelizer in such a way that it can be reconfigured for different ADC sampling rates and IF frequencies, by changing the input clock rate. The system is also reconfigurable in terms of the supported channel bandwidth. This is achieved by storing all the filter coefficients pertaining to each channel type, and loading the required coefficients into the computational engine. Using this methodology we simulate the system for three different IF frequencies (and the corresponding ADC sampling rates) and three different channel types, thus leading to nine different system configurations. The simulation results are in agreement with the mathematical model of the system. Further, we also discuss some important implementation issues for the reconfigurable receiver channelizer. We estimate the memory requirement for implementing the system in an FPGA. The implementation delay is estimated in terms of number of samples. The thesis is organized in five chapters. Chapter 1 gives a brief introduction about the WiMAX system and different existing channelization architecture followed by the outline of the proposed receiver channelizer. In chapter 2, we analyze the proposed receiver channelizer for WiMAX BS and evaluate its computational requirements. Chapter 3 outlines the procedure to generate the WiMAX test signal and specification of the all the filters used in the system. It also lists the simulation parameters and records the results of the simulation. Chapter 4 presents the details of a possible FPGA implementation. We present the concluding remarks and future research directions in the final chapter.

High-frequency wave phenomena is observed in many physical settings, most notably in acoustics, electromagnetics, and elasticity. In all of these fields, numerical simulation and modeling of the forward propagation problem is important to the design and analysis of many systems; a few examples which rely on these computations are the development of metamaterial technologies and geophysical prospecting for natural resources. There are two modes of modeling the forward problem: the frequency domain and the time domain. As the title states, this work is concerned with the former regime. The difficulties of solving the high-frequency wave propagation problem accurately lies in the large number of degrees of freedom required. Conventional wisdom in the computational electromagnetics commmunity suggests that about 10 degrees of freedom per wavelength be used in each coordinate direction to resolve each oscillation. If K is the width of the domain in wavelengths, the number of unknowns N grows at least by O(K^2) for surface discretizations and O(K^3) for volume discretizations in 3D. The memory requirements and asymptotic complexity estimates of direct algorithms such as the multifrontal method are too costly for such problems. Thus, iterative solvers must be used. In this dissertation, I will present fast algorithms which, in conjunction with GMRES, allow the solution of the forward problem in O(N) or O(N log N) time. / text

Τα συστήματα πολλαπλών κεραιών στον πομπό και στο δέκτη (MIMO) αποτελούν βασικά μέτωπα ανάπτυξης των ασύρματων επικοινωνιών. Ωστόσο, η εφαρμογή της τεχνολογίας MIMO στα κινητά δίκτυα επικοινωνιών αντιμετωπίζει το πρακτικό πρόβλημα της ενσωμάτωσης πολλαπλών κεραιών σε μικρά κινητά τερματικά. Με σκοπό την αντιμετώπιση του εμποδίου αυτού, δημιουργήθηκε ένα άλλο σημαντικό μέτωπο έρευνας, αυτό των συνεργατικών επικοινωνιών. Στο πλαίσιο της παρούσας διδακτορικής διατριβής ασχοληθήκαμε με την ανάπτυξη και μελέτη αλγορίθμων επεξεργασίας σήματος για τα δύο παραπάνω συστήματα. Σχετικά με τα συστήματα MIMO η πρωτοποριακή έρευνα που πραγματοποιήθηκε στα Bell labs στα μέσα της δεκαετίας του ΄90, απέδειξε ότι η χρήση πολλαπλών κεραιών μπορεί να οδηγήσει σε σημαντική αύξηση της χωρητικότητας των ασύρματων συστημάτων βελτιώνοντας την αξιοπιστία της μετάδοσης. Προκειμένου να αξιοποιηθούν οι παραπάνω δυνατότητες απαιτείται η σχεδίαση σύνθετων δεκτών MIMO. Προς αυτήν την κατεύθυνση έχει στραφεί ένας μεγάλος αριθμός μεθόδων ισοστάθμισης του καναλιού και πιο συγκεκριμένα δεκτών ανατροφοδότησης αποφάσεων. Δεδομένου ότι σε ευρυζωνικά συστήματα επικοινωνιών το ασύρματο κανάλι είναι άγνωστο στο δέκτη και μεταβάλλεται χρονικά, στραφήκαμε προς τις προσαρμοστικές μεθόδους ισοστάθμισης. Στα πλαίσια της διαριβής αναζήτησαμε προσαρμοστικούς αλγόριθμους κατάλληλους για τη σχεδίαση προσαρμοστικών ισοσταθμιστών MIMO DFE με τα εξής χαρακτηριστικά: 1) να παρουσιάζουν απόδοση (ταχύτητα σύγκλισης) συγκρίσιμη με αυτή του RLS, 2) η υπολογιστική τους πολυπλοκότητα να είναι μικρότερη από αυτή του RLS και 3) να είναι αριθμητικά ευσταθείς. ΄Εχει αποδειχθεί ότι προσαρμοστικοί αλγόριθμοι που βασίζονται στη μέθοδο των συζυγών κλίσεων (conjugate gradient (CG)) πληρούν τις παραπάνω προϋποθέσεις. Αρχικά αναζητήσαμε τεχνικές που βασίζονται στη μέθοδο αυτή και χρησιμοποιούνται σε προβλήματα προσαρμοστικού φιλτραρίσματος και πιο ειδικά, στο πρόβλημα προσαρμοστικής ισοστάθμισης διαύλου στη περίπτωση SISO. Πιο συγκεκριμένα, υλοποιήσαμε έναν προσαρμοστικό αλγόριθμο στο πεδίο των συχνοτήτων που επεξεργάζεται τα δεδομένα κάθε φορά που λαμβάνεται ένα νέο εισερχόμενο πακέτο δεδομένων. Ο προτεινόμενος ισοσταθμιστής πετυχαίνει μια πολύ καλή απόδοση, ενώ οι υπολογιστικές του απαιτήσεις είναι πολύ χαμηλές. Στη συνέχεια αναπτύξαμε τρεις νέους αλγορίθμους προσαρμοστικής ισοστάθμισης συχνοτικά επιλεκτικών συστημάτων MIMO, που βασίζονται στη μέθοδο CG και στις προβολές Galerkin. Το πρόβλημα σχεδιασμού προσαρμοστικών MIMO DFE αντιμετωπίζεται ως ένα πρόβλημα επίλυσης γραμμικών εξισώσεων, με πολλαπλά δεξιά μέλη, που εξελίσσεται στο χρόνο. Επισημαίνουμε ότι τα σχήματα που προτείνουμε θα μπορούσαν να αποτελέσουν ένα γενικότερο πλαίσιο σχεδίασης προσαρμοστικών δεκτών για συχνοτικά επιλεκτικά συστήματα MIMO, με ιδιότητες σύγκλισης παρόμοιες με αυτές του RLS, έχοντας, ωστόσο, μικρότερες υπολογιστικές απαιτήσεις. Στα πλαίσια της παρούσας διδακτορικής διατριβής αναπτύξαμε τεχνικές εκτίμησης καναλιού για συνεργατικά δίκτυα με N αναμεταδότες που είτε ενισχύουν και αναμεταδίδουν ή αποκωδικοποιούν και αναμεταδίδουν το λαμβανόμενο σήμα. ΄Ολες οι τεχνικές εκτίμησης που προτείναμε υλοποιούνται εξ΄ ολοκλήρου στο πεδίο των συχνοτήτων. Αρχικά παρουσιάσαμε τεχνικές που βασίζονται στη μετάδοση πιλοτικών συμβόλων σε συγκεκριμένες συχνοτικές συνιστώσες. Στη συνέχεια αποδείξαμε ότι όλα τα κανάλια από την πηγή μέσω των αναμεταδοτών προς τον προορισμό μπορούν να εκτιμηθούν τυφλά εάν γνωρίζουμε τις φάσεις της απόκρισης συχνότητας του ασύρματου καναλιού μεταξύ πηγής και προορισμού.. Επιπρόσθετα, πραγματοποιήθηκε ϑεωρητική ανάλυση της απόδοσης των προτεινόμενων σχημάτων η οποία επαληθεύτηκε μέσω προσομοιώσεων σε υπολογιστή. Τέλος, αξιολογήσαμε πειραματικά διάφορα πρωτόκολλα συνεργατικής επικοινωνίας (AF, DF, SF) και τεχνικές κατανεμημένης χωροχρονικής επεξεργασίας DSTC για συνεργατικά δίκτυα σε μια πλατφόρμα υλοποίησης πραγματικού χρόνου που χρησιμοποιεί επεξεργαστές ψηφιακής επεξεργασίας σήματος. Διαπιστώσαμε ότι τα πειραματικά αποτελέσματα συμφωνούν πλήρως με τα θεωρητικά. / Systems employing multiple antennas at the transmitter and the receiver, known as MIMO (multiinput multioutput) systems, as well as space time coding techniques developed for such systems, are two of the main technologies employed for the evolution of wireless communications. However, the application of MIMO technology to mobile networks, often faces the practical implementation problem of having too many antennas on a small mobile terminal. In an attempt to overcome such a severe limitation, cooperative communication schemes have been proposed. This PhD dissertation, described our work on the design and analysis of signal processing algorithms for the two aforementioned systems, as is described in detail next. Concerning MIMO systems, the pioneering work performed at Bell Labs in the middle of the nineties, proved that the use of multiple antennas can lead to a significant increase in wireless systems capacity. To exploit this potential, sophisticated MIMO receivers should be designed. To this end, a large amount of channel equalizers and, more specifically, decision feedback equalizers has been proposed. Because these assumptions are difficult to meet in high rate single carrier systems, we have focused our attention on decision feedback equalizers. . Our main goal is to derive algorithms for updating the MIMO DFE filters with the following characteristics: 1) convergence properties similar to these of the RLS 2) more computationally efficient than RLS and 3) numerically stable. It is known that adaptive algorithms based on the CG (conjugate gradient) have the above characteristics We initially studied this method as an iterative method for solving linear equations and we pointed out the main differences with the steepest descent method, on which the LMS algorithm is based. An extended search of adaptive DFE algorithms, based on the CG method was carried out. More specifically, a new block adaptive CG algorithm was developed. In the resulting algorithm, one CG iteration per block update is executed. In order to reduce even more the complexity, the algorithm was implemented in the Frequency Domain. The proposed equalizer offers a good performance - complexity trade off. Three new adaptive equalization algorithms for wireless systems operating over frequency selective MIMO channels, based on the CG method and the Galerkin projection method, are proposed. The problem of MIMO decision feedback equalizer (DFE) design is formulated as a set of linear equations with multiple righthand sides (RHSs) evolving in time. These schemes provide a flexible framework in MIMO adaptive equalization design to implement schemes with convergence properties comparable to the RLS, but of lower computational cost. Furthermore, we worked on channel estimation for cooperative communication networks, where the nodes either simply amplify and forward the received signal, or they decode and transmit the signal (DF). We first propose efficient channel estimation techniques for relay networks with N relays. The new methods are implemented in the frequency domain (FD). Initially, training based techniques are presented, where the training pilots are multiplexed with the data in the frequency domain. It is then shown that all the channels in the network can be estimated blindly provided that we know the phases of the frequency response of the (Source → Destination) channel. Thus, by making use of a small number of pilots in only one link (the sourcetodestination link) we can estimate all the other channels (Source→Relay i→Destination) in the network. A theoretical performance study of the proposed algorithms is presented and closed form expressions for the mean squared channel estimation error are provided. The presented theoretical analysis is verified by extensive Monte Carlo simulations. The application of the derived schemes to the DF case, and the impact of erroneous detection to their performance are also studied. Finally, we investigated experimentally four cooperative relaying schemes: amplify and forward (AF), detect and forward (DF), cooperative maximum ratio combining (CMRC) and distributed spacetime coding (DSTC), and one novel selection relaying (SR) scheme on a realtime DSP based testbed. The experimental results are fairly close to the ones predicted by theory

Ces travaux de recherche portent sur la problématique CEM (Compatibilité Electromagnétique) en électronique de puissance. Cette étude s'intéresse particulièrement à la modélisation HF (haute fréquence) des convertisseurs d'énergie dans le but d'étudier la propagation des perturbations conduites vers le réseau avec ou sans l’utilisation du RSIL (Réseau Stabilisateur d'Impédance de Ligne). Une première partie présente les outils de modélisation des sources de perturbation dans les convertisseurs statiques.La seconde partie est consacrée à la modélisation HF d'un système d'entraînement à vitesse variable. L'onduleur de tension triphasé est représenté par trois générateurs équivalents afin de reconstituer le découpage des tensions de sortie. Un modèle HF du câble blindé de 4 conducteurs tenant compte de la dissymétrie est ensuite proposé. Les résultats de simulation ont été validés par des relevés expérimentaux. La comparaison montre qu'il est possible de modéliser correctement le comportement HF du dispositif jusqu'à 20MHz.Une troisième partie porte sur la propagation des perturbations conduites vers le réseau sans RSIL. Il a fallu pour cela déterminer et modéliser l'impédance du réseau. L'influence du pont redresseur à diodes sur la propagation des perturbations de mode commun a ensuite été étudiée. Les résultats de simulation montrent que l'impact de ces perturbations sur la tension réseau est prépondérant lorsque le pont redresseur est à l'état bloqué. Les résultats expérimentaux ont permis de valider cette étude. Ce travail se termine par une étude préliminaire sur l'association de deux convertisseurs connectés localement à une même source d'énergie / These research works focus on EMC (Electromagnetic Compatibility) in power electronics systems. Specifically, the study focuses on HF (high frequency) modeling of the power converters in order to study the conducted emissions toward the power grids with or without the use of an LISN (Line Impedance Stabilisation Network). The first part presents the modeling tools of the electromagnetic emissions sources in power converters.The second part describes the HF modeling method of an adjustable speed drive (ASD) that will be used to estimate the conducted emissions. In a first part, a behavioural model of PWM inverter is proposed as an EMI noise source. Then, a model of the shielded 4-wire energy cable that taking into account of the dissymmetry structure is proposed and validated in the frequency domain for two different lengths. The comparison of measurement and simulation results of conducted emissions (with LISN) shows the good compromise between the simulation duration and accuracy of the results.A third part is dedicated to the propagation of conducted emissions toward the power grid without using a LISN. The first stage consists in proposing a model impedance of the network impedance. The influence of the bridge rectifier diodes on the propagation paths of common mode disturbances has been studied in the second step. The simulation results show that the impact of these disturbances on the network voltage is more important when the bridge rectifier is normally off-state. The experimental results have validated this study. This work concludes with a preliminary study on the association of two converters connected locally to a single energy source

Cette thèse constitue un ensemble de travaux et de réflexions sur la question de la modélisation d’expériences en nano-optique utilisant la méthode des différences finies dans le domaine fréquentiel (FDFD) et la méthode des différences finies dans le domaine temporel (FDTD). D’abord, un code FDFD bidimensionnel, dédié au calcul de modes propres de guides d’ondes optiques, a été mis en œuvre et testé à travers une comparaison avec des résultats publiés. Dans une deuxième grande partie, nous étudions le piégeage optique de petites particules (de taille microscopique) à l’aide d’une antenne à nano-ouverture papillon (BNA) gravée à l’extrémité d’une sonde de microscope optique métallisée. Le confinement de lumière obtenue à la résonance de la nano-antenne permet un piégeage 3-D des nanoparticules de latex. Une étude systématique a été menée pour quantifier la puissance de la lumière incidente nécessaire pour un piégeage stable. Un bon accord entre les résultats expérimentaux et numériques a été obtenu dans le cas d’une BNA opérant dans l’eau à _ = 1064 nm pour le piégeage de particules de latex de 250 nm de rayon. En outre, les résultats numériques pour de plus petites particules sont présentés et montrent qu’une telle configuration est capable de piéger des particules avec des rayons aussi petits que 30 nm. Troisièmement, nous avons étudié le processus de piégeage optique basé sur l’amélioration du confinement, non seulement du champ électrique comme dans le cas de la BNA, mais aussi du magnétique que peut exhiber l’antenne métallique type diabolo (DA). Cette dernière a été récemment proposée car elle présente une résonance avec un fort confinement magnétique. Nous avons amélioré le design afin qu’une double résonance, électrique et magnétique, ait lieu au centre de la nano-antenne. Ce double confinement a ensuite été exploité pour exalter le gradient de champ au voisinage de l’antenne et ainsi aboutir à de meilleures efficacités de piégeage (moindre puissance). De plus, les résultats des simulations montrent que le processus de piégeage dépend fortement des dimensions des particules et que, pour des géométries particulières, un piégeage sans contact peut être réalisé. Cette structure doublement résonnante ouvre la voie à la conception d’une nouvelle génération de nano-pinces optiques à forte efficacit / This thesis is a set of work and reflections on modeling the experiments in nano-optics by using the finite difference method in the frequency domain (FDFD), and in time domain (FDTD). First, a two-dimensional code FDFD, dedicated to the calculation the eigenmodes of optical waveguides, has been implemented and tested through a comparison with results found in the literature. In a second large part, we study the optical trapping of small particles (of microscopic size) by using a bowtie nanoaperture antenna (BNA) engraved at the end of a metal-coated near-field optical microscope tip. The confinement of light obtained at the resonance of the nano-antenna allows 3-D trapping of latex nanoparticles. A systematic study was conducted to quantify the power of incident light necessary for stable trapping. Good agreement between the experimental and numerical results was obtained in the case of a BNA operating in water at _ = 1064 nm for the trapping of latex particles having a radius of 250 nm-radius. In addition, numerical results for smaller particles are presented and show that such configuration is capable of trapping particles with radii reaching 30 nm. Third, we studied the optical trapping process based on improved confinement of the electric field as in the case of the BNA, but also of the magnetic field, by using a metallic diabolo shape antenna (DA). This latter has been recently proposed because it exhibits resonance with a strong magnetic field confinement. We have improved the design in such a way that a double resonance, electric and magnetic, takes place in the center of the nano-antenna. This dual confinement was then used in order to enhance the field gradient in its vicinity and thus obtain better efficiencies of the trapping (less power). In addition, the simulation results show that the trapping process is greatly dependent of the particles size, and also show that, for specificl geometries, a trapping without contact can be achieved. This doubly resonant structure opens the way to the conception of a new generation of optical nano-tweezers with high efficiency.

La tendance actuelle dans le domaine des télécommunications mène à des systèmes capables de fonctionner selon plusieurs standards, et donc plusieurs fréquences porteuses. La synthèse de la fréquence porteuse est un élément clef, dont les propriétés reposent essentiellement sur les performances de l’oscillateur employé. Pour assurer le fonctionnement de systèmes compatibles avec plusieurs standards de télécommunication, la solution conventionnelle consiste à intégrer plusieurs oscillateurs locaux. Cette solution est coûteuse, d’autant plus que, malgré le fait que les technologies actuelles atteignent des niveaux d’intégration très importants, la surface occupée par des oscillateurs traditionnels de type LC ne peut pas être diminuée, alors que le coût de fabrication au millimètre carré devient de plus en plus élevé. Il serait donc très intéressant de remplacer les oscillateurs LC, ce qui nous amène à rechercher des solutions alternatives parmi de nouvelles technologies. L’oscillateur spintronique (STO) est un nouveau dispositif issu des études sur les couches minces magnétiques. Il apparait comme un candidat potentiel de remplacement des oscillateurs LC du fait de sa grande accordabilité en fréquence et de son faible encombrement. Toutefois des mesures effectuées sur les STOs ont montré que la performance en puissance et en bruit de phase d’un oscillateur seul ne permet pas de remplir les spécifications pour des applications de télécommunication. Nous proposons de remplir ces spécifications en couplant un nombre d’oscillateurs spintroniques important. Dans ce cadre se posent plusieurs questions qui concernent les procédures de modélisation, d’analyse et de synthèse des systèmes interconnectés. Les procédures de modélisation incluent la démarche de recherche de modèles à complexité croissante qui décrivent les propriétés entrée-sortie d’un oscillateur spintronique, ainsi que la démarche de généralisation des modèles des oscillateurs dans le cadre du réseau. Les procédures d’analyse cherchent à vérifier la stabilité et évaluer la performance des systèmes interconnectés. Les procédures de synthèse permettent de concevoir des interconnexions sophistiquées pour les oscillateurs afin d’assurer toutes les spécifications du cahier des charges. Dans ce document, nous établissons tout d’abord le problème de la synthèse de fréquence par couplage avec un cahier des charges formalisé en termes de gabarits fréquentiels sur des densités spectrales de puissance. Le cahier des charges posé amène la nécessité de modéliser l’oscillateur spintronique pour pouvoir simuler et analyser son comportement. Ici, nous proposons une modélisation originale selon des degrés de complexité croissante. Ensuite, nous discutons de la structure de la commande de l’ensemble des oscillateurs afin de remplir les spécifications du cahier des charges. La structure de commande proposée nécessite de développer une méthode de conception des interconnexions du réseau d’après les critères de performance. Dans les deux derniers chapitres, nous proposons deux méthodes fréquentielles de synthèse originales pour résoudre le problème de synthèse de fréquence par couplage. La première méthode de synthèse permet de prendre en compte un critère mathématique du cahier des charges, qui correspond à un gabarit fréquentiel à respecter, et permet d’obtenir une matrice d’interconnexion des sous-systèmes, telle que le module de la réponse fréquentielle du réseau approxime le gabarit imposé par le cahier des charges. La deuxième méthode de synthèse permet de prendre en compte plusieurs gabarits fréquentiels à la fois. La solution obtenue est une matrice d’interconnexion des sous-systèmes, qui résout le problème de la synthèse de fréquence par couplage d’oscillateurs spintroniques. / The current trends in telecommunication are leading to systems that are compatible with multiple standards and consequently multiple carrier frequencies. The frequency synthesis is a key element influenced by the local oscillator performance. In order to ensure the system compatibility with multiple telecommunication standards, the conventional solution consists in using one local oscillator for each standard. This solution is expensive, even more, since the cost per squared millimetre is increasing, while the silicon area occupied by the traditional LC-tank oscillators cannot be reduced in spite of the fact that technology is going to higher integration levels. Thus, it should be interesting to find a substitution to the LC-tank oscillators which leads to research for alternative solutions among new technologies. The spin torque oscillator (STO) is a new device issued from the ferromagnetic thin-film research. Due to its frequency accord ability and its capability to occupy relatively small volume, it appears as a potential candidate for the LC-tank oscillator replacement. However, a set of measurements prove that these devices exhibit poor power and phase noise performance, making them unable to fulfill the technical specification of the radiofrequency applications. We propose to reach these specifications by coupling of a large number of spin torque oscillators. In this scope, numerous questions appear regarding the procedures of modelling, analysis and synthesis of the complex interconnected systems. The modelling procedures are dedicated to the increasing complexity models that describe the input-output behaviour of a spin torque oscillator and its behaviour within the interconnected network. The analysis procedures are targeted to verify the stability and to evaluate the performance level of the interconnected systems. The synthesis procedures allow to design the interconnection law for spin torque oscillators in order to fulfill the technical requirements. In this document, the frequency synthesis problem by spin torque oscillator coupling with technical specification description in terms of power spectral densities is established. The formulated specifications introduce the problem of the oscillator modelling in order to perform a simulation and an analysis of the oscillator behaviour. Here, we propose an original model using several conventional models with increasing complexity. An original oscillator network model that describes qualitative properties of the oscillator synchronisation is introduced. Afterwards, the control law architecture for an oscillator set is established in order to accomplish the technical requirement specifications. The suggested control architecture needs to be developed with quantitative systematic and efficient design method for the network interconnection taking into account the formulated performance criteria. In the last two chapters we propose two original frequency domain design methods allowing the resolution of our frequency synthesis problem. The first design method allows to consider explicitly a performance criterium corresponding toa desired frequency constraint. The method allows to obtain a suitable sub-system interconnection matrix that fits the frequency specification constraint. The second design method allows to find an interconnection matrix and to take into account simultaneously several frequency specification constraints. The interconnection matrix obtained with the proposed method solves the problem of frequency synthesis by coupling of spin torque oscillators.

[pt] Com a crescente demanda por maior capacidade na transmissão de dados, uma solução tem sido estudada para transmissão de rádio sobre fibra combinando múltiplos canais de dados sobre a portadora óptica na rede de acesso baseada em multiplexação por sub-portadoras. Ademais, essa rede de acesso é comumente ramificada na forma de uma rede óptica passiva. Monitoramento desses enlaces em fibra é, então, cada vez mais importante. A tecnologia atual de reflectometria óptica no domínio do tempo utilizada para monitoramento opera em um comprimento de onda óptico separado e possui ampla largura de banda de detecção, tornando-se relativamente cara. A busca por uma alternativa de monitoramento de alta precisão e baixo custo é de suma importância para a oferta de transmissão com garantia de qualidade de serviço. Neste trabalho, o uso de multiplexação por sub-portadoras é explorado, incorporando uma técnica de monitoramento de varredura de tom de baixa frequência na transmissão de dados. Um modelo matemático para a resposta em frequência do enlace foi derivado e a localização e a intensidade de uma falha são estimadas através da comparação com a amplitude e a fase detectadas da luz retroespalhadaa medida em que é feita uma varredura de frequência do sinal de monitoramento, aplicando-se um algoritmo de minimos quadrados. O modelo proposto considera que a medida do enlace antes da ocorrência de uma falha é conhecida. Uma única falha nova pode então ser detectada com precisão e sua posição e intensidade são estimadas da maneira descrita. / [en] With ever growing demand for higher capacity in data transmission, a solution has been proposed for analog Radio over Fiber transmission, combining several data channels over the optical carrier in the access network using Sub-Carrier Multiplexing (SCM). Furthermore, this access network is often branched in the form of a passive optical network (PON). Monitoring such fiber links is thus increasingly important. Current optical time domain reflectometry (OTDR) technology used for monitoring operates at a separate optical wavelength and has wide bandwidth detection, making it relatively costly. The pursuit of a low cost, high precision monitoring alternative is of paramount importance for cost effective quality of service (QoS) improvement. In this work employment of SCM for data multiplexing is exploited embedding a low frequency tone sweep monitoring technique into data transmission. A mathematical model for the frequency response of the link was derived and the fault location and intensity is estimated through comparison with acquired amplitude and phase of the backscattered light for the varying frequency by applying a simple least mean squared (LMS) algorithm. The modeling suggested requires that measurement of the link prior to the occurrence of a fault is known. A single new fault can then be accurately detected and its position and intensity estimated in the way described.