Dissertations / Theses on the topic 'Beam Steering Antennas'

ITC/USA 2009 Conference Proceedings / The Forty-Fifth Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2009 / Riviera Hotel & Convention Center, Las Vegas, Nevada
New technologies are sought to meet the requirements of evolving telemetry capabilities such as new operating bands, increased test article and ground segment collaboration, and on-the-fly quality of service (QOS) management. Smart antennas may contribute to this evolution by directing signal energy where and when it is needed. Direct spatial antenna modulation (DSAM) represents a new approach to cost-effective smart antennas potentially offering benefits such as post-amplifier modulation, polarization reconfigurability, phase-shifterless phased arrays, oscillator-less frequency conversion, and pre-receiver processing gain. The basic DSAM approach has recently been proven through analysis, simulation, and prototyping, with significant implications for future capabilities.

ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California
Direct spatial antenna modulation (DSAM) is a new approach to phased array control that opens up new "smart antenna" architecture possibilities. The DSAM technique leverages the inherent spatial differences of excitation in an antenna in a novel way to achieve the equivalent of conventional modulation and beam control effects. Smart antenna techniques are of potentially increasing importance to test range operations given a trend toward more flexible, internetworked, and autonomous test activities. The DSAM technique has been demonstrated through several generations of analysis, simulation, and prototyping, but has previously only been applied to narrowband antenna designs. Furthermore, the IQ DSAM approach in particular has not been previously implemented in hardware. This paper details the application of IQ DSAM to achieve wideband phase control using a commercial off the shelf (COTS) antenna. The phase control performance of IQ DSAM over a range of 1.5 GHz to 4 GHz is measured across relative field control angles of +/- 45 degrees. The measured IQ DSAM performance is compared to what could be expected from a conventional phased array element control architecture.

In this study, the Dual Beam Phased Array Antenna System designed for COST260* project is upgraded to have the abilities of beam steering, tracking and direction finding by providing the necessary computer codes using C++ Programming Language. The functions of new prototype are tested to verify the operation. *COST260 project was an adaptive phased array receiving antenna system for satellite communication, which was operating at 11.49-11.678 GHz band.

In recent years, multi-functional reconfigurable antennas (MRA) has attracted much attention in wireless communication. The reconfigurable antenna can adapt itself with changing system conditions, and it can provide different multi-functionalities which can give better system performances. Instead of using multiple antennas, a single reconfigurable antenna can provide the same performance and occupy less space. By using the parasitic layer technique, an antenna can be turned into a reconfigurable antenna. The main objective of this thesis is to study radiation pattern reconfiguration of the horn antenna by using the parasitic layer concept. The MRA consists of a single horn, dielectric loaded truncated pyramid (DLTP), and the parasitic layer. The antenna that is chosen in this thesis is the horn antenna because it provides high directivity. DLTP is used for magnification purpose. The results show that three modes of operations that provide better performances compared to the single horn antenna are achieved.

International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California
This paper describes a flexible telemetry data link developed by National Nuclear Safety Administration’s Kansas City Plant (NNSA-KCP) and the University of Kansas (KU) in support of NNSA’s Remote Sensing Laboratory (NNSA-RSL) located at the Nevada Test Site. This data link is based on a beam steerable phased array antenna (PAA). The paper describes the PAA and the Airborne Measurement System (AMS) application requiring signal source tracking. It highlights flight test data collected during recent flight testing on the Nevada Test Site for the AMS.

The thesis is focused on the research of THz antenna arrays to be used for communications. Attention is turned to modeling metallic surfaces at THz frequencies, a proper characterization of gold conductivity, its relation to Drude model and corresponding measurements. Moreover, the best methods for modeling thin metallic layers (depending on the skin depth related to the metal thickness) are presented. An optimized element of a THz 2×2 antenna array designed for the application of communications is developed in a way that enables an expansion to a larger array. The expansion ability is demonstrated on a 4×4 antenna array which is presented in the thesis too. The designed antennas achieve parameters better than the state-of-art antennas. The presented antennas radiate circularly polarized wave at THz frequencies, operate in a wide bandwidth, have a high gain and are of a compact size. In the thesis, an 8×8 antenna array with a beam steering capability is presented. The main beam of the antenna array can be controlled in two dimensions. A high gain of the radiated circularly-polarized wave can be achieved that way. Different approaches to modeling antennas with thin metallic layers are compared and the best methods are recommended from the viewpoint of different requirements. The designed 2×2 and 4×4 antenna arrays are manufactured using a microfabrication technology. Each step of the fabrication is described in detail and discussed. The reflection coefficient at the input of antennas is measured and compared with simulations. Discrepancies in results are associated with surface roughness which is analyzed by a scanning probe microscope and a scanning electron microscope. By down-scaling the developed THz antenna, a low-profile high-gain antenna for Ka-band space applications is designed. The presented antenna achieves better results than state-of-art CubeSat antennas. The antenna performance is verified by a prototype to be operated at 9 GHz, and the radiation characteristics are experimentally confirmed.

De nos jours, les antennes à réseaux transmetteurs attirent un grand intérêt pour de nombreuses applications civiles et militaires aux bandes de fréquence comprises entre 10 et 110 GHz (réseaux de communication 5G, liens point à point, radars, etc.).Le travail de thèse vise à faire des innovations dans la modélisation et la conception d'antennes à réseaux transmetteurs pour des applications en bande Ka (28-40 GHz). Il porte plus précisément sur le développement d'outils numériques pour l’analyse théorique des réseaux transmetteurs, la conception et la démonstration de plusieurs prototypes avec des fonctionnalités avancées, telles que des réseaux transmetteurs passifs (larges bandes ou à multifaisceaux) et actifs (à reconfiguration électronique).La première partie des travaux consiste en une analyse théorique des réseaux transmetteurs. Dans un premier temps, l’impact de la méthode de compensation de phase sur les performances des réseaux transmetteurs est étudié. La loi de compensation de phase de l’onde quasi-sphérique incidente sur l’ouverture du réseau transmetteur est calculée en utilisant deux méthodes nommées compensation à phase constante et compensation par ligne à retard, et nous montrons que cette dernière permet d’augmenter la bande passante du réseau transmetteur et de corriger les erreurs de dépointage du faisceau. Dans un second temps, le principe de fonctionnement des réseaux transmetteurs facettés est décrit en détail. La simulation numérique du réseau transmetteur à trois facettes est validée au travers de simulations électromagnétiques 3-D. Pour un certain angle d’inclinaison, nous montrons que la bande passante et la capacité de dépointage du réseau transmetteur sont améliorées au détriment du gain.La suite des travaux porte sur la conception et le prototypage de deux réseaux transmetteurs passifs, dont l’un à faisceau collimaté et très large bande et l’autre à quatre faisceaux fixes. Les deux réseaux transmetteurs sont basés sur une cellule élémentaire à 3bits qui assure une double fonction à savoir la compensation de phase et la conversion de la polarisation linéaire en circulaire. Le réseau passif à faisceau collimaté présente un gain mesuré de 33,8 dBi (correspondant à une efficacité d'ouverture de 51,2%) et une bande passante à -3 dB supérieure à 15,9%. La distribution de phase du réseau transmetteur à quatre faisceaux a été optimisée par un algorithme génétique afin d’avoir des faisceaux dépointés à ± 25° dans le plan horizontal et le plan vertical à la fréquence d’optimisation.La dernière partie des travaux vise la conception d’un réseau transmetteur reconfigurable à 27-31 GHz. Dans un premier temps, une cellule élémentaire active à quatre états de phase (2 bits) en polarisation linéaire a été conçue et validée expérimentalement. Elle est composée de six couches métalliques imprimées sur trois substrats. Les éléments rayonnants sont des antennes patch rectangulaires comprenant chacun deux diodes PIN pour contrôler la phase de transmission. Le principe de fonctionnement de la cellule élémentaire a été validé expérimentalement avec des pertes d’insertion minimales de 1.6-2,1 dB et une bande passante en transmission (à 3 dB) de 10-12,1% pour les quatre états de phase 0 °, 90°, 180° et 270°. Cette cellule a ensuite été utilisée pour la conception d’un réseau transmetteur reconfigurable comprenant 14 × 14 cellules unitaires et 784 diodes PIN. Un prototype a été réalisé et caractérisé, il présente un gain maximum mesuré de 19,8 dBi, correspondant à une efficacité d'ouverture de 23,5%, et une bande passante à 3 dB de 4,7 GHz (26,2-30,9 GHz). Malgré quelques éléments défaillants, ce prototype valide le principe de fonctionnement et la faisabilité de réseaux transmetteurs en bande Ka avec une quantification de phase de 2 bits et constitue une des premières réalisations de ce type dans l’état de l’art actuel
Nowadays, transmitarray antennas are of great interest for many civil and military applications in frequency bands between 10 and 110 GHz (5G mobile networks, point-to-point communication systems, radars, etc.).This thesis aims to make major innovations in modeling and design of transmitarray antennas for Ka-band applications (28-40 GHz). It focuses on the development of numerical tools, and the design and demonstration of several prototypes with advanced functionalities, such as passive (broadband or multibeam) and active (at electronic reconfiguration) transmitarrays.The first part of the work consists of a theoretical analysis of the transmitarray antenna. In a first step, the impact of the phase compensation method on the performance of the transmitarray is studied. The phase compensation law of the quasi-spherical wave incident on the array aperture is calculated using two methods called constant phase compensation and true-time delay (TTD) compensation. The numerical results show that TTD compensation allows an increase of the transmitarrays bandwidth and a reduction of the beam squint as compared to constant phase-shift compensation. In a second step, the operating principle of facetted transmitarrays is described in detail. The numerical simulation of a 3-facet transmitarray is validated through 3-D electromagnetic simulations. For a certain facet angle, the bandwidth and the beam scanning capability of the TA are improved at the expense of the gain.The next step of the work concerns the design and prototyping of two passive transmitarray antennas, one with a collimated and a large bandwidth, and the other with four fixed beams. The two transmitarrays are based on a 3-bit unit-cell providing two functions, namely the phase compensation and the polarization conversion from linear to circular. The passive beam-collimated transmitarray exhibits a measured gain of 33.8 dBi (corresponding to an aperture efficiency of 51.2%) and a 3-dB gain-bandwidth larger than 15.9%. The quad-beam transmitarray phase distribution has been optimized by a genetic algorithm code coupled with an analytical tool. The array is designed to radiate four beams at ±25° in the horizontal and vertical planes at the optimization frequency.The last part of the work aims to the design of a 27-31 GHz reconfigurable transmitarray antenna. Initially, an active unit-cell with four phase states (2 bits) in linear polarization was designed and validated experimentally. It consists of six metal layers printed on three substrates. The radiating elements are rectangular patch antennas, each of them including two PIN diodes to control the transmission phase. The operating principle of the unit-cell has been experimentally validated with a minimum insertion loss of 1.6-2.1 dB and a 3-dB transmission bandwidth of 10-12.1% for the four phase states. 0°, 90°, 180° and 270°.Then, this unit-cell was used for the design of a reconfigurable transmitarray antenna comprising 14 × 14 unit cells and 784 PIN diodes. A prototype was realized and characterized, it presents a measured maximum gain of 19.8 dBi, corresponding to an aperture efficiency of 23.5%, and a 3-dB bandwidth of 4.7 GHz (26.2% at 30.9 GHz). Despite some faulty elements, this prototype validates the operating principle and the feasibility of Ka-band transmitarray antennas with a 2-bit phase quantization. It is one of the first demonstration of such an antenna in the current state of the art

De nombreuses applications civiles et militaires (faisceaux hertziens, futurs réseaux mobiles, communications par satellite, radars automobiles, systèmes d’imagerie haute résolution) nécessitent des antennes à faisceau reconfigurable (dépointage de faisceau, faisceaux multiples, faisceaux formés). Les antennes à réseaux transmetteurs apparaissent comme une alternative aux réseaux phasés classiques ou aux réseaux réflecteurs pour ces applications. L’objectif principal de cette thèse est de démontrer la faisabilité de réseaux reconfigurables fabriqués avec des technologies standards en bande Ka (20-30 GHz). Divers cellules élémentaires utilisant des diodes p-i-n et fonctionnant en polarisation linéaire ou circulaire ont été conçues, optimisées et caractérisées. Les mesures en guide d’onde montrent des pertes minimales de 1,09 dB à 29,0 GHz et une bande passante à 3 dB de 14,7%. Une méthode de simulation hybride a été développée afin d’analyser efficacement des réseaux de grandes dimensions utilisant des rotations séquentielles d’éléments pour optimiser la qualité de polarisation et les diagrammes de rayonnement. Un réseau de 400 cellules élémentaires fonctionnant en polarisation circulaire a été réalisé et testé en chambre anéchoïque. Un dépointage électronique de ±60° et la possibilité de commuter entre les deux polarisations circulaires (droite/gauche) ont été démontrés
Several civil and military applications (hertzian beams, satellite communications, automotive radars, high resolution imaging systems) require antennas with reconfigurable beam capabilities (beam-scanning, beamshaping, multiple beam generation). Transmitarray antennas are good candidates and represent an alternative to classical phased arrays or reflect-arrays for these applications. The main objective of this thesis is to demonstrate the feasibility of reconfigurable transmitarrays fabricated with standard technologies in Ka-band (20-30 GHz). Different unit-cell designs based on p-i-n diodes have been developed to work in linear and circular polarization. Their optimization and experimental characterization have been performed. Waveguide measurements show insertion losses of 1.09 dB at 29.0 GHz with a 3-dB bandwidth of 14.7%. A hybrid simulation technique has been developed in order to analyze efficiently large transmitarrays in which the sequential rotation technique has been applied to optimize the polarization quality and the radiation patterns. A 400-elements transmitarray operating in circular polarization has been realized and tested in anechoic chamber. A beam-scanning angular coverage of ±60° and circular polarization selection (left/right) have been demonstrated

A simple and novel dual-CP printed antenna is modelled and measured. The patch antennais small and achieves a low axial ratio without quadrature feeding. The measured pattern showsaxial ratio pattern squinting over frequency. Possible methods of improving the individual element are discussed, as well as an array technique for improving the axial ratio bandwidth. Three endfire printed antenna structures are designed, analyzed, and compared. The comparison includes an analysis of costs of production for the antenna structures in addition to their performance parameters. This analysis concludes that cost of materials primarily reduces the size of antennas for a given gain and bandwidth. An antenna stucture with an annular beam pattern for down-looking navigational radar is proposed. The antenna uses sub-wavelength grating techniques from optics to achieve a highly directive planar reflector which is used as a ground plane for a monopole. A fan-beam array element is fabricated for use in a digitally steered receive array for obstacle avoidance radar. The steered beam pattern is observed. The element-dependent phase shifts for a homodyned signal in particular are explored as to their impact on beam steering.

Millimeter-wave systems introduce a set of particular severe requirements from the antenna point of view in order to achieve specific performances. In this sense, high directive antennas are required to overcome the huge extra path loss. Moreover, each particular application introduces additional requirements. For example, in very high throughput (VHT) wireless personal area networks (WPANs) communication systems at 60 GHz band beam-steering antennas are needed to deal with high user random mobility and human-body shadowing characteristic of indoor environments. Similarly, beam-steering capabilities are also needed in automotive radar applications at 79 GHz, since the determination of the exact position of an object is essential for most of the functions realized by the radar sensor. In the same way, beam-scanning, which is still commonly mechanically performed nowadays, is also needed in passive imaging systems at 94 GHz. Finally, from the integration perspective, the antennas must be small, low-profile, light weight and low-cost, in order to be successfully integrated in a commercial millimeter-wave wireless system. For these reasons, many types of antenna structures have been considered to achieve high directivity and beam-steering capabilities for the aforementioned millimeter-wave communication, radar and imaging applications at 60, 79 and 94 GHz. The most part of the currently adopted solutions are based on the expensive, complex and bulky phased-array antena concept. Actually, phased-array antenna systems can scan the beam at a fast rate. However, they require a complex integration of many expensive, lossy and bulky circuits, such as solid-state phase shifters and beam-forming networks. This doctoral thesis has contributed to the study, development, and assessment of the performance of innovative antena solutions in order to improve the existing architectures at millimeter-wave frequencies, conveniently solving the problems related specifically to short-range high data rate communication systems at 60 GHz WPAN band (including future 5G millimeter-wave systems), automotive radar sensors at 79 GHz band, and communications, radar, and imaging systems at 94 GHz. The specific goals pursued in this work, focused on defining an alternative antenna architecture able to achieve a full reconfigurable 2-D beam-scanning of high gain radiation beams at millimeter-wave frequencies, has been fulfilled. In this sense, this thesis has been mainly devoted to study in depth and practically develop the fundamental part of an innovative switched-beam antenna array concept: novel inhomogeneous gradient-index dielectric flat lenses, which, despite their planar antenna profile configurations, allow full 2-D beam-scanning of high gain radiation beams. A transversal study, going from theoretical investigations, passing by numerical analysis, new fabrication strategies, performance evaluation, and to full experimental assessment of the new antenna architectures in real application environment has been successfully carried out.
Los sistemas a frecuencias de ondas milimétricas introducen una serie de requisitos muy estrictos desde el punto de vista de la antena con el objetivo de conseguir unos rendimientos específicos. En este sentido, se requieren antenas con una muy alta directividad con tal de conseguir superar las enormes pérdidas adicionales por propagación. Además, cada aplicación en concreto introduce unos requisitos adicionales. Por ejemplo, en redes de área personal de alta velocidad para sistemas de comunicación a la banda de 60 GHz, antenas con la capacidad de reconfiguración del haz de radiación son necesarias para poder tratar la problemática de la alta movilidad de los usuarios en entornos cerrados. De la misma forma, capacidades de reconfiguración de la orientación del haz de radiación son necesarias en aplicaciones relacionadas con radar de automoción a 79 GHz, dado que la determinación de la posición exacta de un objeto es esencial para muchas de las funciones del sensor de radar. De forma muy similar, la capacidad de apuntamiento del haz, que muchas veces todavía se realiza mediante sistemas mecánicos, es también imprescindible en sistemas de escaneo para aplicaciones biomédicas y de seguridad a 94 GHz. Finalmente, desde la perspectiva de la integración, las antenas deben ser eléctricamente pequeñas, ligeras, y económicas para poder ser incorporadas a un sistema inalámbrico comercial a frecuencias de onda milimétricas. Por todos estos motivos, diferentes tipos de estructuras de antenas han sido propuestos para conseguir alta directividad, junto con capacidades de reconfiguración y apuntamiento del haz de radiación para las aplicaciones anteriormente mencionadas y descritas en la banda de 60, 79, y 94 GHz. La solución tradicionalmente adoptada en este tipo de casos està estrictamente basada en el siempre caro, complejo y aparatoso concepto del phased-array. De hecho, los phased-arrays permiten el rápido escaneo de haces de radiación de alta directividad. Sin embargo, el hecho que requieran una compleja integración de muchos y caros componentes a alta frecuencia, tales como desfasadores de estado sólido o redes de conformación, los cuales introducen ciertos niveles de pérdidas, siendo además aparatosos, hacen que esta solución resulte inviable. La presente tesis doctoral contribuye al estudio, desarrollo, y ensayo experimental del rendimiento de soluciones de antenas innovadoras para la mejora de las existentes arquitecturas de antena en la banda frecuencial de las ondas milimétricas, convenientemente solucionando los problemas asociados específicamente a los sistemas de comunicación de corto alcance y alta velocidad a 60 GHz (incluyendo los futuros sistemas 5G a milimétricas), a los sistemas de radar de automoción a 79 GHz, y a los sistemas de comunicación, radar, y escaneo para aplicaciones a 94 GHz. Los objetivos específicos perseguidos en este trabajo académico, focalizados en definir una arquitectura alternativa de antena, capaz de conseguir una completa reconfiguración y escaneo de los haces de radiación en dos dimensiones del espacio a frecuencias de onda milimétricas, se han conseguido plenamente. En este sentido, esta tesis doctoral ha sido dedicada esencialmente al estudio en profundidad y desarrollo práctico de la parte fundamental del innovador concepto del switchedbeam array: nuevas lentes dieléctricas inhomogéneas de gradiente de índice con estructura plana, las cuales, a pesar de su configuración física totalmente llana, permiten una reconfiguración total, en dos dimensiones del espacio, de haces de radiación de alta directividad. Un estudio eminentemente transversal, que abarca desde la investigación teórica, pasando por el análisis numérico, nuevas metodologías y técnicas de fabricación, evaluación de rendimientos, hasta una completa caracterización y ensayo del rendimiento en entornos reales de aplicación de las nuevas arquitecturas de antena, se ha llevado a cabo con total éxito.
Els sistemes a freqüències d'ones mil·limètriques introdueixen una sèrie de requisits molt estrictes des del punt de vista de l'antena per tal d’aconseguir uns rendiments específics. En aquest sentit, es requereixen antenes amb una alta directivitat per aconseguir superar les enormes pèrdues addicionals per propagació. A més a més, cada aplicació en concret introdueix uns requeriments addicionals . Per exemple, en xarxes d'àrea personal d'alta velocitat per a sistemes de comunicació a la banda de 60 GHz, antenes amb la capacitat de reconfiguració del feix de radiació són necessàries per tal de poder tractar la problemàtica de l'alta mobilitat dels usuaris en entorns tancats . De la mateixa manera, capacitats de reconfiguració de l'orientació del feix de radiació són necessàries en aplicacions associades a radar d'automoció a 79 GHz, donat que la determinació de la posició exacta d'un objecte és essencial per moltes de les funcions portades a terme pels ens or del radar. De forma molt similar, la capacitat d'apuntament del feix, que moltes vegades encara es realitza per mitjà de sistemes mecànics, és també imprescindible en sistemes d'escaneig per aplicacions mèdiques i de seguretat a 94 GHz. Finalment, des de la perspectiva de la integració, les antenes han de ser petites en termes elèctrics, lleugeres, i econòmiques per tal de poder ser incorporades en un sistema sense fils comercial a freqüència d'ones mil·limètriques. Per aquestes raons , diversos tipus d'estructures d'antenes han sigut proposats per aconseguir alta directivitat, conjuntament amb la capacitat d'apuntament del feix de radiació per les aplicacions anteriorment descrites a les bandes de 60, 79, i 94 GHz. La solució tradicionalment adoptada en aquests casos és estrictament basada en el sempre car, complexe, i aparatós concepte del phased-array. De fet, els phased-arrays tenen la capacitat de reconfigurar a gran velocitat feixos de radiació d'alta directivitat. Tot i això, el fet que requereixin la complexa integració de molts components cars a alta freqüència, amb certs nivells de pèrdues i aparatosos, com són els desfasadors d'estat sòlid, i les xarxes de conformació, fan d'aquesta solució inviable. La present tesis doctoral contribueix a l'estudi, des envolupament, i assaig experimental del rendiment de solucions d'antenes innovadores per tal de millorar les existents arquitectures d'antena a la banda freqüencial de les ones mil·limètriques, convenientment solucionant els problemes associats específicament als sistemes de comunicació de rang proper d'alta velocitat a 60 GHz (incloent els futurs sistemes 5G a mil·limètriques ), als sistemes de radar d'automoció a la banda dels 79 GHz, i als sistemes de comunicació, radar, i escaneig per aplicacions a 94 GHz. Els objectius específics perseguits en aquest treball acadèmic, focalitzats en definir una arquitectura d'antena alternativa, capaç d'aconseguir una completa reconfiguració i escaneig dels feixos de radiació en dues dimensions de l'espaia freqüències d'ona mil·limètriques , s'han plenament aconseguit. En aquest sentit, aquesta tesis doctoral s'ha dedicat essencialment a l'estudi en profunditat i desenvolupament pràctic de la part fonamental de l'innovador concepte del switched-beam array: noves lents dielèctriques inhomogenees de gradient d'índex amb estructura planar, les quals, tot i preservar una configuració física totalment plana, permeten una reconfiguració total en dues dimensions de l'espai de feixos de radiació d'alta directivitat. Un estudi transversal, que comprèn des de la investigació teòrica, passant per l'anàlisi numèric, noves metodologies i tècniques de fabricació, avaluació de rendiments, fins a una completa caracterització i assaig del rendiment en entorns reals d'aplicació de les noves arquitectures d'antena s'ha dut a terme amb total èxit.

Il y a à l'heure actuelle un grand besoin d'antennes reconfigurables dans la bande des 60 GHz pour des applications de télédétection et de télécommunications sans fil très hauts débits. Les solutions traditionnelles de reconfiguration sont basées sur des semiconducteurs ou des composants RF-MEMS, qui connaissent un coût, une complexité et des pertes croissantes en bande millimétrique. Dans cette thèse, une approche originale a été développée : elle est basée sur la reconfiguration mécanique d'antennes et dispositifs millimétriques microrubans sur substrat élastomère ultrasouple PDMS grâce à des actionneurs MEMS grands déplacements. Premièrement, les choix de conception, la technique de simulation éléments finis (HFSS), et surtout la microfabrication d'antennes sur membrane PDMS ainsi que les techniques de mesure en impédance et rayonnement sont abordés.Deux axes ont ensuite été étudiés : les antennes accordables en fréquence, et les antennes et composants pour le balayage angulaire (déphaseurs et antennes à balayage mécanique de type scanner). Des procédés technologiques innovants ont été développés (reports de métallisations épaisses biocompatibles et d'aimants permanents en couches minces sur membrane PDMS) et différentes techniques d'actionnement (pneumatique, magnétique, par électromouillage) ont été mises en œuvre. Les performances en terme d'accord en fréquence (8,2 %) et de balayage angulaire (-90/+100°) dépassent l'état de l'art des antennes du même type en bande millimétrique, et ceci en utilisant une technologie peu complexe, ultra bas-coût et prometteuse pour la montée en fréquence.

In high frequency, high-performance wireless communications, direct line of sight antennas are common. The issue with the line of sight antennas is the need to redirect the physical antenna to achieve the best possible reception. Classical redirections are done by mechanical movements: hand tuning and motors. Our multi-functional re-configurable antenna (MRA) concept allows for electrical and non-mechanical antenna reorientation. This work investigates two important concepts in the development and enhancement of future MRA devices: special, non-interfering, control signal circuitry and nano-sized switching devices that are controlled by the special circuitry. The investigation was conducted with the use of commercially available antenna modeling software: ANSYS High Frequency System Solver.

Les systèmes de communications sans fils actuels imposent des contraintes très sévères en termes de la capacité du canal, la qualité de transmission tout en gardant les niveaux d'interférences et multi-trajets assez faibles. De telles contraintes ont rendu les antennes multifaisceaux un élément essentiel dans ces systèmes. Parmi les techniques permettant de réaliser une antenne multifaisceaux (sans avoir recours aux systèmes à balayages électroniques), un réseau d'antennes élémentaires est associé à un réseau d'alimentation (une matrice) à formation de faisceau (Beam Forming Network-BFN). Parmi les différents types de ces matrices, la matrice de Butler a reçu une attention particulière. Ceci est dû au fait qu'elle est théoriquement sans pertes et qu'elle emploie un nombre minimum de composants (coupleurs et déphaseurs) afin de générer l'ensemble de faisceaux orthogonaux demandé (avec l'hypothèse que le nombre de faisceau est une puissance de 2). Néanmoins, la matrice de Butler a un problème de conception majeur. Ce problème réside dans la structure de la matrice qui renferme des croisements ce qui a été adressé par différents travaux de recherches dans la littérature. Les Guide Intégré au Substrat (GIS) offrent des caractéristiques intéressants pour la conception des composants microondes et millimétriques faciles à intégrer sur un même support avec d'autres composants planaires. Les composants à base de GIS combinent les avantages des guides d'ondes rectangulaires, comme leur grand facteur de qualité Q, leur faibles pertes tout en étant compatible avec les technologies à faibles coûts comme le PCB et le LTCC. Vus ses caractéristiques attrayants, la technologie GIS devient un bon candidat pour la réalisation des matrices multifaisceaux faciles à intégrer avec d'autres systèmes en technologies planaires ou à base de guide GIS. Dans cette thèse, de nouveaux composants passifs sont développés en exploitant la technologie GIS en multicouches en vue de la réalisation d'une matrice de Butler 4x4 compacte et large bande. Les composants recherchés sont donc des coupleurs et des déphaseurs ayant des performances large bande en termes des amplitudes des coefficients de transmissions et les phases associés tout en gardant de faibles niveaux de pertes et de bonnes isolations. Différents techniques pour l'implémentation de déphaseurs large bande en technologie GIS sont présentés. Une nouvelle structure à base d'une propagation composite : main gauche main droite (Composite Right/Left- Handed, CRLH) dans un guide d'onde est proposée. La structure consiste d'un guide d'onde monocouche ayant des fenêtres inductives et des fentes transversales à réactances capacitives pour synthétiser l'inductance parallèle et la capacité série main gauche, respectivement. La structure est adaptée pour les réalisations de déphaseurs compacts en technologie GIS. Bien que les pertes d'insertions restent dans le même ordre de grandeur de celles des structures CRLH à base d'éléments non-localisés, ces niveaux de pertes restent relativement grands par rapport aux applications nécessitant plusieurs déphaseurs. Les déphaseurs à bases de GIS ayant des longueurs égales et des largeurs variables sont ensuite abordés. Ce type de déphaseur est effectivement très adapté à la technologie GIS qui permet des réalisations de parcours avec différentes formes (parcours droits, courbés, coudés, ..) tout en assurant des différences de phase large bande. Afin de satisfaire de faibles pertes d'insertions pour une large dynamique de phase, la longueur de ces déphaseurs est en compromis avec les variations progressives des différentes largeurs associées aux valeurs de déphasages requises. Une transition large bande, double couche et à faible perte est ainsi proposée. La transition est analysée à partir de son circuit électrique équivalent afin d'étudier les performances en termes de l'amplitude et la phase du coefficient de transmission par rapport aux différents paramètres structurels de la transition. Cette transition est ensuite exploitée pour développer un déphaseur à trois couches, large bande, en GIS. La structure consiste effectivement d'un guide d'onde replié à plusieurs reprises sur luimême selon la longueur dans une topologie trois couches à faibles pertes. De nouveaux coupleurs double couche en GIS sont également proposés. Pour les applications BFNs, une structure originale d'un coupleur large bande est développée. La structure consiste de deux guides d'onde parallèles qui partagent leur grand mur ayant une paire de fentes inclinées et décalées par rapport au centre de la structure. Une étude paramétrique détaillée est faite pour étudier l'impact des différents paramètres des fentes sur l'amplitude et la phase du coefficient de transmission. Le coupleur proposé a l'avantage d'assurer une large dynamique de couplage ayant des performances larges bandes en termes des amplitudes et les phases des coefficients de transmission avec de faibles pertes et de bonnes isolations entre le port d'entré et celui isolé. D'autre part, contrairement à d'autres travaux antérieurs et récents qui souffraient d'une corrélation directe entre la phase en transmission et le niveau de couplage, la structure proposée permet de contrôler le niveau de couplage en maintenant presque les mêmes valeurs de phase en transmission pour différents niveaux de couplage. Ceci le rend un bon candidat pour les BFNs déployant différents coupleurs telle la matrice de Nolen. Une deuxième structure originale d’un coupleur bibande est également proposée. La structure consiste de deux coupleurs concentriques en guide nervuré intégré au substrat avec un motif innovant de démultiplexage à base de GIS. Ce coupleur a été développé conjointement avec M. Tarek Djerafi de l’Ecole Polytechnique de Montréal dans un cadre de collaboration avec le Prof. Ke Wu. Finalement, pour l'implémentation de la matrice de Butler, la topologie double couche est explorée à deux niveaux. Le premier consiste à optimiser les caractéristiques électriques de la matrice, tandis que le second concerne l'optimisation de la surface occupée afin de rendre la matrice la plus compacte possible sans dégrader ses performances électriques. D'une part, la structure double couche présente une solution intrinsèque au problème de croisement permettant ainsi une plus grande flexibilité pour la compensation de phase sur une large bande de fréquence. Ceci est réalisé par une conception adéquate de la surface géométrique sur chaque couche de substrat et optimiser les différentes sections de GIS avec les différents parcours adoptés. La deuxième étape consiste effectivement à optimiser la surface sur chaque couche en profitant de la technologie GIS. Ceci consiste à réaliser des murs latéraux communs entre différents chemin électrique de la matrice en vue d'une compacité optimale. Les deux prototypes de matrices de Butler 4x4 sont optimisés, fabriqués et mesurés. Les résultats de mesures sont en bon accord avec ceux de la simulation. Des niveaux d'isolations mieux que - 15 dB avec des niveaux de réflexions inférieurs à -12 dB sont validés expérimentalement sur plus de 24% de bande autour de 12.5 GHz. Les coefficients de transmission montrent de faibles dispersions d'environ 1 dB avec une moyenne de -6.8 dB, et 10° par rapport aux valeurs théoriques, respectivement, sur toute la bande de fréquence
Multibeam antennas have become a key element in nowadays wireless communication systems where increased channel capacity, improved transmission quality with minimum interference and multipath phenomena are severe design constraints. These antennas are classified in two main categories namely adaptive smart antennas and switched-beam antennas. Switched-beam antennas consist of an elementary antenna array connected to a Multiple Beam Forming Network (M-BFN). Among the different M-BFNs, the Butler matrix has received particular attention as it is theoretically lossless and employs the minimum number of components to generate a given set of orthogonal beams (provided that the number of beams is a power of 2). However, the Butler matrix has a main design problem which is the presence of path crossings that has been previously addressed in different research works. Substrate Integrated Waveguide (SIW) features interesting characteristics for the design of microwave and millimetre-wave integrated circuits. SIW based components combine the advantages of the rectangular waveguide, such as the high Q factor (low insertion loss) and high power capability while being compatible with low-cost PCB and LTCC technologies. Owing to its attractive features, the use of SIW technology appears as a good candidate for the implementation of BFNs. The resulting structure is therefore suitable for both waveguide-like and planar structures. In this thesis, different novel passive components (couplers and phase shifters) have been developed exploring the multi-layer SIW technology towards the implementation of a two-layer compact 4×4 Butler matrix offering wideband performances for both transmission magnitudes and phases with good isolation and input reflection characteristics. Different techniques for the implementation of wideband fixed phase shifters in SIW technology are presented. First, a novel waveguide-based CRLH structure is proposed. The structure is based on a single-layer waveguide with shunt inductive windows (irises) and series transverse capacitive slots, suitable for SIW implementations for compact phase shifters. The structure suffers relatively large insertion loss which remains however within the typical range of non-lumped elements based CRLH implementations. Second, the well-known equal length, unequal width SIW phase shifters is discussed. These phase shifters are very adapted for SIW implementations as they fully exploit the flexibility of the SIW technology in different path shapes while offering wideband phase characteristics. To satisfy good return loss characteristics with this type of phase shifters, the length has to be compromised with respect to the progressive width variations associated with the required phase shift values. A twolayer, wideband low-loss SIW transition is then proposed. The transition is analyzed using its equivalent circuit model bringing a deeper understanding of its transmission characteristics for both amplitude and phase providing therefore the basic guidelines for electromagnetic optimization. Based on its equivalent circuit model, the transition can be optimized within the well equal-length SIW phase shifters in order to compensate its additional phase shift within the frequency band of interest. This twolayer wideband phase shifter scheme has been adopted in the final developed matrix architecture.This transition is then exploited to develop a three-layer, multiply-folded waveguide structure as a good candidate for compensated-length, variable width, low-loss, compact wideband phase shifters in SIW technology. Novel two-layer SIW couplers are also addressed. For BFNs applications, an original structure for a two-layer 90° broadband coupler is developed. The proposed coupler consists of two parallel waveguides coupled together by means of two parallel inclined-offset resonant slots in their common broad wall. A complete parametric study of the coupler is carried out including the effect of the slot length, inclination angle and offset on both the coupling level and the transmission phase. The first advantage of the proposed coupler is providing a wide coupling dynamic range by varying the slot parameters allowing the design of wideband SIW Butler matrix in two-layer topology. In addition, previously published SIW couplers suffer from direct correlation between the transmission phase and the coupling level, while the coupler, hereby proposed, allows controlling the transmission phase without significantly affecting the coupling level, making it a good candidate for BFNs employing different couplers, such as, the Nolen matrix. A novel dual-band hybrid ring coupler is also developed in multi-layer Ridged SIW (RSIW) technology. This coupler has been jointly developed with Tarek Djerafi in a collaboration scenario with Prof. Ke Wu from the Ecole Polytechnique de Montréal. The coupler has an original structure based on two concentric rings in RSIW topology with the outer ring periodically loaded with radial, stub-loaded transverse slots. A design procedure is presented based on the Transverse Resonance Method (TRM) of the ridged waveguide together with the simple design rules of the hybrid ring coupler. A C/K dual band coupler with bandwidths of 8.5% and 14.6% centered at 7.2 GHz and 20.5 GHz, respectively, is presented. The coupler provides independent dual band operation with low-dispersive wideband operation. Finally, for the Butler matrix design, the two-layer SIW implementation is explored through a two-fold enhancement approach for both the matrix electrical and physical characteristics. On the one hand, the two-layer topology allows an inherent solution for the crossing problem allowing therefore more flexibility for phase compensation over a wide frequency band. This is achieved by proper geometrical optimization of the surface on each layer and exploiting the SIW technology in the realization of variable width waveguides sections with the corresponding SIW bends. On the other hand, the two-layer SIW technology is exploited for an optimized space saving design by implementing common SIW lateral walls for the matrix adjacent components seeking maximum size reduction. The two corresponding 4×4 Butler matrix prototypes are optimized, fabricated and measured. Measured results are in good agreement with the simulated ones. Isolation characteristics better than -15 dB with input reflection levels lower than -12 dB are experimentally validated over 24% frequency bandwidth centered at 12.5 GHz. Measured transmission magnitudes and phases exhibit good dispersive characteristics of 1dB, around an average value of -6.8 dB, and 10° with respect to the theoretical phase values, respectively, over the entire frequency band

Mestrado em Engenharia Electrónica e Telecomunicações
The adoption and proliferation of information systems in many business and personal activities leads to the need of tagging and tracking items and services. Radio frequency identi cation (RFID) systems were developed as an e ort to answer the increasing needs of particulars and enterprises alike for wireless identi cation of objects and data exchange services, enabling a large number of businesses to reduce costs and increase revenue. As to further develop the e ciency provided by businesses worldwide, smart antenna systems were introduced as core component in their production and service providing lines, opening the path for innovative and robust wireless RFID based communication schemes, providing advanced signal capturing, processing characteristics and enhanced tracking and process automation. Smart antennas can be installed within RFID readers, enabling them to more e ciently process returned echoes by the tags and therefore improving the identi cation mechanism. RFID reader architectures with an embedded smart antenna network reliably improve the throughput, the reading speed and position detection of tagged items. A smart antenna based circuit is proposed here for RFID assisted localization and for beam steering applications using a uniform linear array of microstrip directional antennas. Several beamforming and direction of arrival estimation methods were employed in order to analyze their performance and resolution based on the computational load, modulation, and the overall environment in which the smart anetnna system may be deployed.
A adoção e proliferação de sistemas de informação em várias indústrias e atividades pessoais são responsáveis pela crescente necessidade de identifcar e rastrear itens e serviços. Sistemas de identificação por rádiofrequência (RFID) foram desenvolvidos de modo a responder às crescentes necessidades tanto de particulares como de empresas quanto à utilização de sistemas de identificaçao e de transmissão de dados sem _os, permitindo a redução de despesas e o aumento de receitas a várias empresas. De modo a melhorar a eficiência de empresas a uma escala global, sistemas de antenas inteligentes foram introduzidos nas suas linhas de manufatura e de prestação de serviços como um componente central, abrirando o caminho para esquemas de comunicação sem _os inovadores e robustos, baseados em RFID, facultando processos de captura e processamento de sinal avançados capazes de fornecer melhorias em aplicações de rastreamento e automação de processos. Antenas inteligentes podem ser instaladas em leitores RFID, permitindo um melhor processamento de sinais transmitidos pelas etiquetas, dando origem a um método de identificação mais eficiente. A arquitectura de leitores RFID com uma rede de antenas inteligentes embutida garante melhorias na taxa de transferência e na rapidez de leitura de informação assim como na deteção de itens etiquetados. Um circuito baseado em sistemas de antenas inteligentes é proposto neste trabalho para localização assistida dispositivos RFID e para direccionamento de feixe através da utilizaçao de um agregado linear e uniforme de antenas microstrip diretivas. Várias técnicas de direcionamento de feixe e de estimativa de angulo de chegada foram utilizados, de modo a analisar o desempenho e a resolução de cada algoritmo de acordo com a carga computacional, modulação utilizada e o ambiente em que o sistema de antenas inteligentes poderá ser implementado.

Phased array weather radar antennas with beam steering capabilities are suitable alternatives to weather radars with mechanically scanning reflector antennas. Dual-polarized phased-array weather radar antennas, however, demand careful assessment of the x-polar characteristics. The low x-pol radiation of polarimetric weather radar antennas is of significant importance for the proper classification and qualitative estimation of hydrometeors in illuminate volumes. Unfortunately, array antennas display changing x-pol contributions during the electronical beam steering process. Typically, the x-pol radiation will be substantially increased in the co-polar main beam direction but also in other angular directions. Consequently, it is a vital challenge to design arrays with low x-pol contribution during beam steering. In this dissertation a new phased-array weather radar concept is developed. The phased array system configuration can be used to substitute state-of-the-art weather radars with reflector antennas. Furthermore, a dense network of these phased-array radars can be used to substitute a network of high power weather radars, which are used nowadays. The research focus of this work is the development of a dual-polarized microstrip patch antenna with phased-array capability and very high polarization purity. In this regard, new graphical techniques are developed to investigate the causes and the reduction of the x-pol radiation of isolated (stand-alone) microstrip patch antennas. To further reduce the x-pol contribution of antennas, optimization methods have been investigated, evaluated and developed. For the first time in literature, differential-feed antenna arrays are compared to excitation optimized single-feed antenna arrays in their x-pol contribution in the boresight direction and during beam steering. In particular, two dual-polarized 4x8 antenna arrays have been developed and simulated by CST MWS, produced as multilayer PCB and verified at the compact antenna test range at RWTH Aachen. The results show that the x-pol contributions of arrays are significantly reduced for differentially-feed antenna arrays, even when beam steering is performed. During the azimuth scan of 120_ a record setting x-pol suppression of -45 dB and -36 dB could be measured for the horizontal and vertical polarization channels, respectively.
Wetterradarsysteme mit phasengesteuerten Antennen stellen eine echte Alternative zu Wetterradarsystemen mit mechanisch drehenden Reflektorantennen dar. Dual-polarisierte phasengesteuerte Antennen müssen jedoch sehr genau in ihrem Kreuzpolarisationsverhalten verifiziert werden, um für den Wetterradarbereich von Nutzen zu sein. Die Unterdrückung der kreuzpolaren Anteile von Radarantennen ist von fundamentaler Bedeutung, um Hydrometeore mit Hilfe von polarimetrischen Wetterradarsystemen klassifizieren und qualitativ bestimmen zu können. Die hohe Anforderung an Polarisationsreinheit ist mit aktuell erhältlichen Arraydesigns nur schwierig zu realisieren, da sich die Kreuzpolarisationsunterdrückung während des elektronischen Schwenks der Hauptkeule signifikant verschlechtert. Diese Dissertation stellt ein Wetterradar Systemkonzept mit phasengesteuerter Gruppenantenne vor, welches die aktuell genutzten Wetterradare mit Reflektorantennen ablösen könnte. Der Fokus der Arbeit wurde auf die Entwicklung einer Dual-polarimetrischen, polarisationsreinen und phasengesteuerten Mikrostreifenleiterantennen gelegt. Hierbei wurden neue grafische Verfahren entwickelt, die es ermöglichen, die Generierung der kreuzpolaren Anteile von isolierten Patchantennen (Einzelpatche) zu erklären und zu minimieren. Um die kreuzpolaren Anteile weiter herabzusetzen wurden Optimierungsverfahren für Arrayantennen erforscht, bewertet und neu entwickelt. Zum ersten Mal wurden differentiell gespeiste mit einzeln gespeisten Antennenarrays in ihrem Kreuzpolarisationsverhalten während des elektronischen Schwenks der Hauptkeule verglichen. Zwei Dual- polarimetrische 4x8 Antennenarrays (differentiell gespeist und mit optimierter Phasenansteuerung) wurden zu diesem Zweck mittels CST MWS entworfen, simuliert, als Multilagenplatine gefertigt und an der Antennentestanlage der RWTH Aachen vermessen. Die Resultate zeigen, dass die Kreuzpolarisationsanteile bei differentiell gespeisten Mikrostreifenleiterantennen in Gruppenkonfiguration, selbst beim elektronischen Schwenk der Hauptkeule, signifikant minimiert werden konnten. Für einen azimutalen Scanbereich von 120_ konnte eine exzellente Kreuzpolarisationsunterdrückung zwischen -45 dB und -36 dB messtechnisch für den horizontalen und vertikalen Polarisationskanal nachgewiesen werden.

The application of adaptive communication techniques for mobile communications has attracted considerable interest in the last decade. One example of these techniques is spatial filtering through planar antenna array beam forming. This thesis describes the development of a digital system that adaptively controls a phased array antenna. The radiating structure of the phased antenna array is tetrahedral-shaped and contains four antenna elements on each of its three faces. The overall system comprises of a digital control board with an external computer interface, an RF control board, and the phased antenna array. The RF controls the main lobe direction on the phased array antenna. This thesis describes the design and implementation of the digital control board. The digital control board`s primary responsibilities are implementing inter- faces between the external computer and the RF board, which results in two operational modes: the MATLAB graphical user interface (GUI) mode and the adaptive receive mode. The GUI mode allows users to input parameters that provide interactive control of the phased antenna array by interfacing with an external computer and the RF control board. The adaptive receive mode im- plements an algorithm for an adaptive receive station. This algorithm uses a 58-point scanning technique that locates the maximum receive power direction. Test results show that the digital control board successfully manages the RF board control voltage with an nominal error of less than 1%, which subsequently allows for precise control of the antenna`s active face. Additionally, testing of the GUI demonstrated the successful interactive application of various system control parameters.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: A joint project between the KU Leuven and Stellenbosch Universities was at the time of this thesis underway to develop a space borne electronically beam steerable antenna and the associated ground-space segments. This thesis covers the development of an aircraft based satellite emulator to facilitate convenient aircraft based testing of an antenna array, intended for low earth orbit satellite deployment and subsystems to control the antenna array. A flight strategy is developed to emulate such a satellite pass as best possible, with the strategy implemented in software on in-flight PC hardware. A full interface between the aircraft avionics and satellite bus system has been developed to enable generation of the required antenna steering commands and to create a satellite bus image to the payload. Successful test results are presented, as obtained from the actual aircraft ight simulator. The thesis describes the successful development and testing of a low altitude flight test strategy for certain satellite borne systems, as a cost-effective and realistic interim step to actual and very expensive space flight testing.
AFRIKAANSE OPSOMMING: 'n Gesamentlike projek deur KU Leuven en Stellenbosch Universiteit was tydens die verloop van hierdie tesis besig met die ontwikkeling om 'n ruimte gebaseerde elektroniese straal beheerde antenna en geassosieerde substelsels daar te stel. Hierdie tesis handel oor die ontwikkeling van 'n vliegtuig gebaseerde satelliet emulator om die toetsing van 'n elektroniese stuurbare antenna, wat bedoel is vir 'n lae aardse wentelbaan, te fasiliteer en die ontwikkeling van substelsels wat die stuurbare antenna beheer. 'n Vlug strategie is ontwikkel om so 'n satelliet wentelbaan so na as moontlik te emuleer. Die strategie word dan geïmplementeer in die sagteware van die aanboord vlug rekenaar. 'n Intervlak tussen die vliegtuig instrumente en satellietbus is ontwikkel om die generering van die nodinge instruksies te fasiliteer en om 'n virtuele satellietbus vir die res van die satelliet stelsel te skep. Suksesvolle toets resultate word getoon wat met behulp van 'n vliegtuig simulator verkry is. Die tesis beskryf die suksesvolle ontwikkeling en toetsing van 'n lae vlugtoets strategie vir satelliet stelsels, as 'n koste effektiewe en realistiese tussenstap, tot baie duur ruimte vlugtoetsing.

The thesis presents a compact, miniature, and low cost antenna array designed for millimeter-wave frequencies for future 5th generation (5G) mobile applications. The proposed antenna array is a geometrically modified structure of the Franklin array, which allowed to transform a conventional narrowband array into a wideband antenna array. It is composed of five millimetre-wave circular patch radiation elements with phasing stubs. The designed array, fabricated on the commercial Rogers RO3003 substrate with small form factor of 8x25x0.5 mm3, covers the upcoming 5G band of 23.6-30.3 GHz, with peak gain as 10.8 dB, and high radiation efficiency over the whole operating band. In addition, with frequency sweeping, the proposed antenna array radiation pattern is directive and offers beam steering at the desired angles, acting similarly as a leaky-wave antenna.

Phased arrays eliminate the problems of mechanical steering by using fast and reliable electronic components for steering the main beam. Modeling and simulation of beam steering for 1D and 2D arrays is the aspect that is considered in this thesis. A 1D array with 4 elements and a 2D array with 16 elements are studied in the X-band (8-12 GHz). The RF front-end of a phased array radar is modeled by means of ADS Momentum (Advanced design system).

International Telemetering Conference Proceedings / October 26-29, 1987 / Town and Country Hotel, San Diego, California
A recently tested antenna pointing control system for gimbaled antennas has been developed. A modified TDRSS user transponder produces pointing error signals from the S-band forward link which in turn drive the Steering Control Electronics (SCE) to precision steer a S-/Ku-band Data and S-band Tracking (KDST) planar array. A successful test of the pointing and data handling capabilities is described and plans for further tests, incorporating additional refinements, are presented.

Traditional antennas have a lot of limitations as their performance is usually fixed by their initial geometry. On the other hand, modern communication systems are getting way to complicated compared to their earlier counterparts. This necessitates some special types of smart or reconfigurable antennas, which can dynamically adapt to the requirements of the communication systems more effectively. Using conventional single functional antennas is therefore not an efficient approach in these sort of communication systems. Considering all these factors, in this thesis, a beam steerable reconfigurable antenna system is presented that can yield the radiation patterns of multiple antennas with a single structure, necessary for 5G communication. This antenna system occupies comparatively much smaller space and can provide highly directive gain at different directions. It is expected that- in near future, further improvements of this type of antenna system can be performed to pave the way for some additional necessary functions required in modern communication systems.

International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, Nevada
Two different types of tracking feeds are currently used in the majority of telemetry tracking antenna systems when autotrack operation is required. They are of the conical scanner or of the single channel monopulse family and they employ well known technologies. In broadband applications, these feeds all suffer from the same inherent degradation in efficiency caused by their inability to maintain a constant crossover loss value and by their failure to properly illuminate the reflector. In high dynamics situations they can also generate unwanted and sometimes detrimental modulation whenever on-axis tracking is not maintained. In addition, currently available versions of the conical scanner are not capable of high scan rates or of scan rate agility and they are ill-suited for use in tracking systems based on non-orthogonal axes positioners. This paper describes a new high efficiency tracking feed system based on proven conical scanner technology. Its design incorporates features such as variable crossover, steerable beam, high scan rates, scan rate agility as well as stable reference coordinate system. In addition to these features, this new feed is also capable of delivering, in all but one operational category, levels of performance superior to that achievable to date by any other implementation of the conical scanner or of the single channel monopulse technology.

Thesis (PhD (Electrical Engineering))--Cape Peninsula University of Technology, 2019
This dissertation presents a concept for a compact, low-profile, integrated solar panel antenna for use on small satellites in low Earth orbit. To date, the integrated solar panel antenna design approach has primarily been, patch (transparent or non-transparent) and slot radiators. The design approach presented here is proposed as an alternative to existing designs. A prototype, comprising of an optically transparent rectangular dielectric resonator was constructed and can be mounted on top of a solar panel of a Cube Satellite. The ceramic glass, LASF35 is characterised by its excellent transmittance and was used to realise an antenna which does not compete with solar panels for surface area. Currently, no closed-form solution for the resonant frequency and Q-factor of a rectangular dielectric resonator antenna exists and as a first-order solution the dielectric waveguide model was used to derive the geometrical dimensions of the dielectric resonator antenna. The result obtained with the dielectric waveguide model is compared with several numerical methods such as the method of moments, finite integration technique, radar cross-section technique, characteristic mode analysis and finally with measurements. This verification approach was taken to give insight into the resonant modes and modal behaviour of the antenna. The interaction between antenna and a triple-junction gallium arsenide solar cell is presented demonstrating a loss in solar efficiency of 15.3%. A single rectangular dielectric resonator antenna mounted on a ground plane demonstrated a gain of 4.2 dBi and 5.7 dBi with and without the solar cell respectively. A dielectric resonator antenna array with a back-to-back Yagi-Uda topology is proposed, designed and evaluated. The main beam of this array can be steered can steer its beam ensuring a constant flux density at a satellite ground station. This isoflux gain profile is formed by the envelope of the steered beams which are controlled using a single digital phase shifter. The array achieved a beam-steering limit of ±66° with a measured maximum gain of 11.4 dBi. The outcome of this research is to realise a single component with dual functionality satisfying the cost, size and weight requirements of small satellites by optimally utilising the surface area of the solar panels.

L’apparition des objets connectés intelligents dont nous sommes les témoins depuis quelques années a généré un besoin croissant d’antennes à bas coût et énergétiquement sobres. La capacité d’effectuer à la volée une mise en forme du faisceau où sa reconfiguration est une propriété particulièrement intéressante, qui pourrait permettre à l’objet intelligent d’effectuer des tâches telles que la surveillance de zone par exemple ou bien d’optimiser son bilan de liaison en ne visant qu’une seule direction de l’espace. Cela pourrait également mener à un accroissement de l’autonomie de l’objet, via une diminution de sa consommation énergétique, voir à le rendre totalement indépendant s’il devient suffisamment économe pour envisager son alimentation via des systèmes de récupération d’énergie. C’est dans ce contexte que nous proposons ici une nouvelle architecture d’antenne reconfigurable, capable d’un balayage de faisceau sur 360° degrés et basée sur l’utilisation de métal liquide au sein d’un système d’actionnement microfluidique. Dans le premier chapitre, nous ferons une rapide présentation des deux principales technologies de balayage de faisceau utilisées aujourd’hui avant d’étudier les diverses techniques de déplacement de métal liquide utilisées et documentées dans la littérature. L’objectif de ce travail est de sélectionner la technique la plus adaptée à nos besoins. Dans le second chapitre, nous proposerons les deux designs d’antennes envisagés pour notre système, basés sur l’architecture Yagi-Uda. Nous discuterons des avantages et inconvénients de chacun afin d’en sélectionner un qui sera examiné plus en avant dans le chapitre suivant. Dans le troisième chapitre, nous étudierons, à l’aide de simulations électromagnétiques, les performances du design d’antenne sélectionné dans le but de justifier notre choix. Cette étude se concentrera sur l’implémentation graduelle de la complexité du design retenu, en partant d’un système très théorique pour aboutir à une émulation très proche de ce que pourrait être un prototype final. Finalement, dans le quatrième et dernier chapitre nous considérerons deux preuves de concept du système complet ainsi que leurs différentes techniques de fabrications. Étant donné le fait que chaque preuve de concept se concentre soit sur l’aspect RF ou fluidique du système, nous étudierons aussi leurs performances respectives. Nous détaillerons également le développement de certains procédés de fabrication spécifiques utilisés pour réaliser les briques de base, en particulier les objets micro-fluidiques. Ce chapitre nous permet de conclure positivement cette étude de la faisabilité du concept proposé et développé dans ce travail
The advent of autonomous connected smart objects we are witnessing since a few years has generated a growing need for low cost and energetically sober reconfigurable antennas. The ability to perform on the fly beam shaping and re-configuration is a particularly interesting property which would allow the smart object to perform task such as area surveillance for example and to optimize its link budget by targeting a specific direction of space. This could also allow the increase of the object’s autonomy, through a diminution of its power consumption, or even to render it fully autonomous if it becomes sober enough to envision the use of energy harvesting systems. It is in this context that we propose here a new reconfigurable antenna architecture, capable of 360° beam steering, based on the use of liquid metal within a microfluidic actuation system.In the first chapter, we will do a quick presentation of today’s two main beam steering technics used for antennas before studying the various used and documented technics of liquid metal displacement used in the literature for RF applications. The objective is to single out the better suited one to our requirements.In the second chapter, we will propose the two antenna designs envisioned for our system, based on the Yagi-Uda architecture. We will discuss the advantages and drawbacks of each in order to select one design which will be more closely investigated on the following chapter.In the third chapter, we will study, with the help of electromagnetic simulations, the performances of this selected antenna design in order to justify our choice. This study will focus on the gradual complexity implementation of the chosen design, from a very theoretical system to one very close to what a final prototype would be. Finally, in the fourth and last chapter we will consider two proofs of concept of the complete system and their various fabrications technics. Given that each proof of concept focus either on the RF or the fluidic aspect of the system, we will investigate their performances. We will also detail the development of some of the specific fabrication processes used for the basic building blocks, especially for the fluidic objects. This chapter allow us to conclude positively this study on the feasibility of this concept which was proposed and developed in this work

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, May, 2020
Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 105-106).
We investigate the feasibility of using a series of deformable liquid lenses to achieve wide-angle beam steering for CubeSat laser communication (lasercom) crosslinks. Liquid lenses are lenses that can non-mechanically alter focal length based on an applied voltage or current. We evaluate two commercial liquid lens manufacturers, Corning Varioptic and Optotune. Corning Varioptic lenses rely on the principle of electrowetting for lens actuation, while Optotune lenses are driven by a voice coil. For steering, a liquid lens is placed offset from the optical axis. Varying the liquid lens focal length will cause the beam to steer in 1D by refraction, but also causes a change in beam divergence. Adding an on-axis focusing liquid lens allows this beam divergence to be controlled dynamically. Adding a second off-axis liquid lens, displaced in the other axis, creates 2D steering. A fisheye lens can then amplify the steering cone to full hemispherical coverage [1].
However, liquid lenses were not designed for nor have ever been flown in space. In this work, we show that both types of liquid lens passed initial space qualification testing. Testing activities included vacuum survivability, vacuum operation, and thermal-vacuum (TVAC). The Corning A39N0 and Optotune EL-16-40-TC liquid lenses provided nearly identical steering transfer functions in vacuum as in ambient. The Corning and Optotune lenses achieved 2.7° and 8.6° angular range with collimated output, respectively, although these ranges were truncated by the camera field of view and focusing lens optical power range. The steering curves were linear, so, allowed to steer their full range, approximately 4.3° and 21.5° of steering range can be expected. In TVAC, the Corning lens operated from -25°C to 75°C and the Optotune lens from -40°C to 70°C. The lenses never failed in this testing, rather, external factors forced the termination of testing.
Thus, even more temperature range may be expected. The lens steering angles drifted with temperature at 0.24 mrad/°C for the A39N0 and 0.19 mrad/°C for the EL-16-40-TC. The worst case hysteresis error, the difference in the steering transfer function between increasing and decreasing input values, was 0.3 mrad for the Corning lens and 1 mrad for the Optotune lens. A beam quality analysis was conducted in Zemax to identify the impact of beam refraction through the liquid lenses on transmit gain. Worst case values for transmit losses were found to be -0.5 dB for the Corning lens and -0.4 dB for the Optotune lens. However, at positive steering angles, an overall transmit boost can be expected due to the impact of beam expansion through the focusing liquid lens. We discuss key terminal design trade-offs, and a prototype transmit-only terminal was created and demonstrated full hemispherical steering in a lab setting.
Future testing will investigate the beam quality and divergence for wide angle steering to quantify link distances for free space optical communications using this method of beam steering. A compact hemispherical laser transceiver will enable efficient, high data rate lasercom for small satellites.
by Faisal A. Fogle.
S.M.
S.M. Massachusetts Institute of Technology, Department of Aeronautics and Astronautics

The objectives of this work were to investigate, design and implement beam steering antenna arrays for mobile and wireless applications using the genetic algorithm (GA) and particle swarm optimisation (PSO) techniques as optimisation design tools. Several antenna designs were implemented and tested: initially, a printed dipole antenna integrated with a duplex RF switch used for mobile base station antenna beam steering was investigated. A coplanar waveguide (CPW) to coplanar strip (CPS) transition was adopted to feed the printed dipole. A novel RF switch circuit, used to control the RF signal fed to the dipole antenna and placed directly before it, was proposed. The measured performance of the RF switch was tested and the results confirmed its viability. Then two hybrid coupled PIN diode phase shifters, using Branchline and Rat-Race ring coupler structures, were designed and tested. The generation of four distinct phase shifts was implemented and studied. The variations of the scattering parameters were found to be realistic, with an acceptable ±2 phase shift tolerance. Next, antenna beam steering was achieved by implementing RF switches with ON or OFF mode functions to excite the radiating elements of the antenna array. The switching control process was implemented using a genetic algorithm (GA) method, subject to scalar and binary genes. Anti-phase feeding of radiating elements was also investigated. A ring antenna array with reflectors was modelled and analysed. An antenna of this type for mobile base stations was designed and simulation results are presented. Following this, a novel concept for simple beam steering using a uniform antenna array operated at 2.4 GHz was designed using GA. The antenna is fed by a single RF input source and the steering elements are reactively tuned by varactor diodes in series with small inductors. The beam-control procedure was derived through the use of a genetic algorithm based on adjusting the required reactance values to obtain the optimum solution as indicated by the cost function. The GA was also initially used as an optimisation tool to derive the antenna design from its specification. Finally, reactive loading and time modulated switching techniques are applied to steer the beam of a circular uniformly spaced antenna array having a source element at its centre. Genetic algorithm (GA) and particle swarm optimisation (PSO) processes calculate the optimal values of reactances loading the parasitic elements, for which the gain can be optimised in a desired direction. For time modulated switching, GA and PSO also determine the optimal on and off times of the parasitic elements for which the difference in currents induced optimises the gain and steering of the beam in a desired direction. These methods were demonstrated by investigating a vertically polarised antenna configuration. A prototype antenna was constructed and experimental results compared with the simulations. Results showed that near optimal solutions for gain optimisation, sidelobe level reduction and beam steering are achievable by utilising these methods. In addition, a simple switching process is employed to steer the beam of a horizontally polarised circular antenna array. A time modulated switching process is applied through Genetic Algorithm optimisation. Several model examples illustrate the radiation beams and the switching time process of each element in the array.

The objectives of this work were to investigate, design and implement beam steering antenna arrays for mobile and wireless applications using the genetic algorithm (GA) and particle swarm optimisation (PSO) techniques as optimisation design tools. Several antenna designs were implemented and tested: initially, a printed dipole antenna integrated with a duplex RF switch used for mobile base station antenna beam steering was investigated. A coplanar waveguide (CPW) to coplanar strip (CPS) transition was adopted to feed the printed dipole. A novel RF switch circuit, used to control the RF signal fed to the dipole antenna and placed directly before it, was proposed. The measured performance of the RF switch was tested and the results confirmed its viability. Then two hybrid coupled PIN diode phase shifters, using Branchline and Rat-Race ring coupler structures, were designed and tested. The generation of four distinct phase shifts was implemented and studied. The variations of the scattering parameters were found to be realistic, with an acceptable ±2 phase shift tolerance. Next, antenna beam steering was achieved by implementing RF switches with ON or OFF mode functions to excite the radiating elements of the antenna array. The switching control process was implemented using a genetic algorithm (GA) method, subject to scalar and binary genes. Anti-phase feeding of radiating elements was also investigated. A ring antenna array with reflectors was modelled and analysed. An antenna of this type for mobile base stations was designed and simulation results are presented. Following this, a novel concept for simple beam steering using a uniform antenna array operated at 2.4 GHz was designed using GA. The antenna is fed by a single RF input source and the steering elements are reactively tuned by varactor diodes in series with small inductors. The beam-control procedure was derived through the use of a genetic algorithm based on adjusting the required reactance values to obtain the optimum solution as indicated by the cost function. The GA was also initially used as an optimisation tool to derive the antenna design from its specification. Finally, reactive loading and time modulated switching techniques are applied to steer the beam of a circular uniformly spaced antenna array having a source element at its centre. Genetic algorithm (GA) and particle swarm optimisation (PSO) processes calculate the optimal values of reactances loading the parasitic elements, for which the gain can be optimised in a desired direction. For time modulated switching, GA and PSO also determine the optimal on and off times of the parasitic elements for which the difference in currents induced optimises the gain and steering of the beam in a desired direction. These methods were demonstrated by investigating a vertically polarised antenna configuration. A prototype antenna was constructed and experimental results compared with the simulations. Results showed that near optimal solutions for gain optimisation, sidelobe level reduction and beam steering are achievable by utilising these methods. In addition, a simple switching process is employed to steer the beam of a horizontally polarised circular antenna array. A time modulated switching process is applied through Genetic Algorithm optimisation. Several model examples illustrate the radiation beams and the switching time process of each element in the array.

Il y a à l’heure actuelle un grand besoin d’antennes reconfigurables dans la bande des 60 GHz pour des applications de télédétection et de télécommunication sans fil. Les solutions traditionnelles de reconfiguration sont basées sur des semi-conducteurs ou des composants RF-MEMS conventionnels dont le coût, la complexité et les pertes croissent avec la fréquence.Dans cette thèse une approche originale a été développée : elle est basée sur la reconfiguration mécanique d’antennes et de dispositifs sur substrat élastomère souple PDMS et l’utilisation d’actionneurs MEMS grand déplacement.L’histoire et le contexte de la télécommunication sont abordés pour faire comprendre l’intérêt récent pour la communication à 60 GHz ainsi que la nécessité de la reconfiguration et l’avantage de la reconfiguration mécanique à cette fréquence. Le PDMS, polymère ultra-souple de choix est ensuite étudié en détail. Il est caractérisé mécaniquement et diélectriquement. Sont ensuite présenté les applications développées par cette approche : des antennes accordables en fréquence ainsi que des dispositifs permettant un balayage de l’espace. Différents mode d’actionnement (pneumatique, magnétique, interaction électro-fluidique) sont explorés
There is an increasing need for tunable antennas in the 60 GHz band for remote sensing application and wireless communication. Traditional tuning solutions are based on semiconductor or conventional RF-MEMS but these component face cost, complexity and losses issues at millimeter waves. In this thesis, an original approach was developed: it is based on the mechanical reconfiguration of millimeter wave microstrip antennas and devices printed on ultrasoft elastomeric PDMS substrate, thanks to large displacement MEMS actuators.First, a quick history and context on the telecommunication explain the recent interest toward the 60 GHz band for telecommunication and the need for tenability and advantage of mechanical tenability at this frequencies. The ultrasoft polymeric PDMS is then studied. It is caracterised both mechanically and dielectrially. Then the different applications developed during this thesis are presented: frequency tunable antenna and beam steering systems. Different actuation solution (pneumatic, magnetic, electro-fluidic interaction) are explored

Ce mémoire est consacré à l’étude et au développement d’un nouveau système antennaire agile en rayonnement appelé MARPEM (Matrice Agile Rayonnante à Pixels Elaborés en Métamatériaux). Ce système est formé d’une matrice planaire formée par un agencement jointif de pixels électromagnétiques. Le concept du pixel est inspiré de l’antenne à Bande Interdite Electromagnétique et entouré par une enceinte murale. Ces pixels sont alimentés par des circuits de formation de faisceaux.Des études théoriques approfondies ont montré des performances électromagnétiques de MARPEM concernant le faible couplage mutuel, les forts pointages électroniques et l’élimination de lobes de réseau. Trois prototypes ont été étudiés et réalisés afin de valider expérimentalement les performances de MARPEM et de répondre aux exigences de différentes applications
This PhD thesis is dedicated to the study and the development of a novel agile antenna system called ‘Agile Radiating Matrix with Metamaterials Pixels’. This system is formed by a planar matrix which is composed by an association of jointed electromagnetic pixels. The pixel design is inspired from the electromagnetic band gap antenna and it is surrounded by metallic walls. These pixels are fed by means of several beam forming networks.The intensive theoretical study made on the matrix antenna, showed several electromagnetic performances concerning the low mutual coupling, the great beam steering for high scanning angles and the elimination of grating lobes. Three manufactured prototypes are presented in order to experimentally validate the matrix performances and to respond to some application requirements

The development of phased array antenna systems requires considerable resources and time. Due to this constraint, the Naval Air Command (NAVAIR) needs a phased array that can be physically reconfigured to meet the demands of multiple missions without added development time or cost. This work develops and demonstrates a solution to this problem by implementing an adaptive calibration approach to the development of electronically steerable antennas (ESAs). In contrast to previous analog adaptive beamformer systems, this system allows for an arbitrary antenna configuration with a variable number of antenna elements and locations. A simulation model of arbitrary phased array configurations was developed to test the beamformer calibration algorithm and was used to show practical tile locations. To demonstrate this approach, four 4x4 ULA phased array antenna tiles were built and tested together in various configurations to show the viability of developing a physically reconfigurable phased array system.

This thesis discusses optoelectronic devices at mm-wave frequencies, focusing on optoelectronic beamforming and non-mechanical beam steering based on an optically excited Fresnel zone plate plasma. The optically controlled zone plate, termed the photo-injected Fresnel zone plate antenna (piFZPA) within this work, is introduced and a comprehensive theoretical framework developed. The design and optimisation of Fresnel zone plates are detailed, which determine the inherent performance of the piFZPA. A range of zone plates were designed, fabricated, and characterised at 94 GHz with up to 46 dBi gain, -26 dB sidelobe levels, and 67% aperture efficiency being measured for a quarter-wave design. The control of (sub) mm-wave beams by optical modulation of the complex permittivity of a semiconductor substrate is discussed. The significance of the free-carrier plasma dynamics, the effective lifetime, surface recombination, and the limits of the substrate which are imposed by the spatial resolution of the free-carrier plasma are highlighted, with the optimisation of these parameters discussed. The passivation quality of high-resistivity silicon wafers were characterised using a mm-wave photoconductance decay method, which yielded lifetime improvements from τ[subscript(eff)] = 60 us up to τ[subscript(eff)] ≈ 4,000 us, resulting in lowered recombination velocities (S = 15 cm/s). W-band characterisations of the passivated wafers illustrate the significance of surface recombination, with measured attenuations of up to 24 dB. Novel theoretical models are developed throughout this thesis, which yield insight into the requirements of optoelectronic devices, and are shown to agree well with measured data. The theoretical framework developed details the requirements, limitations, suitability, and design of piFZPAs at any frequency. A range of transmission-type piFZPAs are demonstrated and characterised at 94 GHz, both on-axis and off-axis, based on a novel architecture, with up to 8% aperture efficiency. Finally, the hybridisation of the piFZPA technique and well established visible display technologies, which has been developed throughout this thesis, enable low-cost, simple, and highly flexible optoelectronic devices, highlighting this method as an attractive solution to adaptive beamforming and non-mechanical steering at mm-wave and submm-wave frequencies.

This dissertation proposes, studies and experimentally demonstrates novel liquid crystal (LC) optics to solve challenging problems in RF and photonic signal processing, freespace and fiber optic communications and microscopic imaging. These include free-space optical scanners for military and optical wireless applications, variable fiber-optic attenuators for optical communications, photonic control techniques for phased array antennas and radar, and 3-D microscopic imaging. At the heart of the applications demonstrated in this thesis are LC devices that are non-pixelated and can be controlled either electrically or optically. Instead of the typical pixel-by-pixel control as is custom in LC devices, the phase profile across the aperture of these novel LC devices is varied through the use of high impedance layers. Due to the presence of the high impedance layer, there forms a voltage gradient across the aperture of such a device which results in a phase gradient across the LC layer which in turn is accumulated by the optical beam traversing through this LC device. The geometry of the electrical contacts that are used to apply the external voltage will define the nature of the phase gradient present across the optical beam. In order to steer a laser beam in one angular dimension, straight line electrical contacts are used to form a one dimensional phase gradient while an annular electrical contact results in a circularly symmetric phase profile across the optical beam making it suitable for focusing the optical beam. The geometry of the electrical contacts alone is not sufficient to form the linear and the quadratic phase profiles that are required to either deflect or focus an optical beam. Clever use of the phase response of a typical nematic liquid crystal (NLC) is made such that the linear response region is used for the angular beam deflection while the high voltage quadratic response region is used for focusing the beam. Employing an NLC deflector, a device that uses the linear angular deflection, laser beam steering is demonstrated in two orthogonal dimensions whereas an NLC lens is used to address the third dimension to complete a three dimensional (3-D) scanner. Such an NLC deflector was then used in a variable optical attenuator (VOA), whereby a laser beam coupled between two identical single mode fibers (SMF) was mis-aligned away from the output fiber causing the intensity of the output coupled light to decrease as a function of the angular deflection. Since the angular deflection is electrically controlled, hence the VOA operation is fairly simple and repeatable. An extension of this VOA for wavelength tunable operation is also shown in this dissertation. A LC spatial light modulator (SLM) that uses a photo-sensitive high impedance electrode whose impedance can be varied by controlling the light intensity incident on it, is used in a control system for a phased array antenna. Phase is controlled on the Write side of the SLM by controlling the intensity of the Write laser beam which then is accessed by the Read beam from the opposite side of this reflective SLM. Thus the phase of the Read beam is varied by controlling the intensity of the Write beam. A variable fiber-optic delay line is demonstrated in the thesis which uses wavelength sensitive and wavelength insensitive optics to get both analog as well as digital delays. It uses a chirped fiber Bragg grating (FBG), and a 1xN optical switch to achieve multiple time delays. The switch can be implemented using the 3-D optical scanner mentioned earlier. A technique is presented for ultra-low loss laser communication that uses a combination of strong and weak thin lens optics. As opposed to conventional laser communication systems, the Gaussian laser beam is prevented from diverging at the receiving station by using a weak thin lens that places the transmitted beam waist mid-way between a symmetrical transmitter-receiver link design thus saving prime optical power. LC device technology forms an excellent basis to realize such a large aperture weak lens. Using a 1-D array of LC deflectors, a broadband optical add-drop filter (OADF) is proposed for dense wavelength division multiplexing (DWDM) applications. By binary control of the drive signal to the individual LC deflectors in the array, any optical channel can be selectively dropped and added. For demonstration purposes, microelectromechanical systems (MEMS) digital micromirrors have been used to implement the OADF. Several key systems issues such as insertion loss, polarization dependent loss, wavelength resolution and response time are analyzed in detail for comparison with the LC deflector approach. A no-moving-parts axial scanning confocal microscope (ASCM) system is designed and demonstrated using a combination of a large diameter LC lens and a classical microscope objective lens. By electrically controlling the 5 mm diameter LC lens, the 633 nm wavelength focal spot is moved continuously over a 48 [micro]m range with measured 3-dB axial resolution of 3.1 [micro]m using a 0.65 numerical aperture (NA) micro-objective lens. The ASCM is successfully used to image an Indium Phosphide twin square optical waveguide sample with a 10.2 [micro]m waveguide pitch and 2.3 [micro]m height and width. Using fine analog electrical control of the LC lens, a super-fine sub-wavelength axial resolution of 270 nm is demonstrated. The proposed ASCM can be useful in various precision three dimensional imaging and profiling applications.
Ph.D.
Optics and Photonics
Optics

Cette thèse de doctorat traite des métasurfaces constituées de diffuseurs sub-longueur d’onde conçus pour contrôler les fronts d’ondes électromagnétiques. Elle introduit des modèles analytiques et numériques inédits qui résolvent le problème de diffusion inverse en tenant compte des interactions entre éléments de la métasurface. Le manuscrit se concentre plus particulièrement sur des réseaux, périodiques ou non, de fils structurés, permettant la réalisation d’antennes reconfigurables électroniquement. Le manuscrit est divisé en deux grandes parties, l’une sur des arrangements périodiques de fils appelés métaréseaux et l’autre sur des métasurfaces éparses sans caractère périodique. Dans les deux cas, des réalisations expérimentales dans le domaine microondes viennent appuyer les développements théoriques. Dans la première partie, les conditions théoriques conduisant à un contrôle total des ordres de diffraction rayonnés par des métaréseaux, dont la période est composée de plusieurs fils structurés individuellement, sont établies et l’importance du contrôle du champ proche est alors soulignée. Par ailleurs, une expression analytique des paramètres effectifs des fils, s’appuyant sur une simulation numérique, a également été établie. Il devient ainsi possible d’exploiter des géométries quelconques pour des métaréseaux fonctionnant dans les domaines allant des microondes à l’optique. Dans la deuxième partie de la thèse, le modèle analytique des métaréseaux, réservé aux distributions périodiques planes, est généralisé aux distributions non périodiques de fils disposés sur des surfaces quelconques en s’appuyant sur le calcul de la fonction de Green. Ce concept est appliqué à des métasurfaces éparses intervenant dans une cavité Fabry-Perot ou dans une antenne semi-cylindrique. Enfin, la démarche est utilisée pour concevoir une métasurface éparse plane reconfigurable. Un prototype a été réalisé et utilisé pour démontrer expérimentalement le contrôle dynamique de l’onde, en champ lointain et en champ proche, via des applications telles que le dépointage de faisceau, la création de faisceaux multiples ou encore la focalisation au-delà de la limite de diffraction
This PhD thesis deals with electromagnetic metasurfaces for wavefront manipulation represented by arrays of scatterers engineered at subwavelength scale. The manuscript develops novel analytical and numerical models that allow one to solve the inverse scattering problem by taking into account all interactions between elements of a metasurface. Specifically, the manuscript focuses on sparse arrays, periodic or not, of structured wires for the application to electronically reconfigurable antennas. The manuscript is divided into two main parts, one on periodic arrangements of wires called metagratings and one on sparse metasurfaces when there is no periodicity imposed. Each part is endorsed by experiments performed at microwave frequencies. In the first part, theoretical conditions for arbitrary control of the diffraction patterns with metagratings, whose period is composed of multiple individually-engineered wires, are established and importance of the near-field regulation is highlighted. Moreover, an analytical retrieval technique is developed and allows one to consider, with the help of full-wave simulations, arbitrarily structured wires for metagratings operating from microwave to optical domains. In the second part of the thesis, the analytical model of metagratings is generalized, from planar periodic, to arbitrarily-shaped non-periodic distributions of wires by means of numerical calculation of a Green’s function. The concept is applied to design sparse metasurfaces in Fabry-Perot cavity and semi-cylindrical antenna configurations. Finally, the approach is applied to design a reconfigurable planar sparse metasurface. A fabricated sample is exploited to experimentally demonstrate dynamic control of the far-field radiation pattern and the near-field intensity distribution. As such beam-steering, multi-beam manipulation and subdiffraction focusing are shown

The diploma thesis is aimed to design, optimize, produce and subsequently measure the properties of the reflector with the electronic steering direction for the frequency of the 24,125 GHz band ISM. The problem chosen is solved by a group of voltage-controlled varicaps. The reflector consists of a matrix of two rows, each containing 3 cells. The reflector was designed by full-wave software CST Microwave Studio 2015.

The delivery of tunable millimetre-wave components at 60GHz is of research and development interests with the advent of 5G era. Among applications such as high-data-rate wireless communications, high-precision automotive radars and hand-gesture sensing, variable phase shifters are vital components for antenna arrays to steer an electromagnetic beam without mechanical movement. However, present microwave technology has limited scope in meeting more and more stringent requirements in wavefront phase control and device performance for those cutting-edge applications in the millimetre-wavelength range. Although some existing microwave switchable techniques (such as RF MEMS and solid-state p-i-n diodes) can offer ultra-fast speed for phase modulation, their binary beam-steering nature is resolution-limited and thereby degrades the beam-scanning performance. In response to this, continuously-tunable phase shifting can be realised by using tunable dielectric materials such as ferroelectric BST and liquid crystals (LCs). BST thin films can offer relatively fast switching and modest tunability. However, the increased dielectric loss beyond 10GHz impedes their implementation for higher frequency applications. By comparison, liquid crystals (LCs) have drawn attention in recent years because of their continuous tunability as well as low losses especially at millimetre-wavebands. The principle of shifting the phase continuously is based on the shape anisotropy of LC molecules for variable polarizabilities and hence tunable dielectric constants, which allows wave speed to be controlled with ease by a low-frequency field of only up to 10V. However, LC-based tunable delay lines are not well established in the frequency regime of 60GHz-90GHz because of the limited status of LC microwave technology in which most of the LC based devices have been designed for below 40GHz. It is the aim of this PhD research to bridge the gap and address future societal needs based on our group's focus and experience in developing cutting-edge LC-based agile microwave components. In this work, a liquid crystal (LC) based 0-180˚continuously-variable phase shifter is developed with insertion loss less than -4.4dB and return loss below -15dB across a wide spectrum from 54GHz to 67GHz. The device is driven by a 0-10V AC bias and structured in a novel enclosed coplanar waveguide (ECPW) including an enclosed ground plate in the design, which significantly reduces the instability due to floating effects of the transmission line. This structure screens out interference and stray modes, allowing resonance-free quasi-TEM wave propagation up to 90GHz. The tunable ECPW is optimised by competing spatial volume distribution of the millimetre-wave signal occupying lossy tunable dielectrics versus low-loss but non-tunable dielectrics and minimising the total of dielectric volumetric loss and metal surface loss for a fixed phase-tuning range. A variety of influences affecting the actual device performance are studied, experimented and optimised. Fabricated prototypes exhibit wideband low-loss performance and 0-π continuous tuning with low power consumptions and high linearity compared with the state-of-the-arts. Potentially, the ECPW-fed phased antenna array will be incorporated with advanced beam-forming algorithms to develop compact beam-steering systems of improved performances and targeted for ultra-high-data-rate wireless communications, inter-satellite communications, current road safety improvement, futuristic autonomous driving, and other smart devices such as the hand-gesture recognition.

This master thesis deals with a design of Vivaldi antenna due to its broadband properties suitable for radar applications. The folding of single Vivaldi antenna element into 2D antenna array we achieved required radiation properties. Appropriate design of feeding structure realized by SIW technology we obtained suppression of side lobes and deflection of the main lobe. The work also includes design of 3D Vivaldi antenna array. Modeling, simulation and optimization of antenna array were performed in CST Microwave Studio.

博士
國立交通大學
電信工程系所
96
This dissertation deals with novel beam steering techniques and planar reflector antennas. A beam-steering waveguide-fed microstrip antenna array, a dual-mode millimeter-wave folded microstrip reflectarray antenna, a millimeter-wave right-hand circular polarization selective surface, a millimeter-wave three-layered left-hand circular polarization selective surface without any vertical conductive segment and a pattern diversity reflector antenna with minimum number of switching devices have been investigated, designed, built and tested. The theoretical approaches and practical developments of the above five researches are comprehensively discussed. All the simulated results are verified experimentally, and exhibit good consistency with the measured data. The individual subjects are worth further efforts for improvements in the future. Moreover, it is advisable to deploying new applications by combining some of the researches presented in this dissertation.

Dissertação de Mestrado Integrado em Engenharia Electrotécnica e de Computadores apresentada à Faculdade de Ciências e Tecnologia
O tema desta dissertação é a avaliação da performance de técnica fotónicas para beam forming e beam steering no contexto do 5G. Comunicações em ondas milimétricas é atualmente um importante tópico de investigação devido à alta largura de banda disponível que vai permitir elevado trafego necessário paras o 5G e futuras redes. As elevadas perdas e direccionalidade que leva à necessidade de orientar o feixe são os principais desafios nos sistemas de comunicação. Para abranger uma grande área eficientemente vai ser necessária a implementação de beam forming e beam steering nas antenas. Os Phased arrays que são um agregado de antenas que permitem fazer beam forming e beam steering usando atrasos progressivos de phase nos elementos dos agregados. No entanto, os phase shifters de ondas milimétricas sofrem do fenómeno de beam squint que limita a largura de banda de operação. Este problema pode ser resolvido usando um true time delay, este assegura um atraso independente da frequência. A implementação de um true time delay no domínio electrico é de difícil implementação e dispendioso, por isso o domínio ótico torna-se mais interessante para a implementação de um true time delay. Nesta dissertação vai ser desenvolvido um true time delay ótico para substituir os phase shifters elétricos e compensar o fenómeno do beam squint. Vai ser criada uma plataforma de simulação de um sistema de comunicações onde o true time delay ótico vai ser testado, e outros sistemas podem futuramente ser testados. Nesta plataforma de simulação também vamos testar a compensação do beam squint digitalmente no recetor. Com esta tese esperamos obter um método promissor para alcnssar beam forming e beam steering com alta eficiência e baixa complexidade em sistemas de comunicação de ondas milimétricas associados ao 5G.
The topic of this dissertation is the performance evaluation of photonic supported techniques for beam forming and beam steering in the context of 5G. The operation in the Millimeter wave (mmWave) band is currently an important research topic in the communication domain motivated mainly by the amount of available bandwidth that will enable the very high bit rates sought for 5G and beyond 5G communication systems. The blockage effect, propagation loss and high directionality that needs beam alignment are the main challenges for mmWave communication links. To cover a larger area efficiently, the antennas will need to have beam steering and beam forming capabilities. Phased array antennas (PAA) that consists of an array of multiple antenna elements (AEs), enable beam steering that relies on microwave phase shifters which are used to control the phase of each AE. Microwave electrical phase shifters suffer from beam-squint problem which limits the operation bandwidth. Beam quint leads to different frequencies being steered in different directions. This problem can be solved by using true time delay lines (TTDL) which ensures a frequency-independent steering angle. However, TTDL with large bandwidth are difficult to implement in the electronic domain. Conversely, microwave photonics (MWP) where the signal processing is done relying on photonic offers large bandwidth. In this dissertation a simulation platform able to assess the effect of the Beam Squint on the performance of a wireless system was developed. The simulation platform is used to assess performance degradation due to the Beam Squint of extra-high bandwidth mm-wave links that employ Orthogonal Frequency Division Multiplexing (OFDM) signals. We assess the performance of an optical tunable true time delay based on a Macht-Zenher Interferometer (MZI) to replace the electrical phase shifters and decrease the Squint Effect. The simulation platform developed is prepared to test other methods of beam squint compensation for future use. We also explored the possibility of digitally removing the Squint Effect in the receiver.
FCT

Les antennes à pointage électronique présentent des avantages significatifs dans les systèmes de communication sans fil. Malgré cela elles ne sont toujours pas implantées dans l'industrie automobile. En effet, l'espace limité et le toit en grande partie métallique freinent l’utilisation de ces aériens dans ce contexte contraint. De nombreux défis restent à relever pour concevoir un système efficace, peu encombrant, faible coût et permettant de rayonner sur 360°. L’objectif de cette thèse est donc la mise au point d’une antenne à balayage électronique pour application automobile fonctionnant dans la bande LTE. Un système de «type MIMO » est proposé. Une antenne à résonateur diélectrique efficace, multi-bandes et efficace est conçue selon une procédure de développement spécifique. Un déphaseur accordable est également mis au point et réalisé. Il utilise des commutateurs et un condensateur variable. Un déphasage de 360 degrés est obtenu, le dispositif est commandé électriquement. L’antenne et le déphaseur sont ensuite associés dans un système complet fonctionnant dans la bande LTE. Celui-ci utilise deux antennes identiques, une seule étant alimentée. Ce système complet est mesuré seul et sur le véhicule. Les résultats obtenus sont prometteurs et permettent d’envisager, moyennant quelques améliorations, une exploitation industrielle. Les études menées pour aboutir à ce dispositif sont détaillées dans le manuscrit
Even though beam steering technology has significant advantages in wireless communication systems, it is still not implemented in the automotive industry. Indeed, the limited space and the large metal sheet on the rooftop are the challenges for such system. This thesis is focused on the design of the LTE beam steering antenna based on a MIMO system for an automotive environment. An appropriate multiband, efficient and compact Dielectric Resonator Antenna is conceived using a specific development procedure. Also, a tunable phase shifter is designed and realized with switches and a variable capacitor. It has 360 degrees phase shift and can be electrically controlled. The proposed DRA and phase shifter are integrated in a global antenna system for automotive application in the LTE band. We finally propose a MIMO system with an active beam steering radiation pattern. It is very compact and can be implemented on the vehicle rooftop. Using the proposed phase shifter, a beam steering antenna is obtained with a global coverage close to 360� for the antenna alone or on the vehicle. Measurements are made in the using context of the antenna. Finally, the developed system is, with some improvement, powerful for powerful enough for "commercial" automotive applications. The studies carried out to develop this antenna are detailed in this manuscript

M.Ing.
This study considers improving the azimuth beam steering resolution of the circular Switched Parasitic Array (SPA) antennas (made up of dipoles) by a factor of two or more. In circular SPA antennas, beam steering is conventionally achieved by open-circuiting and shortcircuiting different parasitic elements and usually only one parasitic element is open-circuited at a time. However, such an approach results in low beam steering resolutions especially for the SPA antennas with few parasitic elements. In order to increase the azimuth beam steering resolution for the circular SPA antennas, two beam steering methods are proposed in this research work. In the first method, parasitic elements are open-circuited and short-circuited based on different combinations of the parasitic elements and the possible switch states. The proposed method was first validated by simulation tests using the MATLAB tool and WIPL-D. A prototype of the circular SPA antenna consisting of five elements was then implemented. It is noted that the simulation and measurement results match very well at 2.4 GHz. In order to have at least two combinations (from the first method) with almost similar gain and return loss, another simpler beam steering method was developed. The latter method is based on simultaneously open-circuiting either two or three neighbouring parasitic elements. The performance of the second method was studied through simulations using the circular SPA antenna geometries consisting of five, seven and nine elements. These geometries were first optimized (for gain and input impedance) and then modelled using WIPL-D. It was observed that the two methods double the azimuth beam steering resolution of the circular SPA antennas when compared to the conventional beam steering approaches of open-circuiting one parasitic element at a time. Variations in the structural parameters of the five elements circular SPA antenna at 2.4GHz were also investigated. In this procedure, the effects of variations (also considered as random errors) in the structural parameters (or antenna dimensions) on the performance of the SPA antennas were examined. Firstly, variations in each structural parameter were modelled with other structural parameters fixed as per specifications. Thereafter, effects of combined errors were also investigated. The simulation results demonstrated that variations in the structural parameter can either increase or decrease the gain and input impedance of the SPA antenna depending on the given specifications. The gain and input impedance sensitivities per variations in each structural parameter were computed to determine the degree at which the gain and input impedance can vary for a predefined change (error) in the structural parameter.

yes
In this paper, a simple switching process is employed to steer the beam of a vertically polarised circular antenna array. This is a simple method, in which the difference resulting from the induced currents when the radiating/loaded element is connected/disconnected from the ground plane. A time modulated switching process is applied through particle swarm optimisation.
Electronics and Telecommunications

no
Reconfigurable beam steering using circular disc microstrip patch antenna with a ring slotis proposed. The overall dimension of the antenna is 5.4×5.4 mm2 printed on a 0.504 mm thick, Rogers RT5870 substrate with relative permittivity 2.3 and loss tangent 0.0012. The designed antenna operates at the expected 5G frequency band 60 GHz with a central coaxial probe feed. TwoNMOS switches are configured to generate three different beam patterns. Activating each switch individually results in a near 70 degree shift in the main beam direction, whereas the frequency characteristics are unchanged. The power gains are between 3.9 dB and 4.8dB for the three states of switches configurations. Simulated results in terms of return loss, peak gains and radiation pattern are presented and show a reasonable agreement at the expected 60 GHz bandfor 5G applications.
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