De nos jours, les communications sans fil sont devenues un moyen incontournable et universel d'échange d'un large éventail d'informations entre différents systèmes, certains d'entre eux étant en mouvement comme des drones parmi tant d'autres. Dans le contexte de cette thèse nous considérons une liaison entre un projectile et une station de base. La géométrie de la structure ainsi que les contraintes aérodynamiques d'un tir balistique impliquent l'utilisation d'antennes patchs dans la partie conique à l'avant du projectile. Ce type d'antenne est facile à intégrer à une plate-forme en tant que réseau conformé tout en respectant les contraintes d'encombrement. Ces communications doivent être fiables et discrètes dans un environnement perturbé ou hostile. Les diagrammes de rayonnement du réseau d'antennes doivent présenter des caractéristiques spécifiques, notamment dans le cas particulier d'objets volants et possédant une rotation en roulis (rotation autour de son axe) qui impliquent l'utilisation d'un réseau phasé et commuté par rapport à sa position. Une antenne qui présenterait un rayonnement fixe assurerait une liaison avec un interlocuteur, mais rayonnerait également dans d'autres directions sensibles ce qui pourraient interférer avec la communication principale. La solution qui consiste à activer et désactiver des sous-réseaux verticaux afin d'orienter le lobe principal dans la plan orthogonal à la pointe semble être en accord avec les contraintes de la structure tournante. Un réseau conique a été étudié puis 2 prototypes ont été fabriqués, dont un à l'ISL. Les sous-réseaux sont répartis de manière égale autour de la pointe de façon à pouvoir rayonner dans toutes les directions. De plus, chaque sous-réseau est composé de trois éléments ce qui permet d'orienter également le lobe principal dans le plan longitudinal de la pointe (le long de l'axe du projectile) grâce à un dépointage électronique. Un système électronique de formation de faisceaux a été développé dans le but de contrôler 12 éléments rayonnants. Le réseau d'antennes ainsi que le circuit de répartition ont été caractérisés dans un premier temps de manière indépendante afin d'optimiser les lois de phase nécessaires à dépointer le lobe à partir des pondérations mesurées. Au final, le réseau de 12 éléments associé à son système d'alimentation dédié a été mesuré dans les chambres anéchoïques de DGA-MI et de l'ISL et les mesures sont en accord avec les simulations. / Nowadays wireless communications have become a useful and universal mean to exchange a wide range of information between different systems, some of them being moving, as UAVs among others. In this context we consider here the link between a projectile and a base station. The shape of the structure and the aerodynamic constraints involve the use of patch antennas in the conical front part. This class of antenna is easy to be integrated into the platform as a conformal array, while respecting space constraint. Communications have to be reliable and discrete in disturbed or hostile environment. Antennas array radiation patterns must have some specific characteristics, in particular in the case of flying objects with spin which involves the use of a switched phased array considering its roll position. A fixed-radiation pattern antenna may presents a relevant level or gain toward the interlocutor, but also toward sensitive directions, in which may be located others systems, interfering with the current communication. The solution to switch on and off vertical sub-arrays to steer the beam in the azimuthal plane seem convenient ant fitting the requirements of rotating platform. A conical phased array was studied and two prototypes were manufactured, one at ISL. Sub-arrays are distributed around the conical shape in order to be able to radiate in each direction. Moreover, each sub-array are composed of three radiating elements allowing to steer the main antenna beam in many direction (along the projectile fuze axes). A beam forming network was developed to control the 12 radiating elements conical array. The antenna array and the feeding network were characterized independently in order to optimized the phase of each radiating element. Finally, measurements were done on the whole system in the DGA-MI and ISL anechoic chambers and are in good agreement with simulation results.

L'objectif de cette thèse est d'exploiter les phénomènes des ondes de fuite pour améliorer les performances des antennes classiques à ouverture pour les applications spatiales. Ici, nous considérons des configurations planaires où les ondes de fuite sont excitées entre un plan de masse et un superstrat partiellement réfléchissant. Des réseaux de petites ouvertures sur le plan de masse sont utilisés pour alimenter les antennes considérées. Les structures avec superstrat sont développées en configuration réseaux simples ou réseaux à commande de phase, considérées intéressantes en termes de flexibilité du système pour des liens satellitaires de nouvelle génération.Pour étudier efficacement ces antennes, nous avons développé un outil d'analyse basé sur une approche spectrale avec fonction de Green. Cet outil permet d'analyser les structures proposées en prenant en compte l'impact du couplage mutuel entre les éléments sur les performances de rayonnement avec une réduction du temps de calcul et d'utilisation de mémoire.L'augmentation du gain des structures à ondes de fuite peut ouvrir la voie à la réduction du nombre d'éléments des réseaux associés, et donc des commandes en amplitude et phase. Dans une configuration à ondes de fuite, chaque élément du réseau rayonne avec une ouverture équivalente plus grande, augmentant ainsi l'espacement entre les éléments sans affecter le gain global de la structure. Comme largement expliqué dans le manuscrit, les solutions à ondes de fuite représentent par conséquent un avantage majeur pour les antennes du segment utilisateur.En plus de l'amélioration du gain, la technologie à ondes de fuite peut être efficacement exploitée pour synthétiser le diagramme de rayonnement, en choisissant correctement les paramètres de conception de l'antenne. Cette caractéristique peut être utilisée dans les réseaux à commande de phase, pour produire un diagramme d'élément qui minimise les pertes par dépointage et qui filtre les lobes de réseaux. Une procédure de synthèse pour des antennes réseaux raréfiés à ondes de fuite est ainsi présentée dans le manuscrit, ainsi qu'une nouvelle configuration de réseaux avec superstrat irrégulier. Ce dernier permet de réduire les lobes secondaires de l'antenne en utilisant une excitation uniforme. Cette dernière configuration montre clairement que la capacité de modifier le diagramme de rayonnement est la caractéristique la plus attrayante des antennes planaires à ondes de fuite, pour être utilisée dans des solutions de réseaux à commande de phase. / The objective of this thesis is to exploit the leaky-wave phenomena to enhance the performance of classical aperture antennas for space applications. Here, we consider planar configurations where the leaky modes are excited between a ground plane and a partially reflective superstrate. Arrangements of small apertures opening on the ground plane are used to feed the antennas under study. The superstrate-like leaky-wave structures are developed in array or phased array configurations, considered of interest in terms of flexibility of the system for next generation satellite links. In order to efficiently study planar leaky-wave arrays, we have developed an analysis tool based on a Green's function spectral approach. The developed tool allows to precisely analyze the proposed structure by taking into account the impact of the mutual coupling among the elements on the radiation performance of the whole antenna. In addition, it can handle extremely large structures in terms of wavelengths with a small computational effort with respect to commercial tools. In particular, the gain enhancement of leaky-based structures can pave the way to the reduction of the number of elements of the associated phased arrays. In a leaky-wave configuration each element of the array will radiate with a larger equivalent aperture allowing a larger spacing among elements without affecting the final gain of the whole structure. This aspect is particularly important in the case of phased arrays, where phase shifters and control cells are, typically, the most expensive components of the system. As extensively explained in the manuscript, antennas for user segment might find the highest benefit by using leaky-wave solutions. Besides the gain enhancement, the leaky-wave technology can be effectively exploited to conveniently shape the radiation pattern by properly engineering the design parameters of the antenna. This capability can be used in phased arrays to generate a convenient element pattern to minimize the scan losses and filter the grating lobes appearing in the visible space when dealing with periodicities larger than a wavelength. Therefore, a synthesis procedure for thinned leaky-wave arrays is presented in the manuscript. Also, a novel array configuration, the irregular superstrate array, is presented. The irregular superstrate allows the reduction of the side lobes of the antenna below -20 dB in the considered 2.5 % band, using a uniform excitation. This last configuration clearly shows that the shaping capability of leaky-wave antennas is the most appealing feature to be used in phased array solutions.

This thesis deals with the design of cost-effective large-scale RFID networks from both software and hardware aspects. To start with, different computer-aided tools were developed to maximize performance. The first set of algorithms focused on the elimination of redundant readers to minimize the cost and interference in large-scale RFID networks. For validation, uniform reader coverage was assumed, as widely used in most available publications. Then, both omni-directional and directional commercial reader antenna data were included for more reliability. Besides redundancy, an efficient physical placement of readers was also investigated by considering both uniform and random distribution over space. For this purpose, genetic-based algorithms have been proposed to increase reader coverage using commercial reader antenna beams. Energy consumption is also a critical design parameter for dense RFID networks. Therefore, a third set of algorithms was developed to efficiently minimize the energy consumption of large-scale RFID systems. Note that all above optimization techniques were achieved without compromising the whole RFID network performance. To further optimize cost and performance of large-scale RFID networks, a hardware approach through reader antenna design has been considered. In fact, since different RFID frequency bands have been assigned worldwide, large-scale RFID networks implemented in industrial parks, airports, or international trade zones, may deal with imported merchandise using tags operating at different frequencies. Therefore, in-house single and dual-band microstrip and CPW fed monopole antennas were successfully designed and tested to improve system adaptability to various RFID standards. These antennas were designed using both electromagnetic commercial simulators (HFSS) and in-house FDTD-based techniques. Finally, to further extend dense RFID network capabilities, one may implement a substantial number of readers and antennas with small reading ranges to cover a large monitoring area, or use high gain phased array antenna system for an extended reading range of an RFID reader for a smaller number of total reader deployments. Therefore, a phased antenna array system can be an efficient alternative for dense RFID networks. Thus, a switched beam network to control the phase of the radiating elements of the array has been successfully designed and tested.

La simulation numérique est un outil indispensable pour la résolution de problèmes électromagnétiques. Le temps de calcul ainsi que la précision des résultats dépendent du niveau de description utilisé et des dimensions électriques du problème analysé. Dans le cas de figure où il est nécessaire de modéliser un environnement électriquement grand, l'emploi de méthodes classiques comme la méthode des différences finies dans le domaine temporel (FDTD) se heurte à des difficultés en termes de temps de simulation. Cet aspect devient particulièrement problématique quand l'analyse doit être menée pour plusieurs valeurs d'un ou plusieurs paramètres définissant le problème étudié. Face à cette variabilité et afin d'éviter la multiplication de simulations coûteuses, Il est nécessaire d'opter pour des méthodes appropriées. Les travaux de cette thèse sont consacrés au développement d'une nouvelle approche permettant de résoudre de manière efficace l'aspect variable rencontré dans un problème multiéchelle. Cette nouvelle méthode issue de l'association de la FDTD à Grille Double (DG-FDTD) avec un modèle de substitution se nomme la MM-DG-FDTD (Macro-Modèle basé sur la DG-FDTD). L'emploi de la DG-FDTD vise à traiter l'aspect multi-échelle en divisant le problème étudié en sous-volumes FDTD possédant chacun ses propres paramètres de simulation. L'utilisation d'un modèle de substitution rapide construit en peu de simulations électromagnétiques permet de remplacer rigoureusement et rapidement la dernière simulation de la DGFDTD. Après avoir validé le bon fonctionnement du modèle de substitution sur des cas simples, une utilisation de la MM-DGFDTD est effectuée sur deux applications inscrites dans deux contextes : la dosimétrie numérique et le couplage entre antennes. La première propose d'estimer la valeur du champ électrique à l'intérieur de l'oeil gauche d'un modèle de corps humain. Ce dernier est soumis au rayonnement électromagnétique d'une antenne localisée sur un véhicule. Cette étude est effectuée pour un grand nombre de positions du corps autour du véhicule. La seconde application consiste à évaluer la valeur du coefficient de transmission entre deux antennes ULB (Ultra-Large Bande). La position de l'antenne de réception évolue au sein d'un grand environnement. Pour ces deux études, la MM-DG-FDTD montre sa capacité à donner des résultats rapides et précis en comparaison d'une utilisation classique de la DG-FDTD. / Numerical modelling is an essential tool for solving electromagnetic problems. The computation time and the accuracy of the results depend on the description level used and electrical dimensions of the analyzed problem. When it is necessary to model an electrically large environment, the use of conventional methods such as the finite difference time domain (FDTD) face difficulties in terms of simulation time. This becomes particularly problematic when the analysis must be carried out for several values of one or more parameters defining the studied problem. Considering this variability aspect and in order to avoid multiplication of costly simulations, it is necessary to choose suitable methods. This thesis aims to develop a new approach to solve effectively the variable feature encountered in some multi-scale problems. This new method called the MM-DG-FDTD (MacroModel based Dual Grid-FDTD) results from the association of the Dual Grid- FDTD (DG-FDTD) method with a substitution model. The use of the DG-FDTD permits to treat multiscale aspect dividing the studied problem into FDTD sub-volumes. Each step has its own simulation parameters. The fast substitution model built in few electromagnetic simulations replaces in a rigorous and efficient way the last expensive DG-FDTD simulation. The proper operation of the substitution model is firstly validated using simple cases. Next, a use of the MM-DG-FDTD is performed on two applications belonging to two contexts: numerical dosimetry and antennas coupling. The first one proposes to estimate the value of the electric field inside the left eye of a human body model. It receives electromagnetic radiation from an antenna located onboard a vehicle. This study is carried out for a large number of positions of the body around the vehicle. The second application is to assess the value of the transmission coefficient between two UWB (Utra-Wide Band) antennas. The position of the receiving antenna changes in a large environment. For both studies, MM-DG-FDTD shows its ability to give fast and accurate results compared to a classic use of the DG-FDTD.

The Conformal C-Band/Multi-band Antenna project will support the AWS-3 auction by providing the technology to integrate C-Band or multi-band telemetry(TM) antennas on test articles such as missiles, weapons, or aircraft. These test articles would then provide C-Band or multi-band TM data to ground station receivers that are relocated to the C-Band frequency range through the AWS-3 Spectrum Relocation Fund program. This project would advance the technology of antennas in the C-Band region for test article TM integration. Successful use of C-Band and Multi-Band antennas for aeronautical mobile telemetry (AMT) on test and training ranges is dependent on the advancement of key technologies. This paper will detail the technology areas being matured by this project as well as the capabilities to be demonstrated.

In this thesis, an antenna reduction technique in Multiple Input Multiple Output (MIMO) systems, which is called Code Shift Keying (CSK) Modulation, is introduced. With the use of Walsh Hadamard orthogonal spreading codes, we overcome the biggest drawback of conventional Spatial Modulation (SM) which is the antenna index estimation errors due to channel correlation. Also SM fails to perform in non normalised channel conditions. The combination of orthogonal spreading codes and antenna devices, as a means to convey information at the receiver, results in a remarkable performance improvement at the receiver.Moreover, an improved scheme that uses half the amount of spreading codes so as to represent the total number of information bits has been introduced leading to an important reduction in bandwidth usage. By maintaining the net spreading levels of the system we attain remarkable performance improvements.A technique called Polarisation Assisted Space Shift Keying Modulation (PASSK) has also been proposed which manages to exploit the polarisation domain and it is able to outperform the conventional SM technique as well as the Maximal Ratio Receiver Combine (MRRC) and Vertical-Bell Laboratories Layered Space-Time (V-BLAST) schemes. A new precoding scheme that manages to either eliminate or exploit the cross polarisation effects has also been proposed as a complementary study of the PASSK scheme.As modern and future communications show a rising demand for higher data transmission rates, network coding is increasingly incorporated in wireless communication standards. In harmonisation with this trend, this thesis discusses the main state-of-art network coding schemes. The contribution here includes a number of innovative schemes that are able to further increase throughput. Finally, the employment of network coding is discussed in conjunction with CSK Modulation resulting to further improvement in terms of throughput as well as Bit Error Rate (BER) performance at the cost of increased bandwidth usage.

In 2014, Toyon Research Corporation donated a 6’x6’x8’ anechoic chamber to the Cal Poly EE department to advance student education in the areas of antennas and wireless communications. An anechoic chamber is a room designed to suppress electromagnetic radiation reflections so that accurate measurement of radio frequency (RF) systems such as wireless radios and antennas can take place. Despite the fact that Cal Poly already has a larger anechoic chamber, primarily used for antenna characterization, it is the purpose of this project to design, code, and equip the new chamber so that it performs at least as good, or better than, the existing chamber. Radiation pattern is a key characteristic that describes the directionality or gain of an antenna, and it is important for quantifying and qualifying how an antenna will perform as part of a wireless communication system. Radiation pattern measurement can be time consuming because it requires measuring an antenna’s transmission or reception in in all directions. In both the old and new antenna measurement systems (AMS), a vector network analyzer (VNA) measures signals transmitted between the antenna under test (AUT) and an RF field probe within the antireflective environment of the anechoic chamber. The new system synchronizes VNA measurement with the rotation of the AUT using the automation software LabVIEW and a Sunol Sciences FS-121 antenna positioner. Then, Matlab plots the data collected by LabVIEW as well as calculates useful antenna metrics including half power beam width (HPBW) and directivity. LabVIEW also makes the AMS easy to operate because of its graphical user interface. The new anechoic chamber completes measurements faster than Cal Poly’s existing chamber, with good accuracy and ease of use. The new chamber works best with smaller antennas at frequencies up to 6 GHz and beyond. Radiation patterns have good SNR, and match with simulations and measurements done in the larger chamber. However, due to its smaller size the new AMS is not a replacement for the existing larger system when testing antennas larger than 1 m or at frequencies below 2 GHz.

The main goal of this research is to develop algorithms to facilitate the use of a new type of antenna, called multifunctional reconfigurable antenna (MRA). Traditional antennas have fixed radiation properties which cannot be changed to adapt to different environments. To solve this problem, MRAs, which can dynamically change its operation frequency, radiation patter, and polarization, has gained a significant interest recently. Such antennas can support multiple radio access technologies with different sets of operational requirements. Reconfigurable antennas are considered smart antennas. The efficient use of smart antennas requires efficient and smart underlying algorithms. This dissertation focuses on developing efficient algorithms to exploit the reconfigurability of MRAs to tap on the superior performances offered by additional degrees of freedom compared to legacy antenna systems.

Les sources infrarouges sont indispensables à la détection locale de gaz dans de nombreux domaines, que ce soit pour l'environnement (détection de polluants et gaz à effets de serre) ou la défense (détection de menaces biologiques et chimiques). Elles sont également nécessaires en tant que mires de calibration pour le développement de caméras multispectrales infrarouges. Pour toutes ces applications, il est nécessaire de disposer de sources performantes, capables d'émettre un rayonnement spécifique dans une direction donnée. L'objectif de cette thèse est de concevoir des sources thermiques infrarouges compactes et à coût modéré, à spectre accordable et à pertes réduites, pouvant être juxtaposées dans un même dispositif. Pour cela, ces travaux s'organisent autour de deux axes. Le premier concerne l'étude de nouveaux matériaux nanostructurés résonants, appelés métamatériaux ou métasurfaces selon les directions de la structuration, permettant de contrôler l'émissivité spectrale et spatiale afin de maîtriser la réponse spectrale en tout point. Cette étude repose à la fois sur des simulations numériques et sur des mesures expérimentales et démontre le potentiel de ces résonateurs pour la conception de sources thermiques accordables. Cependant, ces matériaux étant composés de métal, ils présentent des pertes par absorption dans l'infrarouge qui limitent leurs performances. Le deuxième axe de recherche est alors de gérer les pertes liées à l'utilisation de métaux grâce à une ingénierie des champs dans des métamatériaux, menant à des émissions spectralement très fines. Les résultats obtenus sur ce contrôle des pertes ouvrent de nombreuses perspectives pour tout le domaine des métamatériaux. / Infrared sources are essential for local gas detection for civil applications (detection of pollutant and greenhouse gas) or military applications (detection of chemical and biological threats). They are also used as calibration targets for the development of multispectral infrared cameras. For these applications, the sources must be efficient and able to emit a specific light in a given direction. The aim of this thesis is to develop infrared thermal emitters with the following features: low cost with a compact volume, with a tunable spectral response and low losses, able to be juxtaposed on the same device. This work begins with the study of new resonant nanostructured materials, called metamaterials or metasurfaces according to the direction of the structuration, that spectrally and spatially control the emitted light up to the wavelength scale. This study relies on numerical simulations and experimental measurements and demonstrates the potential of these resonators as tunable thermal sources. However, due to the use of metals in these materials, their performance is limited by metal losses. The second study of this work is then to deal with these losses thanks to a field engineering in metamaterials, leading to very narrow spectral responses. The results on this loss control open up promising breakthroughs in the plasmonic and metamaterials field

Phased array systems present desirable antenna features like beam steering and high gain. However, due to their high cost, civilian applications cannot generally afford them, restricting their usage to military. Hardware involved in phased array systems is expensive and the number of devices is high, since there is usually one device of each kind (filter, amplifier, shifter..) for each individual antenna. Alternative techniques, mainly based on TDMA, have been developed looking for lowering the number of elements in the system. However, these approaches increase the system bandwidth, multiplying it by a factor of $N$ (Number of antennas), as they use redundant information. In this thesis, a novel phased receiver, based on an economic sampling scheme is proposed. All the elements in an array receive a common information (signal amplitude) and a unique information (relative delay between elements). The idea is to sample only the information required to reconstruct the transmitted signal and discard the redundant one. This idea is achieved by sampling just one antenna during each RF cycle and then gathering all the information taking in account the relative delay between different antenna elements. The proposed technique is mathematically proved and validated by simulation. As a first approach, the equation for the received signal in the frequency domain is derived for a linear array. The radiation pattern and the received signals are simulated for equally spaced planar and linear arrays. Bandwidth signal transmission is demonstrated and tapering effects are shown. After that, the proposed technique is expanded for arbitrary structures and the resulting system bandwidth is enhanced by using different sampling order sequences. / Master of Science