Dissertationen: „Near field magnetic enhancement“

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Beneš, Adam. „Plazmonické antény pro vysoké vlnové délky“. Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443226.

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Tato diplomová práce se zabývá vlastnostmi plazmonických antén v oblasti vysokých vlnových délek. Důraz je kladen na popis rezonančních vlastností jednotlivých antén i antén uspořádaných do periodických polí. Těžiště práce spočívá v počítačovém modelování navýšení magnetického pole v blízkosti antén, které lze využít ve vysokofrekvenční elektronové paramagnetické rezonanci (HFEPR) k zesílení měřeného signálu. Autor se zabývá kvantifikací zesílení v anténách s odlišnou geometrií a navrhuje i geometrii vlastní. Značná část práce se také věnuje snaze rozlišit příspěvky k navýšení magnetického pole od různých zdrojů při měření HFEPR v uspořádání s dvojitou transmisí záření.

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Sulaiman, Ali Haidar. „The near-Saturn magnetic field environment“. Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/44209.

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Shock waves exist throughout the universe and are fundamental to understanding the nature of collisionless plasmas. The complex coupling between charged particles and electromagnetic fields in plasmas give rise to a whole host of mechanisms for dissipation and heating across shock waves, particularly at high Mach numbers. While ongoing studies have investigated these process extensively both theoretically and via simulations, their observations remain few and far between. This thesis presents a study of very high Mach number shocks in a parameter space that has been poorly explored and identifies reformation using in situ magnetic field observations from the Cassini spacecraft at Saturn's bow shock. This gives an insight into quasi-perpendicular shocks across two orders of magnitude in Alfvén Mach number (MA) and spanning Earth-like to Astrophysical-like regimes. The work here shows evidence for cyclic reformation controlled by specular ion reflection occurring at the predicted timescale of ~0.3 τc, where τc is the ion gyroperiod. The relationship between these reformation signatures, magnetic overshoot and variability are also presented. The final part of this thesis characterises the region downstream of Saturn's bow shock, the magnetosheath. The results show a comprehensive overview of the configuration of the magnetic field in a non-axisymmetric magnetosheath. This non-axisymmetry is revealed to have an impact in the rotation of the magnetic field and is significant enough to influence the magnetic shear at the magnetopause.

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Séguin, Guy. „Enhancement of efficiency and accuracy of near-field measurements“. Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=35612.

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This thesis examines the possibility of increasing the speed of Near-Field measurement of an Antenna, by reducing the number of measurement points and by determining the degree of truncation permissible while maintaining a prescribed degree of precision of the reconstructed far-field.
The mathematical formulation leading to the near-field to far-field transform is presented in a novel and simpler form to use. Relations are established between the selected area and sampling rate of Near-Field measurement and the accuracy of the Far-Field of an Antenna. The spectral domain of the field is analysed in each case and parametric curves are derived. Correction of the spectral domain can significantly improve the accuracy of the Far-Field while using the same amount of Near-Field data.
A new concept, described as the Signature Function, is presented, analysed and tested. This new concept offers the possibility of conducting a highly reduced set of measurements while producing accurate results for antennas whose "Signature Function" is previously determined or can be estimated.
The simulated Near-Field of a radiating array is analysed in depth. A formulation and a procedure to correct the spectral domain of the field are established.
The technique developed is applied to experimental and simulated Near-Field data of large radiating Antennas leading to new information about the accuracy and speed of measurement achievable.

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Seguin, Guy. „Enhancement of efficiency and accuracy of near-field measurements“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0018/NQ44576.pdf.

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5

Fischer, Janina [Verfasser]. „Near-field mediated enhancement effects on plasmonic nanostructures / Janina Fischer“. Mainz : Universitätsbibliothek Mainz, 2012. http://d-nb.info/1019193654/34.

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6

Hearn, Christian Windsor. „Electrically-Small Antenna Performance Enhancement for Near-Field Detuning Environments“. Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/49554.

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Bandwidth enhancement of low-profile omnidirectional, electrically-small antennas has evolved from the design and construction of AM transmitter towers eighty years ago to current market demand for battery-powered personal communication devices. Electrically-small antenna theory developed with well-known approximations for characterizing radiation properties of antenna structures that are fractions of the radiansphere. Current state-of-the-art wideband small antennas near kaH1 have achieved multiple-octave impedance bandwidths when utilizing volume-efficient designs.
Significant advances in both the power and miniaturization of microelectronics have created a second possible approach to enhance bandwidth. Frequency agility, via switch tuning of reconfigurable structures, offers the possibility of the direct integration of high-speed electronics to the antenna structure. The potential result would provide a means to translate a narrow instantaneous bandwidth across a wider operating bandwidth.
One objective of the research was to create a direct comparison of the passive- multi-resonant and active-reconfigurable approaches to enhance bandwidth. Typically, volume-efficient, wideband antennas are unattractive candidates for low-profile applications and conversely, active electronics integrated directly antenna elements continue to introduce problematic loss mechanisms at the proof-of-concept level.
The dissertation presents an analysis method for wide bandwidth self-resonant antennas that exist in the 0.5dkad1.0 range. The combined approach utilizes the quality factor extracted directly from impedance response data in addition to near-and-far field modal analyses. Examples from several classes of antennas investigated are presented with practical boundary conditions. The resultant radiation properties of these antenna-finite ground plane systems are characterized by an appreciable percentage of radiated power outside the lowest-order mode.
Volume-efficient structures and non-omnidirectional radiation characteristics are generally not viable for portable devices. Several examples of passive structures, representing different antenna classes are investigated. A PIN diode, switch-tuned low-profile antenna prototype was also developed for the comparison which demonstrated excessive loss in the physical prototype.
Lastly, a passive, low-profile multi-resonant antenna element with monopole radiation is introduced. The structure is an extension of the planar inverted-F antenna with the addition of a capacitance-coupled parasitic to enhance reliable operation in unknown environments.

Ph. D.

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Went, Daniel Robert. „Magnetic field and plasma in Saturn's near space environment“. Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/9066.

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This thesis concerns spacecraft observations of magnetic field and plasma in Saturn’s near space environment and compares these observations with those made in and near the Jovian magnetosphere. Such comparisons are equivalent to ‘turning the experimental dial’ in planetary magnetospheres and provide a valuable insight into the way different parameters govern the structure and dynamics of magnetospheres throughout the solar system. Saturn and its magnetosphere is currently being studied by the Cassini spacecraft which, arriving at Saturn in the summer of 2004, became the first spacecraft ever to enter orbit around the planet. As a result there has never been a better time to study the Saturn system and the vast majority of the data utilized in this thesis were obtained by the Cassini spacecraft and its onboard instrumentation. Additional data were also obtained from the Pioneer, Voyager, Ulysses and Galileo spacecraft. Chapter 1 provides a general overview of space plasma and magnetospheric physics while Chapter 2 discusses the Saturn system in more detail. Chapter 3 describes the spacecraft and instrumentation used in this thesis with particular emphasis placed on magnetometer instruments and the Cassini-Huygens spacecraft. Chapter 4 compares the structure of Jupiter’s and Saturn’s outer magnetospheres and discusses the similarities and differences between the two. Chapter 5 presents a new empirical model of Saturn’s dayside bow shock and discusses the three dimensional shape of this surface while, finally, Chapter 6 presents observations of a magnetic cavity in the Saturnian magnetosphere which, as of writing, has yet to be explained. Chapter 7 summarises and concludes the thesis. The three independent investigations described above each shed light on a different aspect of Saturn’s magnetospheric structure and dynamics and contributes to an improved understanding of magnetospheric physics in general.

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Arkeholt, Simon. „Induction in Printed Circuit Boards using Magnetic Near-Field Transmissions“. Thesis, Linköpings universitet, Teoretisk Fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-148788.

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In 1865 Maxwell outlined the theoretical framework for electromagnetic field propagation. Since then many important developments have been made in the field, with an emphasis on systems using high frequencies for long-range interactions. It was not until recent years that applications based on short-range inductive coupling demonstrated the advantages of using low frequency transmissions with magnetic fields to transfer power and information. This thesis investigates magnetic transmissions in the near-field and the possibility of producing induced voltages in printed circuit boards. A near-field magnetic induction system is designed to generate a magnetic flux in the very low frequency region, and used experimentally to evaluate circuit board induction in several interesting environments. The resulting voltages are measured with digital signal processing techniques, using Welch’s method to estimate the spectrum of the received voltage signal. The results show that the amount of induced voltage is proportional to the inverse cube of the transmission distance, and that the system is able to achieve a maximum induced voltage of 65 \micro V at a distance of 2.5 m and under line-of-sight conditions. It is also concluded that conductive obstructions, electromagnetic shielding and background noise all have a large impact on the obtained voltage, either cancelling the signal or causing it to fluctuate.

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Bocan, Jiri. „Sensitivity enhancement and field-dependent relaxation in singlet nuclear magnetic resonance“. Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/354550/.

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Nitrous oxide (N2O), also known as "laughing" gas, is a well known compound used in medicine as a mild anaesthetic, or in engineering as a powerful oxidizer providing highoutput of engines. Recently, its 15N doubly-labelled isotopologue attracted attention in singlet NMR due to its long singlet relaxation time ranging between 7 minutes, when dissolved in blood, up to 26 minutes in degassed dimethyl sulfoxide (DMSO). Singlet NMR deals with nuclear singlet states, which are exchange antisymmetric quantum states of coupled pairs of spin-1/2 nuclei with zero total nuclear spin quantum number. These states are nonmagnetic and immune to exchange-symmetric relaxation processes such as intramolecular direct dipolar relaxation. Their lifetimes may be up to an order of magnitude longer than conventional relaxation times T1 and T2. Besides various fields of NMR, singlet states find potential application also in MRI. The direct medical application of 15N2O as a MRI tracer is, however, complicated by a poor detection sensitivity resulting from the low 15N magnetogyric ratio, low solubility in liquids at room temperature and atmospheric pressure, and limitations of 15N signal enhancement by means of physical methods for dissolved 15N2O. This thesis addresses two topics related to singlet NMR of 15N2O { sensitivity enhancement and magnetic-field dependent relaxation. The NMR signal decay in liquid phase is often dominated by static magnetic �eld inhomogeneity, described by the time constantT�2 , which is much faster than the transverse relaxation, characterized by T2. Repeated refocusing by a multiple spin-echo (MSE) train maintains the 15N signal for extended times of several T2. Acquisition of the signal during the whole MSE sequence followed by a proper processing either by matched weighting or singular value decomposition, may lead to the signal-to noise ratio (SNR) enhancement by up to an order of magnitude under favourable circumstances. The SNR enhancement is a function of T2, T� 2, and the spectral resolution. The procedure of the SNR enhancement in combination with methods of singlet NMR was used to investigate in detail low-field 15N2O singlet relaxation. The 15N2O relaxation measurements were extended to field strengths up to the spectrometer high field. The observed relaxation dependencies were described by a general theory, relaxation as a time-dependent exchange of populations of the �eld-dependent energy eigenstates. In particular, spin-rotation relaxation in low field was discussed.

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Shu, Qingying. „Statistical modelling of the near-Earth magnetic field in space weather“. Thesis, University of Glasgow, 2018. http://theses.gla.ac.uk/8937/.

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Space weather refers to electromagnetic disturbances in the near-Earth environment as a result of the Sun-Earth interaction. Severe space weather events such as magnetic storms can cause disruption to a wide range of technologies and infrastructure, including communications systems, electronic circuits and power grids. Because of its high potential impact, space weather has been included in the UK National Risk Register since 2011. Space weather monitoring and early magnetic storm detection can be used to mitigate risk in sensitive technological systems. The aim of this project is to investigate the electromagnetic disturbances in the near-Earth environment through developing statistical models that quantifies the variations and uncertainties in the near-Earth magnetic field. Data of the near-Earth magnetic field arise from in-situ satellite measurements and computer model outputs. The Cluster II mission (Escoubet et al., 2001a) has four satellites that provide in-situ measurements of the near-Earth magnetic field at time-varying locations along their trajectories. The computer model consists of an internal part that calculates the magnetic field sourced from Earth itself and an external part that estimates the magnetic field resulting from the Sun-Earth interaction. These magnetic fields, termed as the internal field and the external field, add up to the total magnetic field. Numerical estimates of the internal field and the external field are obtained respectively from the IGRF-11 model (Finlay et al., 2010) and the Tysganenko-96 (T96) model (Tsyganenko, 2013) given the times and the locations as inputs. The IGRF model outputs are invariant to space weather conditions whereas the T96 model outputs change with the input space weather parameters. The time-varying space weather parameters for T96 model include the solar wind ram pressure, the y and the z-components of the interplanetary magnetic field, and the disturbance storm time index. These parameters are the estimated time series of the solar wind conditions at the magnetopause, i.e. the boundary of the magnetosphere on the day-side, and the disturbance level at the Earth’s surface. Real-time values of the T96 model input parameters are available at hourly resolution from https://omniweb.gsfc.nasa.gov/. The overall aim of the thesis is to build spatio-temporal models that can be used to understand uncertainties and constraints leveraged from 3D mathematical models of space weather events. These spatio-temporal models can be then used to help understand the design parameters that need to be varied in building a precise and reliable sensor network. Chapter 1 provides an introduction to space weather in terms of the near-Earth magnetic field environment. Beginning with an overview of the near-Earth magnetic field environment, Chapter 2 describes the sources for generating in-situ satellite measurements and computer model outputs, namely the Cluster II mission, the IGRF model, and the T96 model. The process of sampling the magnetic field data from the different data sources and the space-time dependence in the hourly sampled magnetic field data are also included in this Chapter. Converting the space-time structure in the magnetic field data into a time series structure with a function relating the position in space to time, Chapter 3 explores the temporal variations in the sampled in-situ satellite measurements. Through a hierarchical approach, the satellite measurements are related to the computer model outputs. This chapter proposes statistical methods for dealing with the non-stationary features, temporal autocorrelation, and volatility present in the time series data. With the aim of better characterising the electromagnetic environment around the Earth, Chapter 4 develops time-series models of the near-Earth magnetic field utilising in-situ (CLUSTER) magnetic field data. Regression models linking the CLUSTER satellite observations and two physical models of the magnetic field (T96 and IGRF) are fit to each orbit in the period 2003-2013. The time series of model parameter estimates are then analysed to examine any long term patterns, variations and associations to storm indices. In addition to explaining how the two physical models calibrate with the observed satellite measurements, these statistical models capture the inherent volatility in the magnetic field, and allow us to identify other factors associated with the magnetic field variation, such as the relative position of each satellite relative to the Earth and the Sun. Mixed-effect models that include these factors are constructed for parameters estimated from the regression models for evaluating the performance of the two computer models. Following the calibration of the computer models against the satellite measurements, Chapter 5 investigates how these computer models allow us to investigate the association between the variations in near-Earth magnetic field and storms. To identify the signatures of storm onsets in different locations in the magnetosphere, change-point detection methods are considered for time series magnetic field signals generated from the computer models along various feasible satellite orbits. The detection results inform on potential sampling strategies of the near-Earth magnetic field to be predictive of storms through selecting achievable satellite orbits for placing satellite sensors and detecting changes in the time series magnetic signals. Chapter 6 provides of a summary of the main finding within this thesis, identifies some limitations of the work carried out in the main chapters, and include a discussion of future research. An Appendix provides details of coordinate transformation for converting the time and position dependent magnetic field data into an appropriate coordinate system.

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Brown, Wayne. „Characterisation of low energy ions observed near and during the substorm expansion phase onset“. Thesis, University of Warwick, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302621.

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12

He, Weiping. „Characterizing near-field circuit board radiation using crossed electric and magnetic dipole sources“. Diss., Rolla, Mo. : Missouri University of Science and Technology, 2010. http://scholarsmine.mst.edu/thesis/pdf/He_09007dcc807256ca.pdf.

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Thesis (M.S.)--Missouri University of Science and Technology, 2010.
Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed Dec. 23, 2009). Includes bibliographical references (p. 60).

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Gottula, Ronald Brett. „Discrete-Time Implementation, Antenna Design, and MIMO for Near-Field Magnetic Induction Communications“. BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3324.

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Near-field magnetic induction (NFMI) is a short range wireless technology that uses loop antennas coupled by a magnetic field. NFMI antennas are electrically small and thus extremely inefficient and narrow band, making system design for multi-user and high-bitrate applications challenging. The goals of this thesis are to develop a test platform suitable for NFMI antenna testing, to model, design and test NFMI antennas that have high bandwidth-efficiency, and to explore the possibility of using MIMO (multiple-input multiple-output) to increase the capacity of the NFMI channel. This thesis provides system implementations, test results, and channel modeling to aid in the design of future NFMI systems. Implementation of a multi-channel discrete-time wireless system are provided for PC-based software and FPGA-based firmware as a platform for antenna testing. Optimized antenna designs in terms of efficiency and bandwidth are presented, achieving the theoretical bandwidth-efficiency bound for small antennas. Preliminary modeling and simulation results for the NFMI-MIMO channel are included, which show that the information-theoretic capacity of the NFMI-MIMO channel is approximately double the standard single-antenna NFMI capacity at 10 bits/s/Hz.

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Williams, Devin Wells. „Optimization of Near Field Coupling for Efficient Power Transfer Utilizing Multiple Coupling Structures“. Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/32933.

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A rise in the need for dynamic energy allocation has been associated with the saturation of available portable wireless electronic devices. Currently, the methods for transmitting this energy efficiently have been limited to a number of options, including near field resonant magnetic coupling. Previous research with mid-range (dâ 4r) wireless power transfer has resulted in coupling efficiencies of close to 40%. In order to increase efficiency in transfer a more directive transmission system was developed using a phased array. Coupling networks were used to shift the resonance of the coupling device, leading to a tightly coupled network by array phasing. Coupling networks for the phased array were optimized using a hybrid combination of a full wave Method of Moments simulation with circuit simulation. Results were validated in a full wave simulator, and field results were shown during resonance. S-parameter results show simulated transfer efficiencies of 70% (-1.5dB) for a phased array structure and 62.3% (-2.4dB) for a single feed structure. Single feed prototyping S-parameter results show coupling efficiencies of 25% (-5.9dB). All coupling measurements are at a distance 4r with reference to the largest transmitting coupler.
Master of Science

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Bechtel, Kyle A. „MAGNETIC RESONANCE IN THE PROXIMITY OF AN INSTABILITY: PERPENDICULAR RESONANCE IN PERMALLOY NEAR THE CRITICAL FIELD“. Oxford, Ohio : Miami University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=miami1250281122.

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Eichel, Rüdiger-Albert. „New concepts in two-dimensional pulse electron paramagnetic resonance spectroscopy : resolution enhancement by magnetic field modulation /“. Zürich : [s.n.], 2001. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=14394.

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Réal, Denis. „Theutilization of near-field techniques to enhance electro-magnetic side channel cryptanalysis : new attacks and countermeasures“. Rennes, INSA, 2010. http://www.theses.fr/2010ISAR0005.

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Un composant cryptographique ne se comporte pas comme coffre-fort : son activité interne échange via des média accessibles avec son environnement proche et lointain. Ainsi, l’écoute du rayonnement électromagnétique est une réelle menace. Combiner des informations indirectes à la cryptanalyse logique permet en effet d’accéder à des informations confidentielles. Cette vulnérabilité devient inquiétante, la cryptographie ayant envahi notre quotidien tout numérique. Le travail de notre thèse porte donc sur la mesure en champ proche du rayonnement produit par les composants électroniques. Plus précisément, nous montrons comment l’instant et le lieu où la logique fuit peuvent être estimés, même en présence de contre-mesures sur le signal d’horloge. Ces techniques de localisation spatiale et temporelle ont été expérimentées, toutes avec succès, sur plusieurs cibles implémentant divers algorithmes cryptographiques (le DES, l’AES ou le RSA). Les techniques développées permettent de retrouver des secrets même en présence de contre-mesures. Nous avons attaqué dans un premier temps la cryptographie asymétrique (RSA ou cryptographie sur courbes elliptiques), protégée en masquant par un aléa l’exposant privé. Ensuite est visée la dérivation de clé par hachage itératif (SHA1) pour la cryptographie symétrique. L’usage de ces contre-mesures est fréquent car elles sont bien maîtrisées et à bas coût. Dans les deux cas, après avoir localisé dans le temps et l’espace un objet compromettant, des méthodes de cryptanalyse logique adaptées à notre problématique ont permis d’aboutir. Nous nous sommes également intéressés à certain algorithmes symétrique confidentielles. Les polynômes de rebouclage et les schémas de Feistel ont été attaqués avec succès. Des contre-mesures qui permettent de ralentir ces attaques sont enfin proposées et discutées
A cryptographic device does not act as a strong-box: its internal activity emanates on media such as power consumption or execution time. Eavesdropping on electro-magnetic radiations is a real threat. Indeed, combining this indirect information with classical cryptanalysis makes confidential information available. Designers cannot turn a bind eye to this vulnerability: cryptographic applications are everywhere in our whole digital world. This thesis focuses on the radiations emitted by electronic devices. We show that the moment and the place where the logic leaks can be estimated precisely, even when designers add countermeasures on the ubiquitous clock signal. These techniques of localization in time and space have been tested with success some targets implementation different algorithms (DES, AES or RSA). The techniques developed enable to find out secrets even when countermeasures are implemented. We have attack asymmetric cryptography (RSA and Elliptic Curves Cryptography) protected with private exponent randomization. Then is targeted the key derivation process based on hash function (SHA1) for symmetric cryptography. These countermeasures are well controlled and low cost. For both of them, we are able first to localize (space and time) a secret dependent object. Then, tailoring classical cryptanalysis enables us to find secrets out. We also have been interested in two confidential symmetric ciphers. Linear Feedback Shift Registers in a Stream Cipher and a generic Feistel scheme are targeted with success. Countermeasures for slowing down attacks have been proposed and discussed

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Aizawa, Hirohito, Kazuhiko Kuroki und Yukio Tanaka. „Strong magnetic field enhancement of spin triplet pairing arising from coexisting 2k_F spin and 2k_F charge fluctuations“. American Physical Society, 2008. http://hdl.handle.net/2237/11284.

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Sivaraman, Nimisha. „Design of magnetic probes for near field measurements and the development of algorithms for the prediction of EMC“. Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAT082/document.

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Au fur et à mesure que le nombre de composants augmente, il existe une forte demande pour identifier les sources de rayonnement pour la prédiction de la compatibilité électromagnétique des circuits électroniques. Le balayage d’une sonde à proximité du circuit est une méthode générale d'identification des sources rayonnantes dans une PCB. La première partie de la thèse consiste à concevoir et à caractériser des sondes magnétiques à haute sensibilité et à haute résolution spatiale. Les sondes conventionnelles basées sur la ligne micro ruban et la configuration coplanaire sont étudiées. À mesure que la longueur de la ligne de transmission connectée à la sonde augmente, le bruit sur le signal de sortie augmente en raison de tensions de mode commun induites par le champ électrique. Afin de supprimer cette tension induite par le champ électrique, une sonde magnétique blindée est conçue et fabriquée à l'aide d'une technologie de circuit imprimé à faible coût (PCB). La performance de la sonde passive est validée dans la bande 1MHz - 1GHz. La sonde blindée est fabriquée sur un substrat FR4 d'une épaisseur de 0,8 mm et se compose de 3 couches avec le signal dans la couche intermédiaire et les couches supérieure et inférieure dédiées aux plans de masse. La taille d'ouverture de la boucle est de 800 μm x 800 μm, avec une résolution spatiale attendue de 400 μm. La haute sensibilité de la sonde est obtenue en intégrant un amplificateur à faible bruit à la sortie de la sonde, ce qui en fait une sonde active. La performance de la sonde blindée avec différentes longueurs de lignes de transmission est faite pour étudier. Une sonde à trois axes capable de mesurer les trois composantes du champ magnétique est également conçue et validée par un balayage en champs proches au-dessus d'une structure standard plan de masse.Dans la deuxième partie, la méthode de la matrice de la ligne de transmission inverse (Inv-TLM) est utilisée, pour reconstruire la distribution source à partir des champs proches (NFS) mesurés au-dessus d'un plan sur la carte PCB. Même si, la résolution de la reconstruction dépend de la longueur d'onde et des paramètres du maillage, la propagation inverse augmente la largeur de l'onde reconstruite. Comme cette méthode corresponde à un problème « mal posé» et entraîne des solutions multiples, nous avons développé une nouvelle méthode basée sur la corrélation croisée bidimensionnelle, qui représente les données de balayage en champ proche sous forme de de dipôles équivalents. Avec cette nouvelle méthode, nous avions pu identifier et de localiser les sources actuelles dans le PCB et est représenté avec des sources équivalentes. La méthode est validée pour les sources avec des orientations différentes. Les données simulées des champs proches utilisant le logiciel commercial CST sont utilisées pour valider les deux méthodes. Le champ lointain prédit à partir de ces sources équivalentes est comparé aux champs simulés
As the number of components in a confined volume is increasing, there is a strong demand for identifying the sources of radiation in PCBs and the prediction of EMC of electronic circuits. Electromagnetic near field scanning is a general method of identifying the radiating sources in a PCB. The first part of the thesis consists of the design and characterization of printed circuit magnetic probes with high sensitivity and high spatial resolution. Conventional probes based on microstrip and coplanar configuration is studied. As the length of the transmission line connected to the probe increases, the probe output contains noise due to common mode voltages which is many induced by the electric field. In order to suppress the voltage induced due to the electric field, a shielded magnetic probe is designed and fabricated using low cost printed circuit board (PCB) technology. The performance of the passive probe is calibrated and validated from 1MHz – 1GHz. The shielded probe is fabricated on an FR4 substrate of thickness 0.8mm and consists of 3 layers with the signal in the middle layer and top and bottom layers dedicated to ground planes. The aperture size of the loop is 800µm x 800µm, with an expected spatial resolution of 400 µm. The high sensitivity of the probe is achieved by integrating a low noise amplifier at the output of the probe, hence making an active probe. The performance of the shielded probe with a different length of transmission lines is made to study. When the probe has to be operated above 100MHz, it is found that the transmission lines connected to the probe should be short (around 1.5cmm). For frequencies below 100MH, the length of the lines can be up to 12cm. A three-axis probe which is able to measure the three components of the magnetic field is also designed and validated by near field scanning above a standard wire over the ground structure.In The second part, the inverse transmission line matrix method (Inv-TLM) method is used reconstruct the source distribution from the near field scan (NFS) data above a single in plane on the PCB. Even though the resolution of reconstruction depends on the wavelength and the mesh parameter, the inverse propagation increases the width of the reconstructed wave. As this method is found to be ill posed and results in multiple solutions, we have developed a new method based on the two-dimensional cross-correlation, which represents the near field scan data in terms of the equivalent electric currents of the dipole. With the new method, we are able to identify and locate the current sources in the PCB and are represented by an equivalent source. The method is validated for the current sources with different orientations. The simulated near field data using CST microwave studio is used to validate both the methods. The radiated far field from these equivalent sources is compared with the simulated fields

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Eftekhar, Ali Asghar. „Nanoscale light-matter interactions in the near-field of high-Q microresonators“. Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45900.

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The light-matter interaction in the near-field of high-Q resonators in SOI and SiN platforms is studied. The interactions of high-Q traveling-wave resonators with both resonant and non-resonant nanoparticles are studied and different applications based on this enhanced interactions in near-field such as high-resolution imaging of mode profile of high-Q resonators, label-free sensing, optical trapping, and SERS sensing are investigated. A near-field imaging system for the investigation of the near-field phenomena in the near-field of high-Q resonators is realized. A new technique for high-resolution imaging of the optical modes in high-Q resonators based on the near-field perturbation is developed that enables to achieve a very high resolution (< 10 nm) near-field image. The prospect of the high Q resonators on SOI platform for highly multiplexed label-free sensing and the effect of different phenomena such as the analyte drift and diffusion and the binding kinetics are studied. Also, the possibility of enhancing nanoparticle binding to the sensor surface using optical trapping is investigated and the dynamic of a nanoparticle in the high-Q resonator optical trap is studied. Furthermore, the interaction between a resonant nanoparticle with a high-Q microdisk resonator and its application for SERS sensing is studied. A model for interaction of resonant nanoparticles with high-Q resonators is developed and the optimal parameters for the design of coupled microdisk resonator and a plasmonic nanoparticle are calculated. The possible of resonant plasmonic nanoparticle trapping and alignment in an SiN microdisk resonator optical trap is also shown.

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Kopecký, Petr. „Automatizace měření EM pole měřičem Narda NBM-550“. Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-219160.

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The diploma thesis deals with the measurement of electromagnetic fields by the meter NARDA NBM 550. The aim of the paper is to introduce the possibilities of measurement of the electromagnetic field by this device, to study the feasibility of communication with computer, to create control program and to check its functionality. A description of the electromagnetic field properties is followed by the identification of the device main functions. Additionally, the operating program is described together with the draft of measuring workplace with its realization. The results of probationary measurements are presented in the end of the thesis.

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Van, Zyl Derrick Steven. „SQUID detected low-field NMR for the evaluation of internal fruit quality“. Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/5208.

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Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: Assessing the quality of fruit has become vitally important for farmers and growers. With retailers placing ever stricter requirements on fresh produce, growers have to spend a greater amount of time and effort sorting and grading their harvest. Increasingly, vendors are placing requirements not only on external factors like colour, and firmness, but on internal quality factors such as sugar content and acidity, because, although consumers buy fruit based on their external appearances, the taste of the fruit is what determines whether the consumer will buy again. Different techniques exist that probe the internal quality of fruit non-destructively. The technique most widely used today is Near Infrared Spectroscopy. This technique is powerful, but has certain limitations such as poor reliability and the need for constant recalibration. This thesis suggests an alternative method for evaluating internal fruit quality based on low-field nuclear magnetic resonance detected by superconducting quantum interference devices. It introduces the theory of SQUIDs and NMR, and evaluates the use of SQUID detected NMR spectroscopy as a method for determining the internal quality of fruit. The fabrication techniques and processes are explained in detail and a design for a SQUID detected NMR spectrometer is given. Relevant simulations and simulation results are also given. No working SQUID could be fabricated and, as such, no working NMR spectrometer was demonstrated. This thesis serves as a reference work for future research.
AFRIKAANSE OPSOMMING: Bepaling van die gehalte van vrugte het vir boere uiters belangrik geword. Met kleinhandelaars wat al strenger vereistes plaas op vars produkte moet boere meer tyd en inspanning bestee met die sortering en gradering van hul oes. Handelaars plaas nie net vereistes op eksterne kwaliteitsfaktore soos kleur en fermheid nie, maar begin al hoe strenger vereistes plaas op interne kwaliteitsfaktore soos suikerinhoud en suurgehalte, want, hoewel verbruikers vrugte koop op grond van hul eksterne kwaliteitsfaktore, is dit die smaak van die vrug wat bepaal of die verbruiker weer die vrug sal koop. Verskillende tegnieke bestaan wat die interne kwaliteit van vrugte op ’n nie-destruktiewe manier kan bepaal. Die mees algemene tegniek is Naby Infrarooi Spektroskopie. Hierdie tegniek is kragtig maar het sekere beperkings soos swak betroubaarheid en die noodsaaklikheid van konstante herkalibrasie. Hierdie tesis stel ’n alternatiewe metode vir die evaluering van interne vrugkwaliteit gebaseer op lae-veld kernmagnetiese resonans waargeneem deur supergeleidende kwantum inmenging toestelle voor. Dit stel die teorie van SKWITs en KMR bekend, en evalueer die gebruik van SKWIT-bespeurde KMR spektroskopie as ’n metode vir die bepaling van die interne kwaliteit van vrugte. Die fabrikasie tegnieke en prosesse word in detail verduidelik en ’n ontwerp vir ’n SWKIT opgevangde KMR spektrometer word gegee. Toepaslike simulasies en simulasie resultate word ook gegee. Geen werkende SKWIT kon vervaardig word nie en as gevolg daarvan kon geen werkende KMR spektrometer gedemonstreer word nie. Hierdie tesis dien as ’n naslaan werk vir toekomstige navorsing.

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Olk, Phillip. „Optical Properties of Individual Nano-Sized Gold Particle Pairs“. Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1218612352686-00553.

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This thesis examines and exploits the optical properties of pairs of MNPs. Pairs of MNPs offer two further parameters not existent at single MNPs, which both affect the local optical fields in their vicinity: the distance between them, and their relative orientation with respect to the polarisation of the excitation light. These properties are subject of three chapters: One section examines the distance-dependent and orientation-sensitive scattering cross section (SCS) of two equally sized MNPs. Both near- and far-field interactions affect the spectral position and spectral width of the SCS. Far-field coupling affects the SCS even in such a way that a two-particle system may show both a blue- and redshifted SCS, depending only on the distance between the two MNPs. The maximum distance for this effect is the coherence length of the illumination source – a fact of importance for SCS-based experiments using laser sources. Another part of this thesis examines the near-field between two MNPs and the dependence of the locally enhanced field on the relative particle orientation with respect to the polarisation of the excitation light. To attain a figure of merit, the intensity of fluorescence light from dye molecules in the surrounding medium was measured at various directions of polarisation. The field enhancement was turned into fluorescence enhancement, even providing a means for sensing the presence of very small MNPs of 12 nm in diameter. In order to quantify the near-field experimentally, a different technique is devised in a third section of this thesis – scanning particle-enhanced Raman microscopy (SPRM). This device comprises a scanning probe carrying an MNP which in turn is coated with a molecule of known Raman signature. By manoeuvring this outfit MNP into the vicinity of an illuminated second MNP and by measuring the Raman signal intensity, a spatial mapping of the field enhancement was possible
Diese Dissertation untersucht und nutzt die optischen Eigenschaften von Paaren von Metall-Nanopartikeln (MNP). MNP-Paare bieten gegenüber einzelnen MNP zwei weitere Parameter, welche beide auf das optische Nahfeld der zwei MNPs wirken: zum Einen der Abstand der zwei MNPs zueinander, zum Anderen die relative Ausrichtung des Paares bezüglich der Polarisation des anregenden Lichts. Diese Eigenschaften sind Thema der Arbeit: Ein Abschnitt untersucht den abstands- und orientierungsabhängigen Streuquerschnitt (SQS) zweier gleichgroßer MNPs. Die spektrale Position und die Breite des SQS wird von Wechselwirkungen sowohl im Nah- als auch im Fernfeld beeinflusst. Der Einfluß der Fernfeld-Wechselwirkung geht so weit, daß ein Zwei-MNP-System sowohl einen blau- als auch einen rotverschobenen SQS haben kann – dies hängt lediglich vom Abstand der zwei MNPs ab. Die Reichweite dieser Fernfeld-Wechselwirkung wird durch die Kohärenzlänge der Beleuchtungsquelle bestimmt – eine wichtige Tatsache für SQS-Untersuchungen, welche Laserquellen verwenden. Ein weiterer Teil der Dissertation untersucht das Nahfeld zwischen zwei MNPs. Insbesondere wird dargestellt, inwieweit die Überhöhung des Nahfelds von der Orientierung des Partikelpaares bezüglich der Polarisation des Anregungslichts abhängt. Um den Effekt quantifizieren zu können, wurde die Intensität der Fluoreszenz des umgebenden Mediums für verschiedene Polarisationsrichtungen gemessen. Die lokale Feldverstärkung konnte in eine Fluoreszenzverstärkung gewandelt werden, mit deren Hilfe sich sogar die Anwesenheit sehr kleiner MNPs von nur 12 nm Durchmesser nachweisen ließ. Wie Nahfeld-Intensitäten experimentell quantifiziert werden können, stellt ein dritter Abschnitt dieser Dissertation vor – per MNP-verstärkter Raman-Rastersonden-Mikroskopie. Diese Technik besteht aus einer Rastersonde, welcher ein MNP anheftet, welches wiederum mit einem Molekül bekannter Ramansignatur überzogen ist. Indem solch eine Sonde in die unmittelbare Nähe eines zweiten, beleuchteten MNPs gebracht wurde und dabei die Intensität des Raman-Signals aufgezeichnet wurde, ließ sich die räumliche Verteilung der Ramanverstärkung vermessen

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Daiki, Mossaab. „Contribution au développement d’antennes lecteurs champ proche pour les systèmes RFID UHF passifs“. Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GRENT020/document.

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La RFID est une technologie majeure qui connaît depuis plus d'une dizaine d'années un essor considérable en termes d'applications. Cependant son déploiement à grande échelle reste limité par des plusieurs verrous technique et technologique par lesquels la portée de lecture des tags et leur forte sensibilité à l'environnement de l'application. Le travail engagé dans cette thèse vise le développement des nouvelles antennes lecteurs pour systèmes RFID UHF champ proche. Ce type de système exploite la bande UHF de la RFID en zone de champ proche pour la traçabilité des cibles de taille miniature sur une zone proche du lecteur avec une portée limitée. Les tags se trouvant au delà de cette portée ne doivent pas être détectés par le lecteur. L'objectif dans ce travail est d'apporter des solutions au niveau des antennes lecteurs également celles du tag pour assurer une détection des tags sur une zone confinée de l'espace. Actuellement, moyennant l'utilisation d'un tag sous forme de boucle (1*1 cm²), il est possible de lire ce dernier en contact, c'est à dire dans la zone 0 – 10 cm. Il fallait donc pouvoir assurer une lecture fiable (de type couplage EM) pour une portée s'étendant d'une dizaine de centimètres. Les antennes lecteurs champ proche développés dans ce travail sont en mesure d'assurer une zone de lecture limitée (20 à 35 cm) qui s'étend sur une dizaine de centimètres de côté
RFID is one of the most popular technologies in this decade. However, its deployment at a high scale is limited by several technical and technological limitations as the read range of tags and their sensitivity to the application's environment. In this thesis we focus on the development of new reader antennas for Near Field UHF RFID systems. This type of system uses the UHF RFID band in near field zone for the traceability of miniature size targets on an area near the reader with a limited zone. Tags being outside this zone should not be detected by the reader .One of the objective of this thesis is to provide solutions in terms of readers and tag antennas to ensure detection tags on a confined area of space. Actually, we can read loop RFID tag (1*1 cm²) in contact (read range 0-10 cm). So we have to be able to ensure a good reading of tag (EM coupling) in a range from few centimeters to meters. Near field reader antenna developed in this thesis work, has a limited range between 20 and 30 cm with a large reading zone

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Halidi, El Mohamed. „Études RMN et IRM en champ proche : développements et applications“. Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20261/document.

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Le principe de la RMN repose sur la détection de l'aimantation provenant de spin des noyaux atomiques tels que 13C, 31P et 1H. L'échantillon est placé dans un champ magnétique statique, qui polarise l'ensemble des spins. Ces derniers sont ensuite excités par les impulsions radiofréquences (environ un mètre de longueur d'onde), qui font basculer l'aimantation de ces spins dans le plan transversal. Lorsque l'aimantation retourne à sa position d'équilibre, il génère un champ électromagnétique qui est classiquement détecté par une antenne réceptrice (bobine avec un circuit d'accord/d'adaptation) à couplage inductif. Dans ce travail, nous proposons l'utilisation d'une sonde de taille micrométrique placée au voisinage de l'objet d'intérêt, à une distance bien plus courte que la longueur d'onde du signal de RMN rayonné. Notre microsonde présente des caractéristiques innovantes (i) un couplage capacitif (composante du champ électrique), (ii) une dimension réduite pour un positionnement précis, qui assure la détection du signal de RMN de l'échantillon et (iii) une détection à large bande, ce qui permet de l'utiliser pour détecter différents noyaux sans être accordée à la fréquence de Larmor. Pour vous présenter cette nouvelle alternative, les outils nécessaires à la compréhension de ce travail, en l'occurrence le principe de la RMN et de l'IRM et une introduction de la théorie du champ proche électrique sont donnés. Nous avons fait aussi un état de l'art des méthodes et techniques existant pour mesurer le signal RMN afin de recenser les avantages qu'un tel système (méthode : couplage capacitif et dispositif : microsonde de champ proche) peut apporter à la technique RMN. Ensuite, nous avons caractérisé notre microsonde pour améliorer sa détection hyper localisée, nous avons démontré que le signal RMN récupéré par notre antenne peut être décrit par l'expression du champ proche électrique :E(x, z) = A(Kz ) exp(i(z/L)) exp(−x/L) + Terme Propagatif. Enfin, nous avons appliqué notre système à des études RMN comme la spectroscopie, la relaxométrie ou encore de l'imagerie RMN. Nous avons aussi énoncé certains projets potentiels à la continuité de ce travail
The principle of NMR is based on the detection of the magnetization originating from the spin of atomic nuclei such as 13C, 31P and 1H. The sample is placed in a static magnetic field, which polarizes the ensemble of spins and it is excited by radiofrequency pulses (wavelength about one meter), that tilt the axis of the magnetization. When the magnetization returns to equilibrium, it generates an electromagnetic field which is classically detected by a receiving antenna (coil with atuning/matching circuit) in inductive coupling.In this work, we propose the use of a micrometer-sized probe positioned in the vicinity of the object of interest, at a distance well shorter than the wavelength of the radiated NMR signal.Our microprobe presents innovative characteristics (i) a capacitive coupling (electric field component), (ii) reduced dimensions for an accurate positioning, which ensure the detection of NMR signal from the sample and (iii) it has a broadband, which allows use to detect any nuclei without being tuned to the Larmor frequency.To introduce you this new alternative, the tools necessary to the understanding of this work, in this case the principle of NMR/MRI and an introduction of the theory of the electric near field are given initially.We made also a state of the art of existing methods and techniques for measuring the NMR signal to identify the benefits that such a system (method : capacitive coupling and device : microprobe near field) can bring to the NMR technique.Then, we have characterized our microprobe to enhance its localized detection due to its small size (127 μm in diameter and 2mm in length). In this stage of characterization, we demonstrated that the NMR signal recovered by our antenna can be described by the electric near field expression :E(x, z) = A(Kz ) exp(i(z/L)) exp(−x/L) +Propagative TermFinally, we applied our system to make NMR studies such as spectroscopy, the relaxometry and NMR Imaging. We have outlined some potential projects to the continuity of this work

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Vogel, Michael Werner. „Theoretical and numerical investigation of plasmon nanofocusing in metallic tapered rods and grooves“. Queensland University of Technology, 2009. http://eprints.qut.edu.au/29241/.

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Effective focusing of electromagnetic (EM) energy to nanoscale regions is one of the major challenges in nano-photonics and plasmonics. The strong localization of the optical energy into regions much smaller than allowed by the diffraction limit, also called nanofocusing, offers promising applications in nano-sensor technology, nanofabrication, near-field optics or spectroscopy. One of the most promising solutions to the problem of efficient nanofocusing is related to surface plasmon propagation in metallic structures. Metallic tapered rods, commonly used as probes in near field microscopy and spectroscopy, are of a particular interest. They can provide very strong EM field enhancement at the tip due to surface plasmons (SP’s) propagating towards the tip of the tapered metal rod. A large number of studies have been devoted to the manufacturing process of tapered rods or tapered fibers coated by a metal film. On the other hand, structures such as metallic V-grooves or metal wedges can also provide strong electric field enhancements but manufacturing of these structures is still a challenge. It has been shown, however, that the attainable electric field enhancement at the apex in the V-groove is higher than at the tip of a metal tapered rod when the dissipation level in the metal is strong. Metallic V-grooves also have very promising characteristics as plasmonic waveguides. This thesis will present a thorough theoretical and numerical investigation of nanofocusing during plasmon propagation along a metal tapered rod and into a metallic V-groove. Optimal structural parameters including optimal taper angle, taper length and shape of the taper are determined in order to achieve maximum field enhancement factors at the tip of the nanofocusing structure. An analytical investigation of plasmon nanofocusing by metal tapered rods is carried out by means of the geometric optics approximation (GOA), which is also called adiabatic nanofocusing. However, GOA is applicable only for analysing tapered structures with small taper angles and without considering a terminating tip structure in order to neglect reflections. Rigorous numerical methods are employed for analysing non-adiabatic nanofocusing, by tapered rod and V-grooves with larger taper angles and with a rounded tip. These structures cannot be studied by analytical methods due to the presence of reflected waves from the taper section, the tip and also from (artificial) computational boundaries. A new method is introduced to combine the advantages of GOA and rigorous numerical methods in order to reduce significantly the use of computational resources and yet achieve accurate results for the analysis of large tapered structures, within reasonable calculation time. Detailed comparison between GOA and rigorous numerical methods will be carried out in order to find the critical taper angle of the tapered structures at which GOA is still applicable. It will be demonstrated that optimal taper angles, at which maximum field enhancements occur, coincide with the critical angles, at which GOA is still applicable. It will be shown that the applicability of GOA can be substantially expanded to include structures which could be analysed previously by numerical methods only. The influence of the rounded tip, the taper angle and the role of dissipation onto the plasmon field distribution along the tapered rod and near the tip will be analysed analytically and numerically in detail. It will be demonstrated that electric field enhancement factors of up to ~ 2500 within nanoscale regions are predicted. These are sufficient, for instance, to detect single molecules using surface enhanced Raman spectroscopy (SERS) with the tip of a tapered rod, an approach also known as tip enhanced Raman spectroscopy or TERS. The results obtained in this project will be important for applications for which strong local field enhancement factors are crucial for the performance of devices such as near field microscopes or spectroscopy. The optimal design of nanofocusing structures, at which the delivery of electromagnetic energy to the nanometer region is most efficient, will lead to new applications in near field sensors, near field measuring technology, or generation of nanometer sized energy sources. This includes: applications in tip enhanced Raman spectroscopy (TERS); manipulation of nanoparticles and molecules; efficient coupling of optical energy into and out of plasmonic circuits; second harmonic generation in non-linear optics; or delivery of energy to quantum dots, for instance, for quantum computations.

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Manseur, Megdouda. „Contribution à l’étude d’un système de biotélémesure intracorporelle par gélule ingérable“. Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14430/document.

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Cette thèse est une contribution à l’étude d’un système de biotélémesure par gélule ingérable. L’étude concerne les problèmes de télétransmission d’énergie et d’informations entre la gélule ingérable et le système extracorporel de télécommande.Nous exposons des méthodes de conception théoriques et de caractérisation expérimentales du système de télécommande sans fil de la mise sous tension des gélules. Une deuxième partie concerne la conception du système de télétransmission d’énergie et d’informations par induction magnétique, suivi de la réalisation d’un système d’accord automatique par capacité commutée synchrone. La caractérisation d’antennes miniatures a fait l’objet d’une troisième partie dans laquelle nous avons proposé des solutions basées sur des techniques de mesure des paramètres Sij en différentiel.Enfin, nous présentons la conception d’une sonde de champ magnétique destinée à valider les résultats de simulation
This thesis is a contribution to study of intracorporeal measure of ingestible capsule. It concerns more specifically the problems of wireless transmission of energy and information between the capsule and ingestible extracorporeal control and monitoring system. Thus we first set of design methods and theoretical characterization of the experimental system of wireless remote power up capsules. A second part was dedicated to wireless transmission of energy and information design through magnetic induction, it led to the creation of an original system of tuning by synchronous switched capacitor. The problem of miniature antennas characterization has been a third party in which we have proposed innovative solutions based on techniques for measuring parameters Sij in differential (or transmission). Finally, we presented in the last part the design and characterization of a magnetic field probe designed to validate the simulation results

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Schoenmaker, Jeroen. „Desenvolvimento de um microscópio óptico e magnetoóptico de varredura em campo-próximo“. Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-26052009-102436/.

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Para o desenvolvimento da nanociência atual há forte demanda por equipamentos capazes de caracterizar sistemas em escalas da ordem nanométrica. Este contexto impulsionou o desenvolvimento de microscópios ópticos de varredura em campopróximo (Scanning Near-field Optical Microscope SNOM). Diferentemente da microscopia óptica tradicional, os SNOMs detectam a radiação eletromagnética evanescente e, conseqüentemente, a resolução não é limitada pelo critério de Rayleigh. No Laboratório de Materiais Magnéticos IFUSP desenvolvemos um SNOM sensível a efeitos Kerr magnetoópticos (MO-SNOM). Dessa maneira, associamos a alta resolução da técnica à alta sensibilidade dos efeitos magnetoópticos. Trata-se se uma área relativamente pouco explorada e carente de resultados sistemáticos na literatura. Utilizando o MO-SNOM, caracterizamos partículas microestruturadas de Co70.4Fe4.6Si15B10 amorfo com dimensões de 16x16x0.08 microm3 e 4x4x0.08 microm3. Os resultados compreendem dezenas de imagens de susceptibilidade magnetoóptica diferencial com resolução melhor que 200 nm e curvas de histerese local. Em primeira análise, a demonstração de resultados sistemáticos ajuda a estabelecer a técnica. O comportamento magnético das partículas, estudadas sob várias condições de campo aplicado, se mostrou determinado basicamente pela anisotropia de forma. As curvas de histerese local mostraram comportamentos intrinsecamente locais e motivaram uma interessante discussão sobre os parâmetros de caracterização magnética convencionais. As medidas realizadas indicam que o efeito Kerr magnetoótico transversal em campopróximo é similar ao campo-distante. Os resultados são fortemente sustentados por medidas de microscopia magnetoóptica de campo-distante, simulações micromagnéticas e medidas de microscopia de força magnética. Medidas complementares revelam o potencial do MO-SNOM para caracterizações de objetos extensos quanto a potenciais de pinning. Além disso, medidas em filmes finos de NiFe/FeMn acoplados por exchange-bias evidenciam a alta sensibilidade do MO-SNOM, estimada de DM ~ 2 x 10-12 emu.
To support nanosciences evolution, there is a strong demand for developing new instrumentation devoted to nano-scale characterization. In this context, the development of the Scanning Near-field Optical Microscope (SNOM) took place. In contrast to traditional optical microscopes, SNOM deals with evanescent electromagnetic radiation and, consequently, the resolution is no longer limited by the Rayleigh criterion. At Laboratório de Materiais Magnéticos (LMM) IFUSP a SNOM devoted to magneto-optical Kerr effect measurements (MO-SNOM) has been developed. The MOSNOM associates the high resolution of the near-field technique to the high sensibility of the magneto-optical Kerr effect. Near-field magneto-optical microscopy is not yet wellestablished and there is a lack of systematic results in the literature. Using the MO-SNOM, amorphous Co70.4Fe4.6Si15B10 particles with 16x16x0.08 microm3 and 4x4x0.08 microm3 dimensions were studied. With resolution better than 200 nm, several magneto-optical differential susceptibility images and local hysteresis loops were obtained. The systematic results uphold the establishment of this new technique. Under the different applied field conditions, the magnetic behavior of the particles was found to be determined by shape anisotropy. Local hysteresis loops presented shapes intrinsic of local field induced process. The unusual hystesesis loops motivated interesting discussion about the conventional magnetic parameters. The MO-SNOM measurements indicate that the near-field transverse magneto-optical Kerr effect is similar to the far-field case. The results are highly supported by far-field magneto-optical microscopy, micromagnetic simulations and magnetic force microscopy measurements. Complementary measurements indicate the MO-SNOM potential to extensive magnetic surface characterization related to pinning potential distribution. Furthermore, measurements on the exchange-bias coupled NiFe/FeMn thin films make evident the MO-SNOM high sensitivity, estimated to be DeltaM ~ 2 x 10-12 emu.

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Hermany, Jiří. „Záření soustav antén v blízké zóně“. Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-217536.

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The aim of my diploma thesis is to analyze the antenna array radiation and to produce the antenna array radiation computation program. The program should display the electric and magnetic intensity and radiation power density distribution over the planar or cylindrical surface in the near-field area. The antenna array analyzed in this paper consists of a number of elementary dipoles placed in a row with a reflector which represents the conductive board situated in parallel to the row of dipoles. The demonstration program was built in MATLAB and allows computing and displaying the computed values components of antenna array radiation on the planar or the cylindrical surface. The program also allows saving computed values, saving displayed graphs, or saving the adjusted parameters of antenna array. The created program can be used for the presentation of the antenna array radiation in a school laboratory or for the graphical representation when a new antenna is designed.

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Ernandes, Cyrine. „Manipuler l'émission et l'absorption de transitions dipolaires magnétiques par l'utilisation de nano-antennes optiques“. Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS091.

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Au cours des dernières années, les progrès technologiques dans le domaine de la nanophotonique ont permis le développement des nanostructures optiques. Ces dernières possèdent la particularité de modifier l'émission lumineuse de nanoémetteurs quantiques .Cependant, l’interaction lumière-matière est considérée comme étant véhiculée par le champ électrique. Les études se sont alors concentrées sur le contrôle et la modification des propriétés d'excitation et d'émission des transitions dipolaires électriques.Récemment, il a été décrit qu’il existe dans la nature des nanoémetteurs possédant des transitions magnétiques détectables : ces nanoémetteurs sont les ions lanthanides.Les nanostructures optiques développant des résonances magnétiques pourraient alors modifier l’émission et l’excitation de transitions dipolaires magnétiques, de la même manière que leurs homologues électriques.Dernièrement , il a été démontré théoriquement que certain type de nanostructure, peuvent renforcer le champ magnétique optique par deux ordres de grandeur et qu’une fois couplé à un dipôle magnétique, ils peuvent augmenter fortement la fluorescence des transitions magnétiques comme celle qui que se trouve dans les ions de lanthanide.Une étude publiée dans Physical review letters, a rapporté qu’il était aussi possible d’étudier l’excitation de transitions dipolaires magnétiques.L’objectif de ma thèse a donc été d’utiliser certaines nanostructures ayant des affinités particulières avec le champ magnétique afin d’étudier et de manipuler l’émission et l'absorbption de transitions dipolaires magnétiques
During the last years, technological progresses in the field of nanophotonic have allowed the development of optical nanostructures to manipulate the emission of fluorescent nanoemitters . However, light-matter interactions are usually considered to be mediated by the optical electric field only, discarding the magnetic side of it. Indeed, most of the past studies have been only studying the modification of the excitation or emission properties of electric dipole transitions. Recently, it was demonstrated that magnetic dipole could also be found in lanthanide ions. It was also shown that by changing the magnetic local density of states near these ions, the emission fluorescent of the magnetic transitions could be enhanced or decreased with respect to their electric counterpart. In here, we demonstrate experimentally, in perfect agreement with numerical simulations, the manipulation of magnetic and electric dipolar transitions by means of plasmonic cavities. Using a near-field scanning optical microscope (NSOM), we bring in close proximity a nanoparticle doped with trivalent europium to plasmonic cavities of different sizes made of aluminum , allowing perfect control over the interactions between the emitter and the nanostructures. In this study, we show both an increase and decrease of electric and magnetic signal from the particle, and we also display the spatial distribution of both the electric and magnetic radiative local density of state at the surface of the cavities.Therefore, this work pave the way to the understanding of ‘magnetic light’ and matter interactions

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Legris, Michel. „Identification de l'état magnétique d'un système ferromagnétique à partir de mesures du champ proche“. Phd thesis, Grenoble INPG, 1996. http://tel.archives-ouvertes.fr/tel-00869936.

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Pour connaître l'état magnétique d'un objet complexe, bien souvent, la seule solution est de mesurer l'induction créée par la pièce en un nombre discret de points. La difficulté est alors de remonter à l'aimantation à partir de ces mesures. Une modélisation des * sources magnétiques est d'abord recherchée. La décomposition en harmoniques sphériques du champ mesurable ainsi que la recherche de dipôles normaux équivalents répartis sur la surface de l'objet sont étudiées. Leurs avantages et inconvénients étant très complémentaires, un nouveau modèle, synthèse des deux précédents, est proposé. Ensuite, l'utilisation d'un algorithme bayésien permet d'intégrer dans la projection de la mesure sur le modèle, les incertitudes et incohérences créées par l'imperfection de la mesure. En contrepartie, nous n'obtenons plus qu'un intervalle de confiance sur les valeurs recherchées. Enfin, une étude paramétrique analytique permet de connaître les performances du système. En particulier, le choix du type de capteurs de mesure est abordé.

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El, Hatmi Fatiha. „Conception d'antennes de communication à travers le corps humain pour le suivi thérapeutique“. Phd thesis, Université Paris-Est, 2013. http://tel.archives-ouvertes.fr/tel-00962121.

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Avec le développement rapide des technologies sans fil modernes et la miniaturisation des antennes et des systèmes électriques, l'emploi des antennes à l'intérieur du corps humain pour le suivi thérapeutique est devenu possible. Des batteries permettent d'alimenter ces antennes ; la réduction de la consommation de puissance implique l'augmentation de la durée de vie de circuits ingérables. Le corps humain, qui a une conductivité non nulle, n'est pas un milieu idéal pour la transmission des ondes RF à cause de l'atténuation liée aux propriétés diélectriques des tissus biologiques. Cependant, les tissus humains ne perturbent pas le champ magnétique car celui-ci dépend de la perméabilité du milieu qui est égale à un dans le corps humain. Bien que la puissance du champ magnétique décroisse avec l'exposant six de la distance, la technique utilisant les communications par induction magnétique en champ proche a été adoptée dans cette étude pour concevoir une liaison sans fil à faible portée à travers le corps humain. Durant ces travaux de thèse, après une caractérisation détaillée de la bobine d'émission située à l'intérieur du corps humain et de la bobine de réception localisée à sa surface, nous avons mis en place un bilan de liaison pour contribuer à l'amélioration du transfert de puissance dans ce milieu dissipatif. Un modèle analytique, déterminant les facteurs qui peuvent affecter le bilan de liaison par induction magnétique, a été vérifié à travers les simulations et les mesures. La variation de la position et de l'orientation de l'antenne ingérable ont été prises en compte pour évaluer la réponse de couplage entre la bobine émettrice et la bobine réceptrice. Les résultats obtenus constituent un pas en avant vers de futures recherches sur la conception de antennes dans les milieux dissipatifs et en particulier le corps humain

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Chipunga, Tichaona. „Channel capacity enhancement for a near field magnetic induction communication system“. 2010. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001331.

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M. Tech. Electrical Engineering.
The objective of this research is to model and simulate a high capacity and secure wireless communication protocol for personal area network. The high capacity of the system is achieved using Multiple Input Multiple Output (MIMO) technology while the security is ensured by using near field magnetic induction. The application targeted by this research confine to the military domain, where the confidentiality of the data exchanged is of prime importance. Computer simulations of MIMO application in near field magnetic induction communication were done and used to analyse the channel capacity Improvement. The outcome of the research contributes to the existing research in the near field magnetic induction communication by introducing a high capacity channel in near field magnetic induction communications.

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Qiu, Huan Ke, und 邱煥科. „Magnetic-field shielding characteristics in the near-field region“. Thesis, 1994. http://ndltd.ncl.edu.tw/handle/17352433038076103793.

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35

Boybay, Muhammed Said. „Sensitivity Enhancement of Near Field Probes Using Negative Materials“. Thesis, 2009. http://hdl.handle.net/10012/4597.

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In the last decade, design and application of negative materials have been one of the most interesting subjects in the electromagnetic research. The extraordinary properties of double negative (DNG) and single negative (SNG) materials have been studied extensively over this period. In this thesis, one of the unusual properties of negative materials, the evanescent amplification, is used to improve the sensitivity of the near field probes. The effect of placing DNG and SNG layers between the near field probes and the targets are investigated theoretically. A sensitivity definition is introduced for evanescent probes and it is shown using quantitative measures that the sensitivity can be increased using DNG and SNG materials for a target in vacuum and for a buried target. The electromagnetic loss of the negative materials and the mismatch between the material properties of the host medium and DNG and SNG materials are studied. Using an unmatched DNG layer or SNG layer enhances the sensitivity within an evanescent spectrum range while a lossless and matched DNG layer improves the sensitivity of entire evanescent spectrum. The idea of using negative materials is implemented over conventional near field probes by numerical experiments. Sensitivities of open-ended waveguides and open-ended coaxial lines for a specific application are studied in the presence of negative materials. In the case of precursor pitting detection on airplane bodies, the sensitivity of an open-ended waveguide probe is increased by 35 times for a λ/10 sized cubic crack. It is also shown that the negative material increases the quality of the image generated by the probe. The sensitivity improvement is also verified for an open-ended coaxial line. A 11 times improvement is achieved for a similar detection practice, with a λ/20 sized crack. The effect of coaxial line size and the dielectric material on the sensitivity enhancement are studied. The improvement is studied theoretically and numerically for an electrically small dipole. Theoretical studies show that when a small dipole is placed within a spherical shell made of DNG materials, the antenna parameters of the dipole becomes more sensitive to the position of a target placed outside the negative material shell. The field distribution generated by a small dipole in a multilayered spherical medium is studied for this purpose. Numerical analysis of a small dipole placed next to a planar DNG layer is presented. The DNG layer increases the sensitivity of the dipole due to a λ/30 sized metallic target by 5.5 times. To provide experimental verification, the sensitivity of an electrically small loop is studied. SNG materials with a negative permeability around 1.25 GHz are designed using modified split ring resonators (MSRR). By using the effective parameters of the designed structure, a sensitivity improvement of 10 times is achieved numerically. The improvement is verified using fabricated MSRR structures. The sensitivity of the small loop is enhanced by 9 times for a λ/12.2 sized metallic target. The sensitivity improvements are achieved within the frequency band where the MSRR structures behave as a μ-negative SNG material.

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Harrison, Richard K. 1982. „Mechanisms and applications of near-field and far-field enhancement using plasmonic nanoparticles“. Thesis, 2012. http://hdl.handle.net/2152/19462.

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The resonant interaction of light with metal nanoparticles can result in extraordinary optical effects in both the near and far fields. Plasmonics, the study of this interaction, has the potential to enhance performance in a wide range of applications, including sensing, photovoltaics, photocatalysis, biomedical imaging, diagnostics, and treatment. However, the mechanisms of plasmonic enhancement often remain poorly understood, limiting the design and effectiveness of plasmonics for advanced applications. This dissertation focuses on evaluating the mechanisms of plasmonic enhancement and distinguishing between near and far field effects using simulations and experimental results. Thorough characterization of metal nanoparticle colloids shows that electromagnetic simulations can be used to accurately predict the optical response of nanoparticles only if the true shapes and size distributions are taken into account. By coupling these optical interaction calculations with heat transfer models, experimental limits for the maximum optical power before nanoparticle melting can be found. These limits are important for plasmonic multiphoton luminescence imaging applications. Subsequently, we demonstrate ultrafast laser plasmonic nanoablation of silicon substrates using gold nanorods to identify the near-field enhancement and mechanism of plasmon-assisted ablation. The experimentally observed shape of the ablation region and reduction of the ablation threshold are compared with simulations to show the importance of the enhanced electromagnetic fields in near-field nanoablation with plasmonic nanoparticles. The targeted use of plasmonic nanoparticles requires narrow size distribution colloids, because wide size distributions result in a blurring and weakening of the optical response. A new synthesis method is presented for the seeded-growth of nearly monodisperse metal nanoparticles ranging from 10 to 100 nm in diameter, both with and without dielectric shells of controlled thickness. This method is used to acquire fine control over the position and width of the plasmonic peak response. We also demonstrate self-assembled sub-monolayers of these particles with controllable concentrations, which is ideal for looking at plasmonic effects in surface and layered geometries. Finally, we present results for the spatial distribution of absorption around plasmonic nanoparticles. We introduce field-based definitions for distinguishing near-field and far-field regions and develop a new set of equations to determine the point-by-point enhanced absorption in a medium around a plasmonic nanoparticle. This set of equations is used to study plasmon-enhanced optical absorption for thin-film photovoltaic cells. Plasmonic nanoparticle systems are identified using simulations and proof-of-concept experiments are used to demonstrate the potential of this approach.

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Duarte, Maria Inês Caramelo. „A novel plasmonic nanostructure for localized near-field light enhancement“. Master's thesis, 2019. http://hdl.handle.net/10362/94398.

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The combination of plasmonic structures with dielectric materials, metallic oxides and in particular, with two dimensional (2D) materials has been a subject of great interest in the scientific community for a wide range of applications, such as optoelectronic devices, solar cells, or photochemistry. Plasmonic properties have the potential to enhance the capabilities of 2D materials for harvesting light, which alone have a low efficiency due to low absorption (approximately only 11%). This work presents a new plasmonic structure, “nanohippo” with a perspective to integrate a monolayer material inside the cavity, being this nanostructure directly excited by the incident light taking advantage of localized surface plasmonic resonance (LSPR). The samples were prepared by colloidal lithography and material deposition was made through an electron beam assisted evaporation system. A fabrication method was developed to create a cavity by using a sacrificial material and etching it later on. The sample’s characterization consisted in a morphologic analysis by Scanning Electron Microscopy (SEM), the optical response was studied both theoretically and experimentally by Finite-difference-time-domain (FDTD) as well as experimentally by spectrophotometry. Finally, an elemental analysis was performed via X-ray photoelectron microscopy (XPS). The diameter and height of the structures were studied (different sizes nanoparticles and thicker layers of bottom layer gold) reaching to a structure that presented a plasmonic cavity. This nanostructure, with a new geometry, presented a visible plasmonic nanocavity with up to sixty times more enhancement of the electrical field inside it.

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Wong, Rong-Tsann, und 翁榮燦. „Planar Near Field to Far Field Transformation Using Equivalent Magnetic Current Approach“. Thesis, 2000. http://ndltd.ncl.edu.tw/handle/94758142368369998262.

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碩士
國立交通大學
電信工程系
88
n this thesis, we discuss the planar near field to far field transformation using equivalent magnetic current approach. Utilizing equivalence principle and image theory to replace antenna with equivalent magnetic currents, the equivalent magnetic current plane has to encompass the antenna under test. The equivalent magnetic currents are used to determine far field pattern. Under certain approximations, the equivalent magnetic current approach can produce correct far field pattern regardless of the shape of the antenna under test. From proper derivations, an electric field integral equation contains equivalent magnetic currents is developed. The equivalent magnetic currents obtained by method of moments and conjugate gradient method determine the far field pattern. Furthermore, utilizing the special structure of block Toeplitz matrix, two-dimensional fast Fourier transform is used to accelerate the conjugate gradient method and drastically reduces the computation time and storage requirements. Finally, far field patterns of the infinitesimal short dipole arrays and random infinitesimal short dipole sources are compared with analytic far field patterns to prove the equivalent magnetic current approach works fine in near field to far field transformation.

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Liu, Jun-Cheng, und 劉俊呈. „Design and Realization of Near Field Antennas for Magnetic Resonance and Magnetic Induction“. Thesis, 2017. http://ndltd.ncl.edu.tw/handle/7u6cet.

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碩士
國立高雄應用科技大學
光電與通訊工程研究所
105
The design and analysis of magnetic resonance and magnetic induction antennas are presented. Two winding coils are proposed for the magnetic resonance antenna with operating frequency of 6.78 MHz and for the frequency band at 13.56 MHz. The electromagnetic simulation software HFSS is used to optimize the design process. The fakerated coils are measured (S-parameters, transmission coefficiency) to compane with the simulation results. The magnetic resonance antennas with gradient space and equidistance space are analyzed. The gradient space antenna has hetter energy transmission than that of equidistance space. All antennas are etched on the FR4 substrates, which are net subject to deformation, reduce the size and reduce the measurement error. The magnetic induction antenna structure is also designed with a gradient spacing design. After completing the conjugate watch with the chip cards (Mifare1 S50), the RFID-EVAL-LABK near-field reading development kit is used to measure the reading distance. Take into account the environment, the displacement of the induction coil will affect the performance pro and con.

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Chen, Yan-chi, und 陳彥志. „Stray field magnetic resonance imaging：system construction, sensitivity enhancement and applications“. Thesis, 2004. http://ndltd.ncl.edu.tw/handle/50087612414809411728.

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41

Wu, Chia-Chu, und 吳家駒. „Electro-Magnetic Analysis of Near Field Wireless Power Transfer Modules“. Thesis, 2014. http://ndltd.ncl.edu.tw/handle/8k4ztw.

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碩士
國立臺北科技大學
冷凍空調工程系所
102
Since mobile phones, electric vehicles and related applications vigorously emerge, wireless charging become an attractive technology for more convenient usage.Therefore, wireless power transmission league and protocol also appeared to promote this technology. The two main league are known as Wireless Power Consortium (WLC) and Alliance for Wireless Power (A4WP). The research of this article used the wireless power transmission module which developed by the ferrite vendor. We designed for inductors for differentleagues, combo inductors for Near Field Communication (NFC) and Wireless Power Consortium (WLC) in order to compare thesimulated and measured results. At first, we confirmed the accuracy of the simulation by comparing simulated data with experimental data and then built a simulation design guide.Secondly, due to the restriction of inductor configuration and matching circuit of each league, the quality factor of inductors becomes the primary issue of this technique. To solve the problem, we added ferrite materials as the substrate of the inductor and changed the structure of the substrate. Reducing proximity effects of the inductor occur in high frequency could lead to the decrease of resistance and increase the inductance value as well as the quality factor. The charging efficiency could also be improved. The errors between measurement and the simulation were under 5%; in other words, the inductor design can be optimized in the simulation environment instead of the time-consuming methodology by trial-and-error; hence, the manufacturing costs decreased. In this study, A4WP inductor was simulated through one-to-one characteristics. Based on the results, we expected to develop one-to-many in the near future.

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Shen, Tzu-Wei, und 沈資偉. „Research on Hall sensors applied to Near-field Magnetic Induction Communication“. Thesis, 2014. http://ndltd.ncl.edu.tw/handle/31314742070281604596.

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碩士
國立交通大學
電子工程學系電子研究所
103
There is a recent trend of Internet of Things (IOT) in modern wireless communications. Due to the various applications in IOT, there are many challenges, too. (e.g., low power consumption, high data rates, and the small volume). Because many applications of IOT are used in short-distance wireless communication. Thus, choosing a suitable wireless communication method in short distance is very important. For instance, Radio-Frequency identification (RFID) is suitable for air medium, and Near Field Magnetic Induction Communication (NFMIC) is suitable for non-air media. In Comparison with RFID, unique characteristics of NFMIC particularly make it more suitable than RFID in some circumstance, where the communication environment consists of humidity, soil or body organs. In NFMIC system, coils are usually needed to generate the magnetic field to transmit signals. According to the property of coil, if we want to produce a bigger magnetic field, the coil needs more turns. In this way, the volume of coil will increase, and it is not desirable. Hall sensors have smaller volume than coils, and it can replace coils in the receiver to reduce the volume of receiver. The working principle of Hall sensors is generating voltage by Hall Effect to sense the changes of magnetic fields. However, there is a tradeoff between performance and volume. In this study, the costs of small volume consist of low capacity, short available transmission distance and bad signal to noise ratio…etc. . This paper is organized as follows. Chapter 1 introduces the Internet of things (IOT), near field magnetic induction communication (NFMIC) and Hall sensors. Chapter 2 proposes two system models; the near field magnetic induction communication system and Hall sensor based system. Chapter 3 lays out system requirements and specifications, and presents how the experiment is conducted. Then Chapter 4 compares experimental and theoretical results. Furthermore, we also compare the signal to noise ratio, and channel capacities. In the end, we summarize this thesis and propose future work directions and possible applications in Chapter 5.

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Mendes, Manuel João de Moura Dias. „Near-field nanophotonic structures for localized light enhancement in intermediate band solar cells“. Doctoral thesis, 2012. http://hdl.handle.net/10362/48651.

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Tese arquivada ao abrigo da Portaria nº 227/2017 de 25 julho.
This doctoral thesis explores some of the possibilities that near-field optics can bring to photovoltaics, and in particular to quantum-dot intermediate band solar cells (QD-IBSCs). Our main focus is the analytical optimization of the electric field distribution produced in the vicinity of single scattering particles, in order to produce the highest possible absorption enhancement in the photovoltaic medium in their surroundings. Near-field scattering structures have also been fabricated in laboratory, allowing the application of the previously studied theoretical concepts to real devices. We start by looking into the electrostatic scattering regime, which is only applicable to sub-wavelength sized particles. In this regime it was found that metallic nano-spheroids can produce absorption enhancements of about two orders of magnitude on the material in their vicinity, due to their strong plasmonic resonance. The frequency of such resonance can be tuned with the shape of the particles, allowing us to match it with the optimal transition energies of the intermediate band material. Since these metallic nanoparticles (MNPs) are to be inserted inside the cell photovoltaic medium, they should be coated by a thin insulating layer to prevent electron-hole recombination at their surface. This analysis is then generalized, using an analytical separation-of-variables method implemented in Mathematica7.0, to compute scattering by spheroids of any size and material. This code allowed the study of the scattering properties of wavelengthsized particles (mesoscopic regime), and it was verified that in this regime dielectric spheroids perform better than metallic. The light intensity scattered from such dielectric spheroids can have more than two orders of magnitude than the incident intensity, and the focal region in front of the particle can be shaped in several ways by changing the particle geometry and/or material. Experimental work was also performed in this PhD to implement in practice the concepts studied in the analysis of sub-wavelength MNPs. A wet-coating method was developed to self-assemble regular arrays of colloidal MNPs on the surface of several materials, such as silicon wafers, amorphous silicon films, gallium arsenide and glass. A series of thermal and chemical tests have been performed showing what treatments the nanoparticles can withstand for their embedment in a photovoltaic medium. MNPs arrays are then inserted in an amorphous silicon medium to study the effect of their plasmonic near-field enhancement on the absorption spectrum of the material. The self-assembled arrays of MNPs constructed in these experiments inspired a new strategy for fabricating IBSCs using colloidal quantum dots (CQDs). Such CQDs can be deposited in self-assembled monolayers, using procedures similar to those developed for the patterning of colloidal MNPs. The use of CQDs to form the intermediate band presents several important practical and physical advantages relative to the conventional dots epitaxially grown by the Stranski-Krastanov method. Besides, this provides a fast and inexpensive method for patterning binary arrays of QDs and MNPs, envisioned in the theoretical part of this thesis, in which the MNPs act as antennas focusing the light in the QDs and therefore boosting their absorption.

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Liu, Chen-Hao, und 劉辰浩. „Study on high sensitivity surface plasmon resonance sensor by magnetic field enhancement“. Thesis, 2010. http://ndltd.ncl.edu.tw/handle/56523224064934127201.

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碩士
國立東華大學
電機工程學系
98
Surface plasmon resonance sensor has been widely used in various fields by measuring the refractive index of sample. However, for the demanding of upgrade, high sensitivity and high resolution capability of the sensor are required recently. We here propose a methodology that construct a magnetic field on the surface plasmon resonance sensor to enhance the sensitivity that presented by the phase interrogation. In the thesis , we created a set of two coils to generate magnetic field, which placed on the both ends of the metal film, such that the magnetic field passed across the metal film in parallel. In the experiment, we changed the magnitude of magnetic field strength and the angle of incidence on the metal film to active plasmon resonance. He-Ne Laser with wavelength 632.8nm was chosen as the light source which passed through the desired optical path and then projected on the prism coupler where sample and magnetic field exist. Samples were alcohol solution with different concentration. The reflected beam signal was sample concentration dependent from the metal surface and was collected by optical sensor which transformed the signal to phase by a following connected lock-in amplifier. Results show that phase increases while magnetic field increasing. The optimal resolution can reach 9.68 × 10-6 RIU when the applied magnetic field was 105 Gauss and perpendicular to the metal film. Compared with the sensor without applied magnetic field, we can enhance the resonance up to 169.6%, and then demonstrate the possibility.

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Yang, Bo-kai, und 楊博凱. „An Orthogonal-direction Near-field Magnetic Probe Based on Folded-loop Structure“. Thesis, 2011. http://ndltd.ncl.edu.tw/handle/39677181935785229714.

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碩士
國立臺灣大學
電信工程學研究所
99
Near-field magnetic probes are often used to measure the magnetic fields above a printed circuit board in order to identify the sources and coupling paths of an electromagnetic interference (EMI) or radio frequency interference (RFI) problem. This thesis introduced a magnetic probe structure using two folding loop to measurement magnetic fields in two orthogonal direction. This orthogonal-direction magnetic probe using differential-mode signal and common-mode signal to distinguish orthogonal magnetic fields, has better sensitivity and E-field coupling suppression than traditional orthogonal magnetic probe. The effects of this probe are analyzed using full-wave simulations and measurements.

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Su, Bo-He, und 蘇柏合. „Probing Magnetic Field Structure in Turbulent Clouds by Near Infrared Polarization Observations“. Thesis, 2013. http://ndltd.ncl.edu.tw/handle/7vas84.

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碩士
國立中央大學
天文研究所
101
The Carina Nebula (NGC3372) and RCW 57A (NGC3576) are among the brightest Galactic nebulae, with a wealth of massive stars and infrared excess stars, suggestive of recent and ongoing star formation. We present near-infrared JHKs polarization images taken by SIRPOL, an infrared imaging polarimeter, mounted on the Infra-Red Survey Facility telescope in Sutherland, South Africa, to diagnose the magnetic field structure in these turbulent cloud complexes. Our SIRPOL field covers only the central part of Carina Nebula around Eta Carina where a cavity has been created, for which only moderate polarization is measured, mainly by the general Galactic magnetic field. In contrast, RCW 57A is associated with copious molecular clouds, and we were able to infer the hourglass shaped magnetic field that governs the cloud morphology.

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Hsu, Meng-Tse, und 徐孟澤. „A Micromaching Sub-THz Reflector Antenna for Gain Enhancement and Near Field Focus Application“. Thesis, 2018. http://ndltd.ncl.edu.tw/handle/7su4k2.

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碩士
國立交通大學
電子研究所
106
This paper will present the first silicon-based parabolic Sub-THz reflector antenna with corresponding fabrication processes. The antenna is side fed with an on-chip 340 GHz patch antenna on a reflector made of stacked micromachined silicon substrates with a parabolic-shaped Kapton film coated with aluminum on top. The antenna with a size of 18 x18 x4 mm3 and an aperture of ~10mm can be easily integrated with MMIC (Monolithic Microwave Integrated Circuit) sources, i.e. 40 nm CMOS triple-push oscillator in this case, and exhibit not only ~12.4 dB directive gain enhancement and 4.34° HPBW (Half Power BeamWidth) for far field radiation but also an excellent near field focus characteristic with a 28.5 mm depth of field (DOF). In comparison with the prior arts listed, the characteristics of small form factor, high gain enhancement and minimal HPBW has shown the potential of the reflector antenna for high-speed data transmission and THz imaging system applications.

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Fan, Jih-Hua, und 范日華. „Study of Near-Field Plasmonic Enhancement of the Golden Nanoparticles Embedded in Ga2O3 Shell“. Thesis, 2010. http://ndltd.ncl.edu.tw/handle/35620314167055929285.

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碩士
國立交通大學
光電工程學系
98
We study near-field plasmonic enhancement of the golden nanoparticles embedded in Ga2O3 shell by using finite difference time domain method (FDTD) and near-field scanning probe microscopes. In two-dimensional FDTD simulation, we explore the variations of field distributions with different sizes and shapes of metallic particles, gap distances between particles and the width of the Ga2O3 shell. We observe that plasmonic gap enhancement increases with either the decrease of gap distances or the increase of particles’ sizes. In addition, near-field gap-enhanced factor for the structure embedded in the Ga2O3 shell is larger than that embedded in the air due to higher refractive index of Ga2O3. We use three-dimensional FDTD method to obtain the field distributions of the whole structure with different incident wavelengths. Gap enhancement is reduced as the field propagates through the Ga2O3 shell due to diffraction. Besides, higher field intensity and enhancement are observed at the interface of Ga2O3 and the air as the incident wavelength is near to the resonant wavelength of the structure. In experiments, we use the scanning probe microscopes and near-field optical microscopes to obtain the structure parameters and near-field optical images of the sample. Observing images obtained by the atomic force microscope and the electrostatic force microscope, we acquired the diameters of golden nanoparticles are from 20nm to 90nm, the gap distances are from 20nm to 100nm and the shellwidths are from 100nm to 300nm. Images seen in near-field scanning optical microscope with different launched light sources show higher field intensity and enhancement are observed as the light source is green, showing the structure is wavelength selective. Additionally, the resonant wavelength of this structure is at the regime of 520–570 nm based on the results obtained by 3D simulations.

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Bitzer, Andreas [Verfasser]. „Terahertz near-field imaging of electric and magnetic resonances / vorgelegt von Andreas Bitzer“. 2009. http://d-nb.info/1000549690/34.

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Huang, Ru-Yu, und 黃如玉. „A Power Supply of Rectified System for Reverse Current Self-calibration through Magnetic Field Induction in Near Field Communication“. Thesis, 2015. http://ndltd.ncl.edu.tw/handle/4yck4j.

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Annotation:

碩士
國立交通大學
電機工程學系
104
As the growing of sensing technique, near field communication (NFC) becomes an essential part in the mobile devices in the near future. NFC devices can be operated at the condition of low battery or even battery-off due to the requirement of payment any time. Power by field can supply the controller of NFC devices continuous and stable voltage source to ensure the act of tag in card emulation (CE) mode operates smoothly. As a result, it is crucial in NFC controllers for power source transferred from mutual induction of coils when the devices are battery-off. The proposed technique of power source designed in 0.25 μm CMOS process was used to rectify AC source from induction of magnetic field to unregulated DC voltage source and to supply power the NFC controller through low dropout regulator (LDR). Moreover, the developed rectified systems achieve as high as 92% voltage conversion ratio and 89.4 % power conversion efficiency (PCE) due to the reduction of unnecessary current loss.

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Dissertationen zum Thema „Near field magnetic enhancement“

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