In this paper a psychoacoustic sound field synthesis (pSFS) system for musical applications is presented. It recreates the radiation patterns of musical instruments for an extended listening area. For this purpose several psychoacoustic effects are utilized: Considering the critical bandwidth, the amount of data to be processed can be reduced massively. Applying a “precedence fade” allows for wave fronts to arrive from angles opposing to the virtual source position when regarding the integration time of the auditory system and phenomenons known from the field of auditory scene analysis. A listening test demonstrates that the approach results in a precise source localization together with a spatial sound impression which is known to be the most crucial aspect of the subjective acoustical quality of concert halls. This is achieved even in a reverberant room and with a relatively large distance between loudspeakers compared to other wave field synthesis systems. Implementations in audio systems such as 5.1 or wave field synthesis systems with a large number of loudspeakers are possible.

Modélisation du couplage mutuel présent dans un réseau d'antennes : étude théorique, applications au radar MIMO et à un contexte RFID. Le couplage mutuel est un phénomène électromagnétique susceptible de se produire dans les réseaux d'antennes. Il est dû aux interactions électromagnétiques qui se produisent entre les éléments d'un réseau d'antennes et induisent une modification des paramètres intrinsèques des antennes. Lorsque la distance inter-élément diminue, les effets du couplage mutuel augmentent. La prise en compte du couplage mutuel dans les réseaux d'antennes, lors de leur conception ou dans les algorithmes de traitement d'antennes, permet d'avoir accès aux caractéristiques de rayonnement réel de chaque élément du réseau, ce qui peut par exemple permettre d'améliorer les performances de détection/localisation de cibles à l'aide d'un radar MIMO (Multiple Input Multiple Output). Dans un contexte RFID (Radio Frequency IDentification), modéliser le couplage mutuel permet de modéliser le système formé par un ensemble de tags et de statuer sur le comportement du système dans une configuration donnée. Cette thèse porte sur la modélisation du couplage mutuel présent dans un réseau d'antennes. Nous avons d'abord proposé une nouvelle méthode de modélisation du diagramme de rayonnement de l'élément actif basée sur la résolution de problèmes d'optimisation au sens des moindres carrés pour trouver les pondérations complexes qui modélisent les interactions électromagnétiques entre les éléments du réseau. Ces pondérations complexes peuvent être utilisées comme des lois d'excitation à appliquer à une antenne isolée décrivant les positions des éléments du réseau, afin d'étudier expérimentalement le comportement d'un réseau d'antennes. Cette modélisation du couplage mutuel est ensuite appliquée dans un contexte radar MIMO où nous montrons qu'il est possible de synthétiser le diagramme de rayonnement de l'élément actif sur une plateforme expérimentale de radar MIMO composée d'une seule antenne émettrice et d'une seule antenne réceptrice qui se déplacent sur des rails en des positions prédéfinies. A la réception, la matrice des signaux reçus est obtenue en appliquant le principe de superposition. Nous avons également cherché à modéliser le couplage mutuel en proposant une formulation théorique de l'impédance mutuelle entre les éléments d'un réseau de dipôles fins aléatoirement répartis dans un plan afin d'appliquer cette modélisation du couplage mutuel à un contexte RFID, où les tags, représentés par les dipôles, sont éparpillés dans un plan et éclairés par un lecteur. Nous avons également proposé une formulation théorique de l'impédance d'entrée du dipôle environné et avons étudié les effets du couplage mutuel sur les deux paramètres intervenant dans le bilan d'une liaison RFID : l'adaptation (la bande passante) et le diagramme de rayonnement du dipôle environné. Nous avons montré qu'il était possible de synthétiser le diagramme de rayonnement du dipôle environné et de trouver la modification de l'adaptation du dipôle environné, ce qui, à terme, permettrait de statuer sur le taux et/ou la distance de lecture d'une communication RFID dans un contexte haute densité / Modeling of the Mutual Coupling Present in an Antenna Array: TheoreticalStudy, Applications to MIMO Radar and RFID ContextMutual coupling is an electromagnetic phenomenon that can occur in antenna arrays. It is due to the electromagnetic interactions that occur between the elements of an antenna array and induce a modification of the intrinsic parameters of the antennas. Taking into account mutual coupling in antenna arrays, when designing them or in antenna processing algorithms, provides access to the real radiation characteristics of each array element which can, for example, improve target detection/localization performance using a Multiple Input Multiple Output (MIMO) radar. In an RFID (Radio Frequency IDentification) context, modeling mutual coupling makes it possible to model the system formed by a set of tags and to decide on the behavior of the system in a given configuration. This thesis focuses on the modeling of the mutual coupling present in an antenna array. We first new method for the active element pattern synthesis based on solving optimization problems in the least squares sense to find the complex weights that model electromagnetic interactions between network elements. These complex weights can be used as excitation laws to be applied to an isolated antenna describing the positions of the array elements, in order to experimentally study the behavior of an array of antennas. This mutual coupling modeling is then applied in a MIMO radar context where we show that it is possible to synthesize the radiation pattern of the active element on an experimental MIMO radar platform composed of a single transmitting and a single receiving antenna that moves on rails in predefined positions. On reception, the matrix of received signals is obtained by applying the principle of superposition. We also sought to model mutual coupling by proposing a theoretical formulation of the mutual impedance between the elements of an array of fine dipoles randomly distributed in a plane in order to apply this mutual coupling modeling to an RFID context, where the tags, represented by the dipoles, are scattered in a plane and illuminated by a reader. We also proposed a theoretical formulation of the input impedance of the surrounding dipole and studied the effects of mutual coupling on the two parameters involved in the balance of an RFID link: the adaptation (bandwidth) and the radiation pattern of the surrounding dipole. We have shown that it is possible to synthesize the radiation pattern of the surrounded dipole and to find the modification of the adaptation of the surrounded dipole, which, in the long term, would allow to decide on the read rate and/or the reading distance of an RFID communication in a high density context.

High-frequency signal far-field measurement systems usually involve the use of complex and expensive equipment, since the measurements must be made at a distance of multiple wavelengths from the antenna. Helicopter surveyors are commonly utilized. However, in recent years, much research has focused on ways to lower measurement costs by lowering flying expenses or equipment costs, for as using helium aerostats. Despite this, costs are still high. The research question is whether the measurement of the far-field properties of HF-antennas can be accomplished using a simple low-cost GPS-configured unmanned aerial vehicle (UAV) and a simple single-frequency transmitter. The study includes the design and experimental verification of a radiation pattern measurement system for HF antennas, for which measurement accuracy is discussed. Finally, limitations and implementation-related issues are discussed. / System för mätning av högfrekventa signalers fjärrfält kräver vanligtvis komplicerad och dyr utrustning, eftersom mätningarna måste göras på ett avstånd av flera våglängder från antennen. Helikopterundersökningar används vanligtvis, men på senare år har mycket forskning fokuserat på att sänka mätningskostnaderna genom att sänka flygkostnaderna eller utrustningskostnaderna, exempelvis genom att använda heliumaerostater. Trots detta är kostnaderna fortfarande höga. Forskningsfrågan är om mätning av högfrekventa signaler kan utföras med hjälp av en enkel och billig obemannade flygplan (UAV) konfigurerade med GPS och en enkel enskild frekvenssändare. Studien omfattar konstruktion och experimentall verifiering av ett system för uppmätning av strålningsdiagram för HF-antenner, där mätnoggrannheten diskuteras. Slutligen diskuteras begränsningar och implementeringsrelaterade frågor.

This thesis describes development of a miniature reconfigurable antenna and optimization of a dual tuned birdcage coil. The design goals for the miniature reconfigurable antennas are resonance center frequency of 2.44 GHz, bandwidth of 2.4 GHz - 2.48 GHz, size of 0.8 cm x 1.2 cm, radiation efficiency of 70%, pattern correlation coefficient of 0.3 and input impedance of 50 Ω. The main goals to be achieved from the birdcage coil are the better homogeneity and higher signal to noise ratio than the existing coil. The design and optimization of both antenna and birdcage coil were done using simulation software and MATLAB. Wireless communications have progressed rapidly in last decade and communication devices are becoming smaller and smaller. With miniaturization of devices, dimensions of antennas need to be reduced accordingly. In recent years engineers have not only focused on miniaturization but also on the reconfigurability of the antenna. The functionality and performance of an antenna can be greatly improved by a reconfigurable antenna. However, designing such an antenna can be a tricky task. This thesis addresses issues that are faced during design of such miniature reconfigurable antenna. It also describes design and optimization of such an antenna. The modeled and measured results for the miniature reconfigurable antennas were very close except the built antenna requires frequency tuning and better switching technique. Magnetic resonance imaging (MRI) is an imaging modality that provides high quality images. Radio frequency (RF) coils play an important role in MRI. RF coils act like an antenna that transmits RF energy and receives energy as well. The most commonly-used RF coil for volume imaging is the birdcage coil. This thesis describes an optimization of a birdcage coil that is dual tuned for sodium and hydrogen frequencies. The modeled coil has better performance compared to the existing coil.

La radiogoniométrie joue un rôle crucial dans diverses applications, aussi bien civiles que militaires, liées soit à la radionavigation ou à la radiolocalisation. La plupart des antennes de goniométrie opèrent sur une large bande de fréquences, mais seule une minorité d’entre elles permettent l'estimation de la direction d’arrivée d’un champ électromagnétique incident sur une couverture angulaire 3-D (c.-à-d., l’estimation à la fois des angles d’azimut et d’élévation). Une approche originale permettant d’obtenir une couverture angulaire 3-D consiste à mesurer les six composantes d’un champ électromagnétique incident à l’aide d’une antenne dite vectorielle. L'objectif de cette thèse est de concevoir une antenne vectorielle passive, compacte et large bande afin de couvrir un maximum d'applications. Deux antennes vectorielles ont été conçues, fabriquées et caractérisées expérimentalement. \`A la différence d'une topologie conventionnelle, elles permettent de mesurer les composantes d'un champ électromagnétique incident grâce à la reconfigurabilité en diagramme de rayonnement d'un arrangement original d'antennes Vivaldi. Le premier prototype est monté sur un support métallique fini et permet l'estimation de la direction d'arrivée de champs électromagnétiques polarisés verticalement sur une bande passante de 1.69:1 tandis que le second peut être utilisé quelle que soit la polarisation des champs électromagnétiques incidents sur une bande passante de 8:1. De plus, les performances de goniométrie de ces antennes vectorielles ont été améliorées du point de vue de la précision, de la sensibilité, de la robustesse face aux ambiguïtés angulaires et aux erreurs de dépolarisation en synthétisant de nouveaux diagrammes de rayonnement dans le processus d'estimation. Une méthode basée sur la borne de Cramer-Rao a été élaborée afin de sélectionner efficacement et rapidement les diagrammes de rayonnement supplémentaires. / Direction finding plays a crucial role in various civilian and military applications, related to either radionavigation or radiolocation. Most of the direction finding antennas operate over a wide frequency band, but only a minority of them enable the direction of arrival estimation of an incoming electromagnetic field over a 3-D angular coverage (i.e., estimation of both azimuth and elevation angles). An original approach to obtain a 3-D angular coverage consists in measuring the six components of the incident electromagnetic field through a so-called vector antenna. The aim of this Ph.D. is to design a passive, compact and wideband vector antenna in order to cover a maximum of applications. Two vector antennas have been designed, manufactured and experimentally characterized. Unlike conventional topology, they enable the measurement of the components of an incoming electromagnetic field thanks to the radiation pattern reconfigurability of an original arrangement of Vivaldi antennas. The first prototype is mounted over a finite metallic support and enables the direction of arrival estimation of vertically-polarized electromagnetic fields over a 1.69:1 bandwidth while the second one can be used regardless of the polarization of the incoming electromagnetic fields over a 8:1 bandwidth. Moreover, the direction finding performances of these vector antennas have been improved in terms of estimation accuracy, sensitivity, robustness to angular ambiguity and polarization mismatch by synthesizing new radiation patterns in the estimation process. A method based on the Cramer-Rao lower bound has been proposed to select efficiently and rapidly the additional radiation patterns

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Utilising future radio interferometer arrays, such as the Square Kilometre Array (SKA), to their full potential will require calibrating for various direction- dependent effects, including the radiation pattern (or primary beam in the parlance of radio astronomers) of each of the antennas in such an array. This requires an accurate characterisation of the radiation patterns at the time of observation, as changing operating conditions may cause substantial variation in these patterns. Furthermore, fundamental imaging limits, as well as practical time constraints, limit the amount of measurement data that can be used to perform such characterisation. Herein three techniques are presented which aim to address this requirement by providing pattern models that use the least amount of measurement data for an accurate characterisation of the radiation pattern. These methods are demonstrated through application to the MeerKAT Offset Gregorian (OG) dual-reflector antenna. The first technique is based on a novel application of the Jaco bi-Bessel series in which the expansion coefficients are solved directly from the secondary pattern. Improving the efficiency of this model in the desired application leads to the development of a different set of basis functions, as well as two constrained solution approaches which reduce the number of pattern measurements required to yield an accurate and unique solution. The second approach extends the application of the recently proposed Characteristic Basis Function Patterns (CBFPs) to compensate for non-linear pattern variations resulting from mechanical deformations in a reflector antenna system. The superior modelling capabilities of these numerical basis functions, which contain most of the pattern features of the given antenna design in a single term, over that of analytic basis functions are demonstrated. The final method focusses on an antenna employing a Phased Array Feed (PAF) in which multiple beam patterns are created through th e use of a beam-former. Calibration of such systems poses a difficult problem as the radiation pattern shape is susceptible to gain variations. Here we propose a solution which is based on using a Linearly Constrained Minimum Varia nce (LCMV) beamformer to conform the realised beam pattern to a physics-based analytic function. Results show that the LCMV beamformer successful ly produces circularly symmetric beams that are accurately characterised with a single-term analytic function over a wide FoV. / AFRIKAANSE OPSOMMING: Die volle benutting van toekomstige radio interferometersamestellings, soos die Square Kilometre Array (SKA), benodig die kalibrering van verskeie rigting-afhanklike effekte, insluitend die stralingspatroon (bekend as die primêre bundel onder radio astronome) van elke antenne in só ’n samestelling. Hierdie benodig ’n akkurate karakterisering van die stralingspatrone op die waarnemingstydstip, aangesien veranderende bedryfskarakteristieke ’n beduidende afwyking in hierdie patrone veroorsaak. Verder, weens fund amentele perke in beeldverwerking, asook praktiese tydbeperkinge, bestaan daar ’n limiet op die hoeveelheid gemeetde data wat benut kan word om die nodige karakterisering mee te doen. Hierin word drie tegnieke ten toon gestel wat gemik is daarop om aan hierdie behoefte te voorsien deur die gebruik van modelle wat ’n minimum hoeveelheid metingdata benodig om ’n akkurate beskrywing van die stralingspatroon te lewer. Die verskeie metodes word aangebied aan die hand van die MeerKAT afset-Gregorian dubbelreflektorantenne. Die eerste tegniek is gebasseer op ’n nuwe toepassing van die Jacobi- Besselreeks waarin die sekondêre stralingspatroon direk gebruik word om die uitsettingskoëffisiënte op te los. Die doelmatigheidsverbetering van hierdie model in die huidige toepassing lei na die ontwikkeling van ’n nuwe versameling van basisfunksies, asook twee voorwaardelike oplossings wat die nodige aantal metings vir ’n akkurate, unieke oplossing verminder. In die tweede tegniek word die toepassing van die onlangs voorgestelde Karakteristieke Basisfunksie Patrone uitgebrei om te vergoed vir die nie-lineêre stralingspatroonafwykings wat teweeggebring word deur meganiese vervormings in die reflektorantenne. Die superieure modelleringsvermoëns van hierdie numeriese basisfunksies, wat meeste van die patroonkenmerke vasvang in ’n enkele term, bo dié van analitiese basisfunksies word gedemonstreer. Die laaste metode fokus op die gebruik van ’n gefaseerde samestellingvoer waarin veelvoudige bundelpatrone geskep word deur die gebruik van ’n bundelvormer. Die kalibrering van sulke instrumente word bemoeilik daardeur dat die patroonvorm gevoelig is vir aanwinsafwykings. Hier stel ons ’n oplossing voor waarin ’n lineêrbegrensde minimumstrooiing bundelvormer gebruik word om die stralingspatroon te pas op ’n fisika-gebasseerde analitiese funksie. Resultate toon dat hierdie bundelvormer sirkelsimmetriese bundels kan skep wat akkuraat beskryf word deur ’n een-term analitiese funksie oor ’n wye gesigsveld.

Baigiamajame magistro darbe, analitinėje dalyje, pateikta žinomi radiolokatorių antenų elektromagnetinio spinduliavimo kryptinių diagramų matavimo būdai bei svarbiausios matavimo sistemos dalies – imtuvo projektavimo teorija. Eksperimentinėje magistro darbo dalyje panagrinėti būsimi kryptinių diagramų nustatymo būdai, vienas iš jų - panaudojant elektromagnetinių bangų išsibarstymą ore. Pagal žinomus duomenis apie šį efektą sudaryta nauja alternatyvi sistema, kuri leidžia pagreitinti, sumažinti laiko bei materialines sąnaudas atliekant periodinius kryptinių diagramų matavimus ir pateiktos bendros išvados ir rekomendacijos. Darbą sudaro 7 dalys: įvadas, pagrindinės radiolokacinių sistemų techninės charakteristikos, elektroninė matavimo technika, RLS kryptinių diagramų matavimo būdai, bendros išvados ir rekomendacijos, literatūros sąrašas, priedai. / Already known Antennas Radiation Pattern Measuring Systems and theoretical Knowledge, that will help design most important part (Receiver) of measuring system, are presented In my Analysis Part of Master Work. In Experimental part there are new, that still aren’t in practical measuring used, Antennas Radiation Pattern Measuring Systems investigated. One of them is using electromagnetic Wave Scattering from Particles in the Air. Regarding all available Data’s about that effect I made System that allows us to decrease Antenna’s radiation pattern measuring time and expenses. Also made and presented some Advantages, Recommendations and Conclusions. In Master Work is 7 Parts: Introduction, Basic Radiolocation Systems technical Characteristics, Measuring Technique, Radiolocation Systems Antennas radiation patterns Measuring Methods, Conclusions, References, Supplement.

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The aim of this study is to analysis, investigate and find out the solutions for the problems associated with the implementations of antennas RFID Reader and Tag for various applications. In particular, the efficiency of the RFID reader antenna and the detection range of the RFID tag antenna, subject to a small and compact antenna's design configuration have been studied. The present work has been addressed directly to reduce the cost, size and increase the detection range and communication reliability of the RFID framework antennas. Furthermore, the modelling concept of RFID passive tags mounted on various materials including the novel design of RFID reader antenna using Genetic Algorithm (GA) are considered and discussed to maintain reliable and efficient antenna radiation performances. The main benefit of applying GA is to provide fast, accurate and reliable solutions of antenna's structure. Therefore, the GA has been successfully employed to design examples: meander-line, two linear cross elements and compact Helical- Spiral antennas. In addition, a hybrid method to model the human body interaction with RFID tag antenna operating at 900MHz has been studied. The near field distribution and the radiation pattern together with the statistical distribution of the radiation efficiency and the absorbed power in terms of cumulative distribution functions for different orientation and location of RFID's tag antenna on the human body have been demonstrated. Several tag antennas wi th symmetrical and unsymmetrical structure configurations operating in the European UHF band 850-950 MHz have been fabricated and tested. . The measured and simulated results have been found to be in a good agreement with reasonable impedance matching to the typical input impedance of an RFID integrated circuit chip and nominal power gain and radiation patterns.