Teses / dissertações sobre o tema "Polarization reconfigurable"

A complete all-optical-processing polarization-based binary-logic system, by which any logic gate or processor could be implemented, was proposed. Following the new polarization-based representation, a new Orthoparallel processing technique that allows for the creation of all-optical-processing gates that produce a unique output once in a truth table, was developed. This representation allows for the implementation of all basic 16 logic gates, including the NAND and NOR gates that can be used independently to represent any Boolean expression or function. In addition, the concept of a generalized gate is presented, which opens the door for reconfigurable optical processors and programmable optical logic gates. The gates can be cascaded, where the information is always on the laser beam. The polarization of the beam, and not its intensity, carries the information. The new methodology allows for the creation of multiple-input-multiple-output processors that implement, by itself, any Boolean function, such as specialized or non-specialized microprocessors. The Rail Road (RR) architecture for polarization optical processors (POP) is presented. All the control inputs are applied simultaneously, leading to a single time lag, which leads to a very-fast and glitch-immune POP. A simple and easy-to-follow step-by-step design algorithm is provided for the POP, and design reduction methodologies are discussed. The algorithm lends itself systematically to software programming and computer-assisted design. A completely passive optical switch was also proposed. The switch is used to design completely passive optical gates, including the NAND gate, with their operational speeds only bound by the input beams prorogation delay. The design is used to demonstrate various circuits including the RS latch. Experimental data is reported for the NAND and the Universal gate operating with different functionality. A minute error is recorded in different cases, which can be easily eliminated by a more dedicated manufacturing process. Finally, some field applications are discussed and a comparison between all proposed systems and the current semiconductor devices is conducted based on multiple factors, including, speed, lag, and heat generation.

Els serveis de telecomunicacions i sistemes radar estan migrant a freqüències mil•limètriques (MMW), on es disposa d 'una major amplada de banda i conseqüentment d'una major velocitat de transmissió de dades. Aquesta migració requereix de l'ús de diferents tecnologies amb capacitat d'operar a la banda de freqüències mil•limètriques (30 a 300 Ghz), i més concretament en les bandes Ka (26,5 - 40GHz), V (50 – 75GHz) i W (75 – 110GHz). En moltes aplicacions i sobretot en aquelles on l'antena forma part d'un dispositiu mòbil, es cerca poder utilitzar antenes planes, caracteritzades per tenir unes dimensions reduïdes i un baix cost de fabricació. El conjunt de requeriments es pot resumir en obtenir una antena amb capacitat de reconfigurabilitat i amb un baix nivell de pèrdues en cada una de les bandes de freqüència. Per tal d'afrontar aquests reptes, les dimensions de les antenes mil•limètriques, juntament amb els tipus de materials, toleràncies de fabricació i la capacitat de reconfigurabilitat ens porten a l'ús de processos de microfabricació. L'objectiu d'aquesta tesis doctoral és l'anàlisi dels conceptes mencionats, tipus de materials, geometries de línia de transmissió i interruptors, en el context de les freqüències mil•limètriques, així com la seva aplicació final en dissenys d'antenes compatibles amb els processos de microfabricació. Finalment, com a demostració s'han presentat dissenys específics utilitzables en tres aplicacions a freqüències mil•limètriques: Sistemes de Comunicació per Satèl•lit (SCS) a la banda Ka, Xarxes d'àrea personal inalàmbriques (WPAN) a la banda V i sistemes radar per l'automoció a la banda W. La primera part d'aquesta tesis consisteix en l'anàlisi d'algunes tecnologies circuitals a freqüències mil•limètriques. S'han presentat els materials més utilitzats a altes freqüències (Polytetrafluoroethylene or Teflon (PTFE), Quartz, Benzocyclobuten polymer (BCB) i Low Temperature Co-fired Ceramic (LTCC)) i s'han comparat en termes de permitivitat i tangent de pèrdues. També s'inclou un estudi de pèrdues a altes freqüències en les principals línies de transmissió (microstrip, stripline i CPW). Finalment, es presenta un resum dels interruptors RF-MEMS i es comparen amb els PIN diodes i els FET. En la segona part, es presenten diferents agrupacions d'antenes amb la capacitat de reconfigurar la polarització i la direcció d'apuntament. S'han dissenyat dos elements base reconfigurables en polarització: CPW Patch antena i 4-Qdime antena. La primera antena consisteix en un element singular amb interruptors RF-MEMS, dissenyada per operar a les bandes Ka i V. La segona antena consisteix en una arquitectura composta on la reconfigurabilitat en polarització s'obté mitjançant variant la fase d'alimentació de cada un dels quatre elements lineals. La fase és controlada mitjançant interruptors RF-MEMS ubicats en la xarxa de distribució. L'antena 4-Qdime s'ha dissenyat per operar en les bandes V i W. Ambdós elements base s'han utilitzat posteriorment pel disseny de dues agrupacions d'antenes amb capacitat de reconfigurar l'apuntament del feix principal. La reconfigurabilitat es dur a terme utilitzant desfasadors de fase d'1 bit. La part final de la tesis es centra en les toleràncies de fabricació i en els processo de microfabricació d'agrupacions d'antenes mil•limètriques. Les toleràncies de fabricació s'han estudiat en funció dels error d'amplitud i fase en cada element de l'agrupació, fixant-se en les pèrdues de guany, error d'apuntament, error en l'amplada de feix, errors en el nivell de lòbul secundari i en l'error en la relació axial. El procés de microfabricació de les diferents antenes dissenyades es presenta en detall. Els dissenys de l'antena CPW Patch reconfigurable en polarització i apuntament operant a les bandes Ka i V, s'han fabricat en la sala blanca del Cornell NanoScale Science & Technology Facility (CNF). Posteriorment, s'han caracteritzat l'aïllament i el temps de resposta dels interruptors RF-MEMS, i finalment, el coeficient de reflexió, el diagrama de radiació i la relació axial s'han mesurat a les bandes Ka i V per les antenes configurades en polarització lineal (LP) i circular (CP).
Telecommunication services and radar systems are migrating to Millimeter-wave (MMW) frequencies, where wider bandwidths are available. Such migration requires the use of different technologies with the capability to operate at the MMW frequency band (30 to 300GHz), and more specifically at Ka- (26.5 to 40GHz), V- (50 to 75GHz) and W-band (75 to 110GHz). For many applications and more concretely those where the antenna is part of a mobile device, it is targeted the use of planar antennas for their low profile and low fabrication cost. A wide variety of requirements is translated into a reconfiguration capability and low losses within each application frequency bandwidth. To deal with the mentioned challenges, the MMW antenna dimensions, together with the materials, fabrication tolerances and reconfigurability capability lead to microfabrication processes. The aim of this thesis is the analysis of the mentioned concepts, materials, transmission lines geometries and switches in the MMW frequencies context and their final application in antenna designs compatible with microfabrication. Finally, specific designs are presented as a demonstration for three MMW applications: Satellite Communication Systems (SCS) at Ka-band, Wireless Personal Area Network (WPAN) at V-band and Automotive Radar at W-band. The first part of this thesis consist to analyze some MMW circuit technologies. The four most used materials at MMW frequencies (Polytetrafluoroethylene or Teflon (PTFE), Quartz, Benzocyclobuten polymer (BCB) and Low Temperature Co-fired Ceramic (LTCC)) have been presented and compared in terms of permittivity (εr) and loss tangent (tanδ). An study of the main transmission lines attenuation (microstrip, stripline and CPW) at high frequencies is included. Finally, an overview of the RF-MEMS switches is presented in comparison with PIN diodes and FETS switches. The second part presents different polarization and beam pointing reconfigurable array antennas. Two polarization-reconfigurable base-elements have been designed: CPW Patch antenna and 4-Qdime antenna. The first consists of a single reconfigurable element with integrated RF-MEMS switches, designed to operate at Ka- and V-band. The second antenna presented in this thesis has a composed architecture where the polarization reconfigurability is obtained by switching the phase feeding for each of the four linear polarized elements in the feed network with RF-MEMS switches. The 4-Qdime antenna has been designed to operate at V- and W-band. The two base-elements have been used to design two beam pointing reconfigurable antenna arrays. Using phased array techniques, beamsteering is computed and implemented with 1-bit discrete phase-shifter. The final part of the thesis is focused into the fabrication tolerances and microfabrication process of Millimeter-wave antenna arrays. The fabrication tolerances have been studied as a function of the amplitude and phase errors presented at each elements array, focusing on the gain loss, beam pointing error, Half-Power Beamwidth (HPBW) error, sidelobe level error and axial ratio error. The microfabrication process for the designed antennas is presented in detail. Polarization- and pointing- reconfigurable CPW Patch antenna operating at Ka- and V- band have been fabricated in a clean-room facility at Cornell NanoScale Science & Technology Facility (CNF). The RF-MEMS switches isolation and time response have been characterized. Finally, the reflection coefficient, radiation pattern and axial ratio have been measured at Ka- and V-band for the fabricated antennas configured in Linear Polarization (LP) and Circular Polarization (CP).

Thesis (Ph.D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.
Committee Chair: Manos M. Tentzeris; Committee Co-Chair: John Papapolymerou; Committee Member: Andrew F. Peterson; Committee Member: Chang-Ho Lee; Committee Member: John D. Cressler; Committee Member: Joy Laskar.

This Thesis investigates and develops novel bidirectional and reconfigurable optical access architectures based on WDM technology with the aim of solving the problem of cost and complexity associated to the WDM-PON transceivers. In particular, depending on the capacity requirements of the network, the investigation and development deal with two specific environments of application. In case of low capacity access platforms, we propose and validate new dispersion tolerant optical transmission systems based on the employment of optical broadband sources operating in the third transmission band and whose adaptability to the transport of RoF signals is realized, for the first time, by means of Mach-Zehnder optical interferometer structures. The optical bandpass filtering feature of the Mach-Zehnder device is key to overcome the chromatic dispersion-induced limitations arising from the spectral width of the source and, thus, significantly increase the system operative bandwidth to several tens of GHz. The incorporation of a Mach-Zehnder structure has a relatively low degree of implementation complexity and opens the possibility to transmit RoF signals using cost-effective optical broadband sources in optical access platforms being, at the same time, a viable alternative to other dispersion compensation techniques under certain scenarios. Good RoF transmission performance is experimentally achieved over single mode and multi mode fiber links employing optical amplitude and optical phase modulation. The SCM technique is also used for the generation of down- and up-stream signals to improve the link bandwidth utilization and allow converging transport of wired and wireless services. Service flexibility is demonstrated by means of different types of codification concerning the transmitted binary information. In spectrum sliced optical broadband source multichannel applications, the dynamical assignment of capacity is realized by means of a compact routing scheme based on optical switching and validated over different routing scenarios. Moreover, two extra functionalities offered by the Mach-Zehnder device, such as the photonic suppression of harmonic and intermodulation distortion and the all-optical microwaves generation and up-conversion, are demonstrated. For optical access platforms requiring high capacity transport we propose and validate light sources-centralized optical transmission systems where the PolMUX technique is employed for the first time in the access platform as a novel strategy to minimize the cost and complexity of the terminal units in accordance with the centralization concept. The PolMUX principle uses light polarization as a degree of freedom to efficiently multiplex two orthogonal optical fields at the same wavelength into the same optical channel. Under this principle, the optical carriers required for the down- and uplink transmission can be provided by a single and centralized coherent source. It means that the terminal unit can be kept source-free and operative wavelength-independent. This concept is firstly validated over a single-channel full-duplex optical transmission system adopting RoF and SCM techniques for the generation and transport of the down- and upstream signals. Apart of fulfilling the requirements of quality of transmission after the polarization demultiplexing process, we demonstrate that the tracking and control of polarization can be also centralized at the central office for further minimization of the terminal unit complexity. Finally, the effectiveness of the PolMUX technique is exploited in the access network in order to perform full-duplex multichannel communications where reconfiguration of capacity depending on the actual demand and service convergence, required in RoF, are also demonstrated.
Grassi Marangione, F. (2013). Centralized transmission techniques for full-duplex reconfigurable WDM optical access networks [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/34507
TESIS

Recently, reconfigurable antennas have attracted significant interest due to their high adaptation with changing system requirements and environmental conditions. Reconfigurable antennas have the ability to change their radiation pattern, frequency or polarization independently according to the application requirements. In this thesis, three different reconfigurable antenna structures have been designed
beam-steerable meanderline antenna, dual circularly polarized meanderline antenna and dual-frequency slot-dipole array. Traveling wave meanderline antenna arrays are investigated in detail and a beam-steerable traveling wave meanderline antenna array has been introduced for X-band applications. Beam-steering capability of the antenna array has been achieved by loading the antenna elements with varactor diodes. Theoretical analysis and computer simulations of the proposed antenna have been verified with experimental results. Radiation direction of the 8-element meanderline array can be rotated 10°
by changing the varactor diode&rsquo
s bias voltage from 0V up to 20V. Also, a polarization-agile meanderline antenna array has been designed and simulated. Polarization of the circularly polarized meanderline array can be altered between right hand circularly polarized and left hand circularly polarized by using RF MEMS switches. The third type of reconfigurable antenna investigated in this thesis is a dual frequency slot-dipole array operating at X- and Ka-band. Electrical length of the slot dipoles has been tuned by using RF MEMS switches. Antenna prototypes have been manufactured for &lsquo
on&rsquo
and &lsquo
off&rsquo
states of RF MEMS switches and it has been shown that the operating frequency can be changed between 10 GHz and 15.4 GHz.

La croissance rapide des applications de l’Internet des objets (IoT) a entrainé une forte demande en technologies sans fil avancées. Dans le contexte d’un paysage numérique en constante évolution, les antennes reconfigurables sont devenues un point focal crucial en raison de leur nature adaptable. Ce travail offre un aperçu complet du paysage actuel des technologies IoT et sans fil, en mettant l’accent sur les normes compatibles avec l’IoT et la manière dont elles ont influencé la conception des antennes. Cette recherche explore les défis de la conception, de l’optimisation et de la mise en œuvre de ces antennes spécifiquement pour les réseaux IoT modernes. Les principes fondamentaux des antennes miniatures électriquement petites (ESA) et des conceptions d’antennes reconfigurables pour les applications IoT constituent la base de ce travail. Tout d’abord, l’exploration d’une antenne à polarisation circulaire omnidirectionnelle (OCP) miniature est effectuée, et une analyse approfondie de ses paramètres d’optimisation et de sa polarisation circulaire est réalisée. Une étude sur l’antenne OCP reconfigurable est également fournie, avec un accent sur les stratégies de mise en œuvre pratique. En outre, la recherche explore la reconfigurabilité du diagramme, une caractéristique qui permet à l’antenne de modifier dynamiquement son diagramme de rayonnement. Une antenne à réseau parasitaire orientable électroniquement (ESPAR) reconfigurable et à profil bas est conçu et optimisé, avec présentation et analyse des résultats mesurés. La recherche propose également des solutions potentielles au problème de réoptimisation associé à la mise en œuvre pratique des circuits de commutation. L’étude inclut également des tests sur le terrain en conditions réelles. La conception et les essais sur le terrain d’une antenne ESPAR pour les applications IoT à longue portée basées sur les véhicules aériens sans pilote (UAV) sont discutés, en couvrant l’intégration du transceiver. Enfin, ce travail aborde la conception d’une antenne reconfigurable en fréquence pour les communications IoT basées sur les satellites, avec les défis de la miniaturisation et de la reconfigurabilité au premier plan
The rapid growth of Internet of Things (IoT) applications has led to a surge in demand for advanced wireless technologies.In the context of an ever-evolving digital landscape, reconfigurable antennas have emerged as a pivotal focus due to their adaptive nature.This work provides a comprehensive overview of the current landscape of IoT and wireless technologies, with a focus on the IoT-compliant standards and how they have influenced antenna design. This research explores the challenges of designing, optimizing, and implementing these antennas specifically for modern IoT networks. The fundamental principles of miniature Electrically Small Antennas (ESA)s and reconfigurable antennas designs for IoT applications builds the foundation of this work.Firstly, the exploration of a miniature Omnidirectional Circular Polarization (OCP) antenna, and an in-depth analysis of its optimization parameters and circular polarization is carried out. A study on reconfigurable OCP antenna is also provided, with a stress on practical implementation strategies. Further, the research explores pattern reconfigurability, a feature that allows the antenna to dynamically alter its radiation pattern. A low-profile Pattern Reconfigurable Electronically Steerable Parasitic Array Radiator (ESPAR) is designed and optimized, with measured results presented and analyzed. The research also proposes potential solutions to the re-optimization problem associated with the practical implementation of switching circuits. The study also includes real-life field-testing. The design and on-field testing of an ESPAR antenna for Unmanned Aerial Vehicle (UAV) based long-range IoT applications are thus discussed, covering the integration of the transceiver. Finally, this work discusses the design of a frequency reconfigurable antenna for satellite-based IoT communications, with the challenges of miniaturization and reconfigurability at the forefront

Gli obiettivi di questo studio sono l'ideazione e il progetto di componenti a microonde innovativi, destinati in particolare alle applicazioni satellitari. Due sfide che i progettisti di queste architetture si trovano attualmente ad affrontare sono la necessità di ridurre peso e volume dei satelliti, e l'introduzione della capacità di riconfigurazione. Entrambi i requisiti puntano alla riduzione dei costi dei payload, e all'estensione della loro vita, intesa come intervallo di tempo durante il quale il payload rimane operativo. Il primo argomento discusso in questa tesi è il progetto di una classe di accoppiatori direzionali a microonde, che permetta la riduzione del peso del satellite fondendo le due reti di beam-forming che alimentano le due polarizzazioni ortogonali delle antenne in una singola struttura sovramodata. Questa classe di componenti è nota in letteratura come a "doppia polarizzazione". Degli accoppiatori a quattro-porte che supportano due polarizzazioni furono già introdotti nel 1997. In questo lavoro, vengono definite delle linee guida di progetto per questi componenti, basato sulla scelta ponderata del tipo di elementi di accoppiamento al fine di garantire un elevato accoppiamento, mantenendo l'isolamento tra le polarizzazioni ortogonali. Al momento della stesura di questo lavoro non sono reperibili, sia nella letteratura internazionale che nelle banche dati dei brevetti, esempi di accoppiatori direzionali a doppia polarizzazione con un numero di porte superiore a quattro. In questa tesi, viene descritto un accoppiatore direzionale a 6 porte, che supporta la doppia polarizzazione. Questo componente innovativo è stato inizialmente progettato con un simulatore elettromagnetico commerciale, ed in seguito ne è stato realizzato un prototipo con il quale sono stati verificati i risultati ottenuti. La seconda parte di questo studio riguarda dei diplexer riconfigurabili, dove la frequenza centrale dei canali può essere posizionata in modo arbitrario, fino al caso limite di canali contigui. Viene descritto e migliorato un prototipo circuitale di diplexer riconfigurabile basato sul concetto di 'dual-manifold' proposto da J. D. Rhodes. Inoltre, tale prototipo circuitale è stato adattato ad una realizzazione fisica in guida d'onda, appropriata per le applicazioni spaziali. Il progetto di questo componente ha richiesto l'introduzione di filtri composti di cavità sovramodate, in particolare cavità cilindriche operanti con il modo TE011, al fine di garantire basse perdite di potenza. Il progetto efficiente di tali strutture si è rivelato un compito impegnativo. Pertanto, questo studio comprende anche la descrizione di una tecnica innovativa per la segmentazione di filtri composti da cavità sovramodate, che può essere impiegata per predire in modo efficiente la risposta finale del filtro, riducendo la complessità delle simulazioni elettromagnetiche richieste. In tal modo, il progetto di queste strutture complesse risulta un compito più semplice.
The aim of this study is the ideation and design of innovative microwave components, particularly suited for satellite applications. Two actual challenges in the design of architectures for this kind of applications are the need to reduce the overall mass of the satellites, and the introduction of reconfigurable capabilities. Both the requirements aim to reduce the costs of the payload, and to extend its lifetime, that is the interval of time the payload remains operative. The first topic covered by this thesis is the design of a class of microwave passive directional couplers, that allows for the reduction of the mass of a satellite by fusing the two beam forming networks feeding each polarization of the double-polarization antennas into a single overmoded structure. This class of components has been referred as "dual-polarization" in the literature. Four-port directional couplers supporting two polarizations were already introduced in 1997. Here, the design guidelines of a dual-polarization directional couplers are defined. The design is based on a judicious choice of the coupling elements in order to guarantee acceptably large coupling and high isolation between orthogonal polarizations. Then, the case of a 6-port directional couplers is considered. No examples of dual-polarization directional couplers with more than 4 ports have been reported so far, both in the international literature and in the patent repositories. In this thesis a 6-port directional coupler working in double polarization is described. The novel component has been designed with commercial full-wave electromagnetical solver, and a prototype has been manufactured and tested. The second topic concerns diplexers whose channel centre frequencies can be arbitrarily positioned, resulting in contiguous and non-contiguous channel spacing. A circuit prototype of tunable diplexers based on the ‘dual-manifold’ concept, proposed by J.D.Rhodes, has been considered and improved. Moreover, the circuital prototype has been adapted to a physical realization in waveguide, suitable for space applications. The design of this component required the introduction of filters made of overmoded cavities, such as circular cavities operating in the TE011 mode, to guarantee low power losses. The efficient design of such structures is a challenging task. Therefore, this study also comprehends the description of a novel technique to segment a filter made of overmoded cylindrical cavities, that can be used to efficiently predict the overall response of the filter. The method reduces the complexity of the full-wave electromagnetic simulation to be performed, thus making easier the design of these complex structures.

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

La demande croissante des réseaux optiques actuels en termes de bande passante résulte en un besoin d'exploiter la capacité offerte par la fibre optique. Un des moyens indispensable pour permettre ceci est l'utilisation du multiplexage en longueur d'onde. Il en résulte la nécessité d'utilisation de dispositifs, parmi lesquels le filtre optique, agiles en longueur d'onde et transparents par rapport aux débits. C'est dans ce contexte que notre travail se situe. La technologie utilisée est celle des filtres interférentiels en polarisation. Contraint par un cahier des charges particulier aux applications télécoms, le principal objectif consiste en l'augmentation des performances de ce type de filtre d'une part, et l'association de fonctionnalités additionnelles nécessaires dans les réseaux d'autre part. En utilisant le principe physique des interférences en polarisation, une structure est alors implémentée, suivant les contraintes liées aux trois paramètres majeurs du filtre que sont le contraste, la fonction d'égalisation et la reconfiguration de la bande passante. Par ailleurs, les architectures des filtres optiques diffèrent selon l'emplacement dans le réseau. Ainsi, si une architecture des plus simples est utilisée à la réception, au niveau des nœuds du réseau, celle-ci devient beaucoup plus complexe, s'adaptant à différents degrés de nœuds, et portent le nom de multiplexeurs optiques à insertion/extraction de longueur d'onde (ROADM). Un dispositif de ce type, basé sur les filtres biréfringents, est donc présenté. Une approche système est ensuite menée dans le but de mettre en évidence les avantages et les limitations de la technologie utilisée

Dans les systèmes de communication et de détection sans fil, l'antenne est un élément indispensable pour transformer l'énergie électrique en ondes électromagnétiques rayonnée dans l'espace, et vice versa. Les antennes sont utilisées dans de nombreux dispositifs militaires et civils, tels que les radars (SAR, secteur automobile, détection de débris, etc.), les instruments biomédicaux, les systèmes de télécommunication (téléphones mobiles, stations de base) pour les communications point à multi-point ou point à point par exemple. Les antennes jouent aussi un rôle essentiel pour le développement de futurs réseaux connectés reliant plusieurs appareils à des utilisateurs en temps réel, par exemple pour l'Internet des objets (IoT). Les réseaux transmetteurs sont une solution attrayante pour de nombreuses applications telles que les communications par satellite (Satcom) ou les futurs réseaux 5G. L'architecture des antennes à réseau transmetteur les rend extrêmement compétitifs comparés aux réseaux phasés par exemple grâce à leur alimentation par onde d’espace et car ils ne souffrent pas du blocage induit par la source primaire, comme c’est le cas pour les réseaux réflecteurs ou les antennes à réflecteur. Grâce à leur fonctionnement en mode transmission, les réseaux transmetteurs peuvent être également facilement montés sur des plates-formes mobiles.Les applications Satcom en bande Ka constituent le secteur applicatif majeur de cette thèse. Cette bande fournit un débit de données élevé à la fois pour les liaisons descendantes et les liaisons montantes, en remplacement des systèmes actuels en bande Ku. Dans ce contexte, il convient aussi de prêter une attention particulière aux communications avec des plates-formes mobiles, par exemple les trains à grande vitesse, les avions, etc., ce qui nécessite de mettre au point des antennes à balayage de faisceau. De nombreuses propriétés avancées sont exploitées depuis ces dernières années pour accroître les débits et la flexibilité des systèmes de communication sans fil, par exemple la polarisation circulaire, la double polarisation, le fonctionnement multi-fréquence ou large bande, le dépointage électronique de faisceau. Pour réduire les coûts, des preuves de concept de réseaux transmetteurs non diélectriques sont également proposées. Cette thèse s’est déroulée dans le cadre du projet ANR TRANSMIL (Reconfigurable TRANSmitarrays for beam steering and beam forming at MILlimetre wave). Les objectifs de cette thèse sont de proposer de nouvelles architectures de réseaux transmetteurs fonctionnant en bande Ka en liaison descendante (de 17,7 GHz à 21,2 GHz) et en liaison montante (de 27,5 GHz à 31 GHz). Différents prototypes ont été conçus et fabriqués afin de valider les concepts proposés en bande X et en bande Ka. Un bon accord entre les résultats numériques et mesurés a été obtenu systématiquement. En particulier, les réseaux transmetteurs à double polarisation que nous avons conçus en bande X présentent un gain de 25 dBi et une bande passante à 3 dB de 20% à 10 GHz. Ces propriétés sont indépendantes de la polarisation du champ rayonné, ce qui signifie que des faisceaux de polarisation linéaire orthogonale peuvent être rayonnés indépendamment dans des directions différentes. Un réseau transmetteur bi-bande fonctionnant en bande Ka a également été mis au point. Sa bande passante à 3 dB est de 10% autour des fréquences centrales (19,5 GHz et 29 GHz) et son efficacité de rayonnement atteint 60%. D’autres concepts ont également été étudiés (réseaux transmetteurs sans diélectrique, réseau transmetteur reconfigurable)
Transmitarray is an attractive solution for front-end devices in the next generation of communications (5G). The spatial-fed architecture of transmitarray antennas can compete with phase-arrays due to the absence of feeding network and with reflectarrays since they do not suffer from feed blockage. Thanks to their operation in transmission mode, transmitarrays can be easily mounted on platforms for outdoor environment applications. With mature printed-circuit board technology, there are unstoppable experiments in various frequency bands from cm-wave to mm-wave and up to terahertz in upcoming years for potential applications. Many advanced properties are exploited in transmitarrays in recent years to meet high demands of communications facilities, for example, circular-polarization, dual-/multi-polarization or frequencies through many techniques. Some experiments are consid-ered to validate eligibility of this antenna type in commercial services or military missions, namely electronically steering beam, broad bandwidth, etc. In terms of cost reduction and rigidity, non-dielectric prototypes are also proposed. The Ka-band Satcom applications are the main objective of this thesis through trans-mitarray solution. This band provides high data rate for both down-link and up-link in replacement of the current Ku-band systems with miniaturized module in next dec-ades. Hence, it is worth to pay attention to communications for moving platforms, for example, high-speed trains, planes, etc

碩士
逢甲大學
電機工程學系
103
This thesis focuses on polarization reconfigurable antenna research, and two polarization reconfigurable antennas with different feeding mechanisms are proposed. The initial design of first proposed antenna (antenna 1) is a rectangular-shaped ground plane (50 × 60 × 0.8 mm3) loaded with a ring-shape slot. By applying the microstrip line feeding technique, a linearly polarized radiation (TM11 mode) can be excited. In order to generate circularly polarization (CP) radiation, two meandered narrow slots of quarter-wavelength long are loaded symmetrically below the ring-shape slot at ± 23° along the negative Y-axis. By switching the two PIN diodes embedded into the meandered narrow slots, the proposed antenna 1 can switch between left hand circular polarization (LHCP), right hand circular polarization (RHCP), and linear polarization (LP). The second proposed antenna (antenna 2) is a coplanar waveguide (CPW)-fed polarization reconfigurable antenna. By switching the two PIN diodes embedded between T-shape feeding line and open square-loop radiating element, the proposed antenna 2 can also switch between LHCP, RHCP, and LP. Because both the RF and DC signals must be fed from the same feeding line (input port), therefore, during the experiment, an additional Bias-Tee element must be connected to the input port for combining the two signals. The two proposed antennas have the advantages such as low-profile, simple structure, and require only a pair of PIN diodes to switch between three polarizations. By comparing the two antennas design, even though proposed antenna 2 has exhibited wider CP bandwidth and smaller size (50 × 53 × 0.8 mm3) over proposed antenna 1, it requires a much complicated bias-network. Nonetheless, the two proposed antennas when operating within the three polarizations are able to cover the WLAN 2.4 GHz applications. Keywords―Reconfigurable antenna, polarization reconfiguration, circular polarization, pin diode

碩士
正修科技大學
電子工程研究所
99
In this paper, patch antennas with reconfigurable polarization are presented. The designs use feed mechanism and bias control to alter the polarization. The first design is an L-strip-fed patch antenna. The horizontal and vertical portions of L-strip coupling feed two radiation elements, respectively. It can provide a pair of orthogonal E-fields. Also, the feeding mechanism can adjust impedance matching and suitable phase difference to achieve a RHCP condition. Besides, changing the location of horizontal and vertical portions of L-strip can achieve LHCP easily. Secondly, the design is a T-Strip-fed patch antenna with reconfigurable polarization. It uses T-strip coupling feed two radiation elements to achieve a LP condition. In addition, the antenna can change polarization from LP to LHCP or RHCP conditions by bending the antenna. The antenna does not use another element to change polarization. Lastly, the design is a patch antenna with a varactor. This antenna uses an impedance matching coupling a radiation element to provide a pair of orthogonal E-fields. Besides, we put a varactor on feeding network and use bias to tune the varactor to provide a 90 phase. Then, we can achieve a CP radiation.

碩士
國立中正大學
電機工程所
96
This thesis focuses on design of the polarization-reconfigurable antenna system. The polarization of the antenna is determined by its configuration and feeding technique. Due to the surrounding environment and multi-path effect, the receiver antenna may not have the same polarization with the signal polarization, which will degrade the communication quality. Due to this reason, there is an urgent need to design an antenna system with polarization-reconfigurable capability so that it can adaptively receive the signals in all kinds of communication conditions. In this research work, two feeding circuits are designed to provide the antenna with switchable RHCP, LHCP and LP polarizations. The first feeding circuit is designed at 2.4 GHz on printed-circuit board. The circuit consists of one Wilkinson power divider, four SPST switches and two enhanced 90° Schiffman phase shifters. By controlling the switches, the signal path can be selected. This feeding circuit is also integrated with a dual-feed circular patch antenna for demonstration. The measurement results shows the operation bandwidth is 1.6 GHz to 2.7 GHz within AR<3. The second feeding circuit is implemented by standard 0.18-μm CMOS technology. With different approach, this circuit consists of one transformer-based 3-dB quadrature coupler and a SPDT three-mode switch. To remain the good impedance match during switching, the circuit also includes the impedance –reconfigurable mechanism. This circuit is designed at 10 GHz with very compact chip size of (0.65x1.06 mm2)

碩士
國立交通大學
電信工程系所
94
This thesis is devoted in design of the reconfigurable planner microstrip aperture coupled quadri-polarized antenna. Nowadays, the polarization diversity is more and more attracted in communication system. It is effective to counter the fading loss caused by multi-path effects and double the channel capacities. Also, polarization diversity increases the SNR and performance of the communication systems greatly. The polarization diversity is applied in WLAN、RFID and mobile communication that prove it is very important in communication systems. Majority of the polarized antennas own dual-polarization characteristics but few polarized antennas can provide four polarization senses. In this thesis, three planar reconfigurable quadri-polarization microstrip aperture-coupled patch antennas are proposed. They can switch the different polarization scenes by controlling the pin-diodes embedded in the feeding network.

碩士
國立交通大學
電信工程研究所
98
A novel multiple-ear patch antenna for polarization and frequency diversities is proposed. The proposed antenna uses the PIN diodes and adjacent ears, which are small adjacent patches, to achieve the diversities purposes. By connecting or disconnecting the ears and main patch, both of the resonant frequency and transverse magnetic (TM) of proposed antenna are changed to achieve the diversities. The proposed antenna has a compact size and simple structure, which comprises of a main patch antenna, four adjacent patches and four PIN diodes. With suitable arrangement of the bias network, the proposed antenna demonstrates either switching frequency in 3.2, 3.35 or 3.6GHz with the linear polarization (LP); or switching polarization in linear, right hand circular or left hand circular polarization (RHCP/ LHCP) in the same frequency. The simulated and measured results reveal good impedance bandwidth, axial ratio, and radiation patterns; hence the proposed reconfigurable mechanism is well suited for wireless communication applications.

碩士
國立彰化師範大學
電機工程學系
96
A three-element circularly-polarized (CP) slot antenna composed of a circular wide slot, a director patch, and a metallic reflector is first studied in this thesis. The CP radiation of the slot antenna is excited by the proximity coupling of an L-shaped strip. To obtain an optimum peak gain and a broad CP bandwidth, the effects of varying the positions of the director and reflector on the antenna performances are respectively investigated. Then, the three-element CP slot antenna structure is used to design a reconfigurable antenna whose polarization can be adjusted by mechanically rotating a conducting strip. A prototype of the reconfigurable antenna was implemented and measured. Experimental results exhibit that the prototype can provide one linear polarization and dual circular polarization operations over a 10dB-return-loss impedance bandwidth of 21 %; moreover, the antenna gain is around 10 dBi for each polarization operation. Finally, a grounded ring slot antenna with CP operation is studied to reduce back radiation, and it is used as the elements of polarization reconfigurable arrays with a series-fed network. The polarization switching of the arrays is achieved by controlling the states of diodes. Details of the array designs are described. Keywords: slot antenna, broadband, high gain, polarization switching, array

Yes
This paper presented a new circular polarization reconfigurable antenna for 5G wireless communications. The antenna, containing a semicircular slot, was compact in size and had a good axial ratio and frequency response. Two PIN diode switches controlled the reconfiguration for both the right-hand and left-hand circular polarization. Reconfigurable orthogonal polarizations were achieved by changing the states of the two PIN diode switches, and the reflection coefficient |S11| was maintained, which is a strong benefit of this design. The proposed polarization-reconfigurable antenna was modeled using the Computer Simulation Technology (CST) software. It had a 3.4 GHz resonance frequency in both states of reconfiguration, with a good axial ratio below 1.8 dB, and good gain of 4.8 dBic for both modes of operation. The proposed microstrip antenna was fabricated on an FR-4 substrate with a loss tangent of 0.02, and relative dielectric constant of 4.3. The radiating layer had a maximum size of 18.3 18.3 mm2, with 50 W coaxial probe feeding.
European Union’s Horizon 2020 research and innovation programme under grant agreement H2020-MSCA-ITN-2016 SECRET-722424.

碩士
國立中正大學
電機工程所
98
A design of polarization reconfigurable antenna feeding network is proposed in this work, it contains two parts. The first part describes a reconfigurable multi-phase power divider with variable output power ratio and multiple output phases, which is composed by CPW-G coupler, reflection load and switchable phase sifter. When the circuit connects to a patch antenna with orthogonal input port, it will synthesize linear polarization, left-handed circular polarization, right-handed circular polarization and right/left-handed ellipse polarization with different axial ratios, enabling the antenna system to receive signal in any environments by many polarization modes effectively. Meanwhile, this work uses the circuit property to realize an automatic antenna polarization measurement system by LabVIEW software. Second part designs two 0.18 μm CMOS reconfigurable power dividers, the operation frequencies are at 24 GHz and 60 GHz. The 24 GHz reconfigurable power divider contains 90° Couplers and tunable loads. The 60 GHz Circuit contains 90° Couplers and tunable phase shifters, it has variable output power ratio and in-phase or out-of-phase mode by tuning the phase difference of the phase shifters. The characteristics of these circuits could increase the applications of millimeterwave chip antenna systems widely.

碩士
國立臺北科技大學
電子工程系研究所
105
This thesis presents a reconfigurable antenna based on a circular patch antenna with diode switches. By turning on or off the diode switches, the polarization of the antenna can be changed, such that a single antenna can receive incoming signals of different polarizations. The change of diode switch states can also change operating frequencies. We hope that these operating frequencies can cover from 700 MHz to 3 GHz, satisfying major mobile communication frequency bands and providing future expanse of more frequency bands. The structure of the antenna is based on a circular patch antenna with a ring slot on it. On the ring slot, a total of 24 diodes are placed at an equal interval of 15°. A 0.2-mm wide slit is added on the circular patch from the ring slot to the outer edge at a 15° interval, so that the circular patch is equally divided into 24 blocks. By using circuit theory, a Matlab program is employed to simulate all combination of diode states to find the highest return loss value at each frequency and the corresponding diode configuration. Finally, even though the proposed antenna does not meet the bandwidth goal, it still satisfies part of the bandwidth.

碩士
國立彰化師範大學
電機工程學系
106
Two designs for antennas with quad-polarization diversity is described in in this thesis. For the first one, the antenna structure is mainly composed of a reconfigurable crossed dipole fed with coaxial baluns and a switchable feeding network. By controlling the states of pin diodes embedded in the balun feeds, the crossed dipole can generate vertical and horizontal polarization radiations, and the phase of each polarization mode can be switched between 0° and 180°. As for the feeding network, it has four output ports and only two output ports are set to be active to excite the crossed dipole at a time. By integrating the crossed dipole with the feeding network, the resultant antenna can provide four polarization modes, including ±45° linear polarizations and dual orthogonal circular polarizations. Moreover, the overlapped operation bandwidth of the four polarization modes is more than 35 %, and within the bandwidth, the cross polarization level of the linear polarization modes is less than −20 dB and the axial ratio of the circular polarization modes is smaller than 3 dB. Good impedance matching is also achieved for each polarization mode. For the second design, its design concept is similar to that of the first one, but a metallic box is adopted as the reflector of a crossed dipole. With metallic box, the operation bandwidth of the antenna with quad-polarization diversity is increased from 35 % to 50 %; besides, the beamwidths of the antenna in the E and H planes are almost the same, leading to a wide circular polarization beamwidth. The measured results show that the antenna operating in the four polarization modes has good performances, and an average gain of about 4.3 dBi(c) is obtained within the frequency band from 1.6 to 2.6 GHz.

Yes
This paper presents a circular polarization reconfigurable antenna for 5G applications, which is compact in size and has good axial ratio and frequency response. The proposed microstrip antenna is designed on a FR-4 substrate with a relative dielectric constant of 4.3 and has a maximum size of 30×30 mm2 with 50 Ω coaxial probe feeding. This design has two PIN diode switches controlling reconfiguration between right hand circular polarization (RHCP) and left hand circular polarization (LHCP). To achieve reconfigurability, a C-slot rectangular patch antenna with truncated corner techniques is employed by cutting off two corners on the radiating patch. The proposed antenna has been simulated using CST microwave studio software: it has 3.35-3.77 GHz and 3.4-3.72 GHz bands for both states of reconfiguration, and each is suitable for 5G applications with a good axial ratio of less than 1.8 dB and good gain of 4.8 dB for both modes of operation.
Innovation programme under grant agreement H2020-MSCA-ITN-2016 SECRET-722424, UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1.

The objective of work is to design and develop Polarization Reconfigurable Micro strip patch antenna which radiate electromagnetic wave of various orthogonal patterns. A progression of parametric study was done to get that how the features of the antenna depends on dimensions and material of geometry. Simulation of antenna has to be done by using CST microwave studio and HFSS. Antennas of various geometry have to be simulated and fabricated which radiates various orthogonal patterns of electromagnetic wave. The first antenna is to design and develop dual feed reconfigurable circularly polarized microstrip patch antenna feeding with microstrip line. By using switch and two feedline antenna is capable to radiate RHCP and LHCP. The second antenna is to design and develop reconfigurable circularly polarized microstrip antenna with single feed line, feeding with Proximity coupled method. Antenna is capable to radiate LHCP and RHCP with the help of proper switching action and reconfigurable feedline. The third design is to design and develop dual feed Quadri-Polarization States microstrip patch antenna feeding with microstrip line. With the help of two feedline and 4 diodes antenna is capable to radiate VLP, HLP, LHCP, RHCP. On the patch two opposite corners are slotted and connect by using two PIN diodes. The forth design is to design and develop polarization reconfigurable microstrip antenna with single feedline, feeding with microstrip line. Antenna is capable to radiate electromagnetic wave of various pattern like LP, LHCP, RHCP. Various S-parameters, surface current distribution, axial ratio, and radiation patterns are shown for various antennas. Antennas are capable to radiate various orthogonal patterns which increase the diversity gain. Therefore, antenna have a features of multipath effects reduction i.e. reduction of fading and interference and antenna can be used as polarization diversity array

碩士
國立交通大學
電信工程系所
94
In this thesis, novel reconfigurable patch antennas for quadri-polarization diversity are designed and fabricated. To satisfy the requirement of polarization diversity in the integrated communication systems, we propose the idea of switching the polarization statuses of antennas by controlling the bias of pin diodes in this thesis. This way, antennas are operated between dual-linear and dual-circular polarization. The polarization statuses of antennas are decided by either different resonating structures or different feeding signals. Therefore, by controlling the bias of pin diodes to change the resonating structures or different feeding signals, quadric-polarization antennas can be realized easily. Presently few antennas can be operated both in dual-linear and dual-circular statuses. In this thesis we apply pin diodes in patch antenna and aperture coupled antenna. By the two design methods mentioned above, single antenna can be operated between dual-linear polarization and dual-circular polarization.

博士
國立臺灣科技大學
電子工程系
102
In this thesis, we propose the two design method of antenna, one is reconfigurable of radiation pattern and another one is reconfigurable of polarization. First, the radiation pattern reconfigurability is realized straightforwardly with an employment of a detached magnetodielectric slab placed in the vicinity of the antenna structure. We determine the monopole antenna which is simple to research. Then, discuss on using magnetodielectric slab placed in the vicinity of the antenna structure, like non-porous, single hole, porous slab. Therefore, we define ‘magnetic antenna”. The antenna structure with single hole or porous slab, we define ‘porous magnetic antenna”. As above results, through the use of a magnetodielectric material on the back of the RFID reader antenna, the antenna gain is increased 2.26dBi. This enhancement has increased the operational range behind the the antenna by nearly 70% for far-zone reading. Secondly, we use diode to design reconfigurable of polarization, which able to adjust antenna. We use a circular patch antenna with a ring slot on it. On the ring slot, diode switches are placed at 30° interval. We propose a design of polarization diversity antenna which is able to generate six Lps st a 30° interval (0°, 30°, 60°, 90°, 120°, 150°) with the same antenna characteristics due to symmetry in geometry of the antenna. Measured results are in good agreement with the simulated, proving the correctness of our design. Two reconfigurable of antenna methods shown in simulated and measured results, the demonstrated antennas own a low-cost, adjust-easy are expected to find application in noise or interference suppression for the mobile devices in different environment. It’s the purpose on this research.

碩士
國立交通大學
電信工程系所
95
This thesis introduces the design of a patch antenna fed by L-shaped capacitive coupling probes, along with a dual-band branch line coupler designed by the even-odd mode analysis method we proposed in this thesis and the wideband switching circuit to achieve our purpose of the dual-band quadri-polarization diversity antenna. In nowadays, WiMAX is becoming more popular in wireless communication application besides WiFi. This antenna structure operates at WiFi (2.45GHz) and WiMAX (3.5GHz) spectrum. The transmission distance, bandwidth and transmission speed of WiMAX operation are better than that of WiFi The advantages of polarization diversity antenna include providing more channels by producing more polarization modes to enhance the capacity and receiver sensitivity and reducing the effect of multi-scattering environment. Based on these principles, we propose an antenna structure which can produce dual linear and dual circular polarizations. There are three parts in our design: first, the dual-band branch line coupler provides two equal-power signals with 90° or -90° phase difference in each operating band. Second, the wideband switching circuit controls the two output powers of branch line coupler to excite the antenna structure for producing linear polarization wave or circular polarization wave. Third, the L-shaped fed conventional planar patch antenna is provided to overcome the coupling effect.

碩士
國立臺灣大學
電信工程學研究所
105
This thesis presents a reconfigurable antenna with full polarization diversity for indoor WLAN IEEE802.11n/ac applications. First, we proposed the annular ring slot antenna with four small apertures where an aperture is loaded with a diode. By controlling only one diode and the feed line location, the proposed antenna can achieve the full polarization configurations – V-pol, H-pol, RCP, and LCP. The design concept was verified by HFSS simulation and implemented on a 1.6mm thick -FR4 PCB. This thesis provides the design procedures, parameter study, and performance comparison between the simulation and measurement. Second, we realized the prototypes with three progressive phases. In Phase 1, we used different layouts on the printed antennas to build individual antennas of various fixed polarizations. In Phase 2, we added a diode to one of the small apertures and employed the bias circuit to control between the linear and the circular polarization of a feed line. To achieve better AR of circular polarization, we used the TRL calibration method to extract the accurate circuit parameters of the employed diode. In Phase 3, we added a switch IC for the feed lines of orthogonal orientation to achieve a reconfigurable design of full polarization diversity.

yes
This paper presents a compact-size, low-cost smart antenna with electronically switchable radiation patterns, and reconfigurable polarizations. This antenna can be dynamically switched to realize three different polarizations including two orthogonal linear polarizations and one diagonally linear polarization. By closely placing several electronically reconfigurable parasitic elements around the driven antenna, the beam switching can be achieved in any of the three polarization states. In this design, a polarization reconfigurable square patch antenna with a simple feeding network is used as the driven element. The parasitic element is composed of a printed dipole with a PIN diode. Using different combinations of PIN diode ON/OFF states, the radiation pattern can be switched toward different directions to cover an angle range of 0◦ to 360◦ in the azimuth plane. The concept is confirmed by a series of measurements. This smart antenna has the advantages of compact size, low cost, low power consumption, reconfigurable polarizations, and beams.

博士
義守大學
電機工程學系
102
This dissertation presents a series of design of active reconfigurable polarization microstrip antenna in wireless local area network. The proposed antennas are designed as the single feed structure with the microstrip circuit module. The circuit module consists of microstrip line, pass component and active component. The circuit module can be managed to control the surface current on radiator and function as the reconfigurable switching of circular polarization modes for the proposed antennas. First antenna design uses the capacitor to control the phase of microstrip line and being reached the dual circular polarization. Second antenna design and third antenna design can be switched the circular polarization modes by using of the PIN diodes and the perturbing structure. Fourth antenna design is the stack structure with dual circular polarization. In this dissertation, the advantages of the four antennas are the small size, the function as reconfigurable polarization and the dual circular polarization radiation. The proposed antennas can be improved the receiving quality of products and reduced the number of antennas on the system. Details of the antenna design are shown, and the simulated and measured results are also presented and discussed.

碩士
國立臺北科技大學
電子工程系
107
This thesis presents a reconfigurable antenna based on a circular patch antenna with a ring slot on which a total of 16 diodes are placed at an equal interval of 22.5°. By manipulating the on-off states of the diodes, the antenna can operate at different frequencies and receive incoming signals at different polarizations. The design process features the use of genetic algorithm to find the appropriate antenna geometrical parameters and Matlab program to find the suitable diode states at each frequency. Our goal is to cover all frequencies from 0.7 - 3 GHz with return loss greater than 6 dB and radiation efficiency greater than 40 %. Although the measured return loss of the realized antenna does not meet the target, still 79 % of the frequencies satisfy the 6 dB return loss criteria.

碩士
國立彰化師範大學
電機工程學系
102
Antennas designs based on a compact feeding network are studied in this thesis. First, three quadrature couplers, including a traditional coupler, a size-reduced coupler, and a quasi-lumped coupler, are designed and their performances are investigated. According to the obtained results, the quasi-lumped quadrature coupler has a relatively narrow operation bandwidth, but it has a much smaller size than the others, which is required for mobile devices of present wireless communication systems. Consequently, two antenna designs based on the quasi-lumped coupler are developed. One is a circularly-polarized square-ring patch antenna suitable for GPS applications. In this design, the coupler is placed in the inner slot of the ring patch, and it is used to simultaneously excite TM01 and TM10 mode of the antenna. From the measured results, the antenna can generate good broadside radiation with right-handed circular polarization at 1.575 GHz; in addition, the 10dB-return-loss and 3dB-axial-ratio bandwidth are 3.9 % and 1 %, respectively. The other design is for polarization reconfigurable antennas which are helpful to reduce the multipath effects. The design adopts a stacked square-ring microstrip antenna, and the polarization switching is realized with a 1 to 4 reconfigurable feeding network composed of the quasi-lumped coupler and several PIN diodes. A prototype that integrates the feeding network into the inner slot of the lower square-ring patch of the stacked patch antenna is constructed. Experimental results show that the prototype can well perform the switching among dual orthogonal linear polarizations and dual orthogonal circular polarizations within a 3.3 % bandwidth centered at 1.98 GHz.

An antenna is one of the essential elements in a wireless system, that converts the guided waves in an electronic circuit to unguided waves in the air and vice versa. They are often designed according to the specifications of the underlying system. Compact antennas are required in miniaturised systems such as those used in an aircraft. They are designed by modifying or appending the antenna with additional structures or circuit elements without degrading its responses. In this thesis, the design of compact antennas is investigated with metasurface for two unique purposes - i. wideband applications for detection/sensing application, and ii. spatial modulation to communicate a multipath environment. For wideband applications, a spiral antenna is considered a primary radiator due to its wideband impedance matching and circular polarization (CP) response with simple and planar geometry. It has a bidirectional radiation pattern on either side of the structure, along the axis of the antenna. But in many practical applications, a single-sided radiation pattern is extracted by placing it above a metallic body of a ship or aircraft, which disturbs the freestanding radiation response of the antenna. A conductor placed more than half a wavelength away from the spiral reduces the boresight gain significantly at high frequency, whereas the same placed too close to the antenna degrades the matching and polarization performance at low frequency. These issues have been addressed over years with different techniques, but the design of compact spiral still possesses significant challenges especially when a frequency band of 1-18~GHz is considered. As this research work begins, the spiral is placed at different heights above a metallic conductor and the effects are observed over the considered frequency range. It is followed by an investigation with profiled metallic geometries to combine the benefits of varying antenna heights at different frequencies. Based on these observations, a compact spiral antenna is designed by placing it above a modified conical conductive backing to radiate a CP wave over a wide frequency band. In the next part of this thesis, some of the challenges at low frequencies are addressed using different absorber techniques when the spiral is kept extremely close to a conductor. A hybrid technique consisting of absorbing material and resistors is proposed to design such a compact spiral antenna for wideband application. To improve the performance below 2~GHz, a wideband metasurface absorber is investigated with the spiral. The metasurface possesses significant electromagnetic absorption at low frequency and has been used to design a spiral antenna for 1-18~GHz with an extremely low profile. Another work with a compact spiral antenna approaches to tilt its main beam over a wide frequency range. This investigation is required to compensate for the shift in the antenna main beam due to the supporting structure or to tilt the antenna main beam in a given direction for different purposes. A semicircular lens made of lossy dielectric material is placed above a compact spiral to fulfil this requirement. Effects of different material properties and lens profiles are investigated to arrive at the final design. Since placing the lens along the spiral affects the compactness of the antenna and disturbs the planar profile required in a flush mounting configuration, a sectoral metasurface is designed and printed on the backside of the antenna substrate. The metasurface possesses effective material properties to tilt the antenna main beam at a consistent angle. For all cases, numerical investigations were carried out to optimize the antenna geometries followed by prototyping and characterization of some of these structures. The measured results are compared with the simulated outcomes and the numerical predictions have been verified. This required the design and realization of a wideband balun and appropriate fixtures to integrate various parts of this antenna in a flush-mount arrangement. For a unique wireless application with a compact antenna, a digitally reconfigurable metasurface in the vicinity of a patch antenna is proposed, to realize for the first time a modulator for a spatial modulation technique known as media-based modulation (MBM). MBM facilitates a fast, secure, and multiuser wireless link in a multipath environment (e.g., indoor or office environments) by exploiting the multipath components of the channel. The metasurface works as an electromagnetic window as the power flowing through the unit cell can be electronically controlled by switching a PIN diode embedded within. A significant difference in transmission coefficient is observed between the two switching states of the unit cell. A meander geometry is used to make it compact and the diode is placed between the meander and one of the two contiguous strips that provides the necessary biasing to the diode. Numerical investigations are carried out to characterize the unit cell, and to optimize the array dimensions and the gap between metasurface and antenna. A prototype of the array is fabricated with the necessary control circuitry and a complete wireless link is set up to communicate in a real-time environment. Experiments are carried out in different scatter free and scattering environments in line of sight and non-line of sight configurations to validate the theoretical predictions of MBM. The effects of multipath as a factor that improves communication performance are also validated. In the end, data transmission over a wireless link is also demonstrated using this scheme.
Ministry of Education, Govt. of India and Thales Defence Mission Systems