The objective of the proposed research is to develop solutions for High-Performance Low-Cost Passives for Radar, Identification, and Communication Applications up to mm-Wave Frequencies. This research will bring to the table potential solutions that will meet three main requirements: small size (or low weight), high performance, and low cost. This research embarks on antenna design and development for passive RFID tags on LCP substrates, and then a transition towards lower cost modules investigates and explores the possibilities of using paper as RF substrates with inkjet printing as a low cost fabrication technology. Modules such as dual band antenna for Wifi frequencies (2.4 GHz and 5 GHz) and UWB (up to 10GHz) on paper substrate using inkjet printing are presented. This work then bridges into developing higher frequency modules. These include: highly selective filter design on LCP for X-band Radar application to be used as a benchmark for an easy adjustment for higher frequencies, and antenna modules LCP using inkjet printing for communication such as mm-Wave WLAN or WPAN. A transition into mm-Wave Modules then takes place for the general realization of low-cost high-performance mm-Wave modules and more specifically the low cost automotive radar. After proposing an architecture for integrated mm-Wave module, this work then investigates 2D/3D interconnections (and their integration with antennas) on LCP using conventional etching design guidelines up to 100GHz. Antenna arrays that are implemented with phase shifters for beam steering are then designed using edge fed and multilayer technology. Furthermore, crosstalk reductions for highly dense transmission lines are analyzed via simulations for the optimum performance and space saving of such mm-Wave modules such as the IC interface where space restrictions are strictly enforced.

Capacity improvement of Wireless Communication Systems is a very important area of current research. The goal is to increase the number of users supported by the system per unit bandwidth allotted. One important way of achieving this improvement is to use multiple antennas backed by intelligent signal processing. In this thesis, we present methods for blind separation of co-channel BPSK signals arriving at an antenna array. These methods consist of two parts, Constellation Estimation and Assignment. We give two methods for constellation estimation, the Smallest Distance Clustering and the Maximum Likelihood Estimation. While the latter is theoretically sound,the former is Computationally simple and intuitively appealing. We show that the Maximum Likelihood Constellation Estimation is well approximated by the Smallest Distance Clustering Algorithm at high SNR. The Assignment Algorithm exploits the structure of the BPSK signals. We observe that both the methods for estimating the constellation vectors perform very well at high SNR and nearly attain Cramer-Rao bounds. Using this fact and noting that the Assignment Algorithm causes negligble error at high SNR, we derive an upper bound on the probability of bit error for the above methods at high SNR. This upper bound falls very rapidly with increasing SNR, showing that our constellation estimation-assignment approach is very efficient. Simulation results are given to demonstrate the usefulness of the bounds.

Concurrent cooperative transmission (CCT) occurs when a collection of power-constrained single-antenna radios transmit simultaneously to form a distributed multi-input and multi-output (DMIMO) link. DMIMO can be a means for highly reliable and low-latency cooperative routing, when the MIMO channel is exploited for transmit and receive diversity; in this context, the range extension benefit is emphasized. Alternatively, DMIMO can be a means for high-throughput ad hoc networking, when the MIMO channel is used with spatial multiplexing. In both cases, concatenated DMIMO links are treated. The key contribution of this dissertation is a method of pre-synchronization of distributed single-antenna transmitters to form a virtual antenna array, in the absence of a global clock, such as a global positioning system (GPS) receiver or a network time protocol (NTP) to provide reference signals for the synchronization. Instead, the reference for synchronization comes from a packet, transmitted by the previous virtual array and simultaneously received by all the cooperative transmitters for the next hop. The method is realized for two types of modulation: narrowband non-coherent binary frequency-shift keying (NCBFSK) and wideband orthogonal frequency division multiplexing (OFDM). The pre-synchronization algorithms for transmission are designed to minimize the root-mean-square (RMS) transmit time, sampling and carrier frequency error between cooperative transmitters, with low implementation complexity. Since CCT is not supported by any existing standard or off-the-shelf radios, CT must be demonstrated by using software-defined radios (SDRs). Therefore, another contribution is a fully self-contained and real-time SDR testbed for CCT-based networking. The NCBFSK and OFDM systems have been designed and implemented in C++ and Python programming languages in the SDR testbed, providing practical performance of the CCT-based systems.

Several emerging wireless applications require direct transmission between mobile terminals. Examples of these applications are mobile ad-hoc wireless networks, intelligent transportation systems, relay-based cellular networks, and future combat systems. Development of these mobile-to-mobile (M-to-M) systems depends on a good characterization of channel propagation. Another important consideration in modern communication systems is the use of multipath propagation to improve reliability and capacity of wireless systems. This is achieved by employing multiple antennas in multiple-input multiple-output (MIMO) systems and using techniques such as transmit and receive diversity. Considering the demand for high-speed wireless services, MIMO M-to-M systems are the leading candidates for future communication systems. To enable the successful design of MIMO M-to-M systems, our research focuses on modeling of MIMO M-to-M multipath fading channels and on diversity techniques for MIMO systems. Specifically, we propose two-dimensional (2-D) and three-dimensional (3-D) MIMO M-to-M statistical channel models that encompass narrowband and wideband MIMO channel scenarios for macro- and micro-cell environments. Furthermore, we validate the new models against measured data and find very close agreement between them. Using our 3-D models, we also investigate different antenna array configurations and their effect on the capacity of MIMO M-to-M systems. Contrary to common assumptions, we have found that there is no significant loss of capacity if the antenna array is tilted from the horizontal plane. Finally, we propose the design criteria for space-time coded continuous phase modulated systems. Our work would provide other researchers the tools needed to design and test future MIMO M-to-M communication systems.

Le travail présenté dans ce mémoire traite de l’étude comportementale, de la conception et de la validation d’une nouvelle architecture, basée sur le couplage d’O.C.T différentiels, appliquée à la commande électronique de l’orientation du diagramme de rayonnement d’un réseau d’antennes linéaire. Après avoir optimisé la structure de l’O.C.T différentiel, qui constitue le corps du circuit de commande, selon une méthode graphique qui visualise les différentes contraintes imposées par le système afin de minimiser son bruit de phase et sa consommation, l’O.C.T à sorties différentielles a été réalisé en technologie NXP BiCMOS SiGe 0,25 μm puis mesuré en boîtier. Etant donné que la direction de rayonnement d’une antenne réseau dépend de la valeur du déphasage imposé entre les signaux envoyés sur deux antennes adjacentes, les équations théoriques modélisant deux O.C.T couplés et permettant d’extraire les amplitudes et le déphasage entre les différents signaux ont été décrites. La dernière étape a alors consisté en la réalisation de deux réseaux constitués respectivement de deux et de quatre O.C.T couplés au moyen d’une résistance puis d’un transistor MOS fonctionnant en zone ohmique. L’approche de couplage proposée a été validée en se basant sur les résultats de mesures effectués. De plus, l’impact de l’utilisation de structures différentielles sur la plage de déphasage obtenue et donc sur le dépointage réalisé a également été présenté ce qui nous a permis de conclure sur l’efficacité du circuit de commande proposé. / The work presented in this thesis deals with the study, design, and validation of a new architecture based on the coupling of differential voltage controlled oscillators (VCO) applied to the beamsteering of a linear antenna array. After optimizing the differential VCO structure, with a graphical optimization approach while satisfying design constraints imposed, in order to minimize the phase noise and power consumption, the differential VCO was realized in NXP BiCMOS SiGe 0.25 µm process and then measured. Since the radiation direction of an antenna array depends on the phase difference imposed between the two signals on adjacent antennas, the theoretical equations modeling two coupled VCOs, and allowing the extraction of the amplitude and phase difference between the outputs signals have been presented. The last step was the realization of two arrays consisting respectively of two and four VCOs coupled through a resistor and a MOS transistor operating in the triode region. The proposed coupling approach is validated based on the obtained measurement results. Furthermore, the impact of the use of differential structures on the phase shift range obtained and thus on the beam-scanning range achieved was also presented allowing to conclude on the efficiency of the proposed architecture.

L'essor des communications par satellites et des nouvelles technologies de l'information et de la communication conduisent à une demande croissante de la part des utilisateurs. Ainsi, afin de répondre à ces nouveaux besoins, des services proposant de la connectivité en vol pour les passagers des compagnies aériennes voient le jour. Les travaux présentés dans ce mémoire portent sur la réalisation de modèles numériques rigoureux de grands réseaux d'antennes destinés à couvrir ce champ applicatif. Après une mise en contexte et un rappel des contraintes liées aux réseaux d'antennes, des véhicules de test numériques et expérimentaux, permettant de valider les méthodologies de modélisation, sont réalisés. La modélisation d'un grand panneau rayonnant à bipolarisation circulaire et acceptant d'importants angles de dépointage est enfin abordée. Cette étude permet alors de statuer sur les performances du panneau, en fonction des consignes de pointage et des dispersions éventuelles des chaînes actives. / The rapid expansion of satellite communications and information and communications technology led to an increasing demand from end-users. Hence, services offering In-Flight Connectivity for airlines passengers are emerging. This work is focused on the implementation of accurate numerical models of large antenna arrays meant for this scope. After having put things into context and recalled issues linked to antenna arrays, numerical and experimental test vehicles are made, allowing to validate the modelling methodologies. Finally, the modelling of a large, dual circular polarization and wide-angle scanning radiating panel is addressed. This study then allows to estimate the performance of the panel function of steering requirements and possible dispersions from the active channels.

Abstract In this doctoral thesis, initial code synchronization (i.e., code acquisition) of a direct sequence spread spectrum (DS/SS) system is studied when a smart antenna is used in a receiver. Code synchronization means time synchronization of the used spreading code in the receiver. After an introduction to the topic, a literature review of code acquisition is presented. In addition, a review of the results in the literature under fading, data modulation, Doppler, intentional interference, multiple-access interference, other system interference, and multiple antennas is given. After that, an overview of the smart antennas, especially focusing on digital beamforming and direction-of-arrival (DOA) estimation algorithms is presented. The end part of the thesis concentrates on the author’s own research of the topic. Original articles of this article dissertation have been classified according to their contents into two groups. The first group covers DS/SS code acquisition performance in intentional interference by exploiting how well different beamforming algorithms can eliminate narrowband and wideband interfering signals in the case, where the DOA of the desired signal is known. The obtained results show that most spatial beamforming algorithms are capable of cancelling multiple different types of interfering signals if they are not arriving from the same direction as the desired signal. If angle separation between desired and interfering signals is not sufficient, then more complex methods have to be used. The second group of articles focuses on a theoretical analysis of synchronization probabilities and mean acquisition times. If the DOA of the desired signal is unknown, the whole angular uncertainty region can be divided into small angular cells using beamforming techniques, as is proposed in the literature. Then there is a two-dimensional (delay-angle) acquisition problem. In this thesis, the research work of that area is expanded to cover also advanced beamforming techniques, since they offer increased interference suppression capability. It is shown that the code acquisition performance of the delay-angle method can be improved in some cases by adding a DOA estimator into the system, because it may reduce the number of required angular cells. In addition, such a minimum mean square error (MMSE) beamforming structure is proposed, where only one period of the known pseudo noise spreading code is used as a reference signal. The method was shown to have better acquisition performance than the delay-angle method has, since MMSE beamforming does not need DOA information. However, in this thesis, such a method was not found which outperforms the rest of the methods in all scenarios. / Tiivistelmä Tässä väitöstyössä tutkitaan suorahajotushajaspektrijärjestelmän (DS/SS, direct sequence spread spectrum) koodisynkronoinnin etsintävaihetta, kun vastaanottimessa käytetään älyantennia. Koodisynkronoinnilla tarkoitetaan järjestelmän käyttämän hajotuskoodin ajastuksen synkronointia vastaanottimessa. Johdannon jälkeen esitetään kirjallisuuskatsaus koodisynkronointiin sekä tuodaan esille kirjallisuudesta löytyviä tutkimustuloksia aihepiiristä seuraavissa tilanteissa: häipyvä kanava, Doppler-ilmiö, tahallinen häirintä, monikäyttöhäiriö, muiden järjestelmien aiheuttama häiriö sekä moniantennijärjestelmät. Tämän jälkeen esitetään yleiskatsaus älyantenneihin kohdistuen erityisesti digitaalisiin keilanmuodostus- sekä suuntaestimointialgoritmeihin. Työn loppuosa keskittyy kirjoittajan omaan tutkimukseen aiheesta. Tämän nippuväitöskirjan alkuperäiset artikkelit on luokiteltu kahteen ryhmään niiden sisältöön perustuen. Ensimmäinen ryhmä käsittelee DS/SS-järjestelmän koodisynkronoinnin etsintävaiheen suorituskykyä tahallisessa häirinnässä tutkimalla, miten hyvin erilaiset keilanmuodostusalgoritmit kykenevät poistamaan kapea- ja leveäkaistaisia häirintäsignaaleja tilanteessa, jossa hyötysignaalin tulosuunta tiedetään. Tutkimustulokset osoittavat, että monet tilatason keilanmuodostusalgoritmit kykenevät poistamaan useita erityyppisiä häirintäsignaaleita, jos ne eivät saavu hyötysignaalin kanssa samasta suunnasta. Mikäli kulmaero hyöty- ja häirintäsignaalien välillä ei ole riittävä, joudutaan käyttämään rakenteeltaan monimutkaisempia menetelmiä. Toinen ryhmä artikkeleita keskittyy synkronointiin liittyvien todennäköisyyksien ja keskimääräisen etsintäajan teoreettiseen analyysiin. Jos hyötysignaalin tulosuunta on tuntematon, voidaan kulmaepävarmuusalue jakaa pieniin kulmasoluihin käyttäen keilanmuodostustekniikoita, kuten kirjallisuudessa esitetään. Tällöin kyseessä on kaksiulotteinen (viive-kulma) etsintäongelma. Tässä työssä kyseistä tutkimusaihetta laajennetaan koskemaan myös edistyneet keilanmuodostusmenetelmät, koska ne tarjoavat parantuneen häiriönvaimennuskyvyn. Työssä osoitetaan, että viive-kulma menetelmän suorituskykyä voidaan parantaa joissakin tilanteissa lisäämällä järjestelmään suuntaestimaattori, koska se saattaa vähentää tarvittavien kulmasolujen lukumäärää. Lisäksi tutkitaan sellaista pienimmän keskineliövirheen (MMSE, minimum mean square error) keilanmuodostusmenetelmää, jossa ainoastaan yhtä hajotuskoodin koodijaksoa käytetään opetukseen. Kyseisellä menetelmällä todettiin olevan parempi suorituskyky kuin viive-kulma etsinnällä, koska MMSE-menetelmä ei tarvitse suuntainformaatiota. Tässä työssä ei kuitenkaan löydetty yhtä sellaista menetelmää, jonka suorituskyky on muita parempi kaikissa tilanteissa.

L'objectif de cette thèse est de trouver la forme optimale d'une antenne planaire ou d'un réseau d'antennes planaires à partir de contraintes imposées (diagramme de rayonnement, gain ou directivité) ou de reconstruire la forme à partir de mesures expérimentales. L'algorithme d'optimisation développé est basé sur une méthode de type gradient et la reconstruction des contours par une méthode d'ensembles de niveaux (Level Sets) ou "contours actifs". Le problème direct est résolu en utilisant une formulation intégrale du problème électromagnétique et une méthode d'éléments finis pour la discrétisation. Le gradient de forme est calculé en utilisant deux méthodes différentes. Tout d'abord, une méthode par différences finies basée sur la dérivée à un nœud du maillage, pour une modification infinitésimale des éléments triangulaires du contour, suivant la direction de la normale extérieure. La deuxième méthode est basée sur le gradient topologique pour le calcul de la déformation des contours. Une méthode d'ensembles de niveaux avec bande étroite a été développée pour faire évoluer le contour des antennes utilisant la vitesse de déformation calculée à partir du gradient de forme. Différentes configurations d'antennes et réseaux d'antennes planaires ont été utilisées pour étudier les performances de l'algorithme d'optimisation. Des techniques de type saut de fréquence et multifréquence ont été utilisées pour optimiser la forme dans une bande de fréquence. L'optimisation de forme pour la miniaturisation d'antennes planaires concerne de nombreuses applications, en particulier, pour les réseaux réflecteurs / The objective of this thesis work is to find the optimal shape of planar antenna elements and arrays from imposed constraints (e.g. desired or imposed radiation patterns, gain or directivity) or to reconstruct the shape from experimental measurements. The optimization algorithm is based on the gradient-type method and an active contour reconstruction by means of the Level Set method. The forward problem is solved using an integral formulation of the EM problem with finite element discretization. The shape gradient is computed using two different methods: one is finite differential method based on nodal point mesh derivation with an infinitesimal modification of the triangular elements on the contour along the outward normal direction, another the topological shape gradient, which is computed based on a topological deformation on a contour. A narrow band level set method has been developed to evolve the contour of antennas and arrays using the deformation velocity computed from the shape gradient. Different configurations of antennas and antenna arrays are studied for investigating the performance of the optimization algorithm. Frequency hopping and multi-frequency techniques have been used for optimizing the shape within a frequency band. Shape optimization for planar antenna miniaturization has a large number of applications, particularly, for reflectarrays

Un radar MIMO (Multiple Input Multiple Output) est un système radar qui utilise plusieurs antennes émettrices et réceptrices, dans lequel les formes d'ondes émises peuvent être indépendantes. Par rapport aux radars utilisant des antennes en réseaux phasés, les radars MIMO offrent davantage de degrés de liberté, ce qui permet d'améliorer les performances du système en termes de détection et localisation. La technique MIMO offre également la possibilité de synthétiser un diagramme de rayonnement désiré par une définition judicieuse des formes d'ondes émises. Dans la mesure où les paramètres des cibles (positions, vitesses, directions d'arrivée (DOA), ...) sont estimés à partir des échos des signaux émis, on comprend aisément que les formes d'ondes employées jouent un rôle clé dans les performances du système. Cette thèse porte sur l'estimation de DOA et sur la conception des formes d'ondes pour un radar MIMO. Le cadre d'étude est restreint au cas où les antennes sont colocalisées et les cibles sont immobiles et supposées ponctuelles. La plupart des travaux antérieurs (au commencement de la thèse) portaient sur le radar MIMO bande étroite et faisaient l'hypothèse d'émetteurs-récepteurs idéaux et indépendants. Cette thèse contribue à élargir le cadre d'étude en s'intéressant d'une part au passage en large bande et d'autre part à la modélisation et à la prise en compte de la non-indépendance des émetteurs-récepteurs et autres imperfections. Dans la mesure où le recours à des signaux large bande est nécessaire lorsqu'une résolution importante est souhaitée, nous nous sommes attachés dans cette thèse à adapter le modèle d'un système de radar MIMO au cas large bande et à proposer de nouvelles techniques visant à améliorer les performances d'estimation de DOA dans le cas de signaux large bande. Cette thèse analyse également l'influence de conditions non idéales comme l'impact des phénomènes de couplage électromagnétique sur les diagrammes de rayonnement dans un réseau d'antennes. Cette étude est menée dans le cas bande étroite. En particulier, nous étudions l'influence du couplage direct entre les réseaux d'antennes d'émission et de réception (appelé « crosstalk ») sur les performances des techniques proposées. Nous établissons un modèle du signal permettant de prendre en compte ce phénomène et proposons une technique de réduction du « crosstalk » qui permet une estimation efficace des DOA des cibles. Nous montrons par ailleurs comment améliorer les performances d'estimation de DOA en présence de diagrammes de rayonnement incluant le couplage entre antennes. Le dernier apport principal de cette thèse est la conception et réalisation d'une plateforme expérimentale comportant une seule architecture d'émetteur-récepteur, qui permet de simuler un système MIMO utilisant des antennes colocalisées en appliquant le principe de superposition. Cette plateforme nous a permis d'évaluer les performances des techniques proposées dans des conditions plus réalistes / A Multiple-Input Multiple-Output (MIMO) radar is a system employing multiple transmitters and receivers in which the waveforms to be transmitted can be totally independent. Compared to standard phased-array radar systems, MIMO radars offer more degrees of freedom which leads to improved angular resolution and parameter identifiability, and provides more flexibility for transmit beampattern design. The main issues of interest in the context of MIMO radar are the estimation of several target parameters (which include range, Doppler, and Direction-of-Arrival (DOA), among others). Since the information on the targets is obtained from the echoes of the transmitted signals, it is straightforward that the design of the waveforms plays an important role in the system accuracy. This document addresses the investigation of DOA estimation of non-moving targets and waveform design techniques for MIMO radar with colocated antennas. Although narrowband MIMO radars have been deeply studied in the literature, the existing DOA estimation techniques have been usually proposed and analyzed from a theoretical point of view, often assuming ideal conditions. This thesis analyzes existing signal processing algorithms and proposes new ones in order to improve the DOA estimation performance in the case of narrowband and wideband signals. The proposed techniques are studied under ideal and non-ideal conditions considering punctual targets. Additionally, we study the influence of mutual coupling on the performance of the proposed techniques and we establish a more realistic signal model which takes this phenomenon into account. We then show how to improve the DOA estimation performance in the presence of distorted radiation patterns and we propose a crosstalk reduction technique, which makes possible an efficient estimation of the target DOAs. Finally, we present an experimental platform for MIMO radar with colocated antennas which has been developed in order to evaluate the performance of the proposed techniques under more realistic conditions. The proposed platform, which employs only one transmitter and one receiver architectures, relies on the superposition principle to simulate a real MIMO system

Indiana University-Purdue University Indianapolis (IUPUI) / This thesis proposes a reconfigurable phased array of antennas for wireless power transfer. The array finds use in many applications, from drone destruction (for defense) to wireless charging of robots and mobile devices. It utilizes a novel feeding architecture to greatly reduce the number of high cost elements (such as amplifiers and phase shifters) as well as the quantity of unused resources in the system. Upon the instruction of the CPU, the array can separate into any number of subarrays, each of which transmits power to a single receiver, steering its beam as the receiver changes location. Currently dormant elements in the array can be used to provide position information about the receivers, either via Radar, or by listening for beacons pulses from the receiver. All of this is made possible, with only 4 amplifiers and 3 phase shifters, by the proposed 4-Bus Method. The source signal is divided into four buses, which are respectively phase shifted by 270 degrees, 180 degrees, 90 degrees, and 0 degrees (no shifter required) and then amplified. The CPU calculates, based on the number and positions of the receivers / targets, what the amplitude and phase excitation must be at each element. Any phase and amplitude which could be required can be achieved by simply adding together appropriate quantities of the correct two buses. In order to achieve this, the key piece is the variable power divider. These differ from Wilkinson dividers in that the dividing ratio can be changed via an applied DC voltage. Therefore, at each junction, by properly diverting the power levels on each phase bus to their proper location, complete delocalization of both amplifiers and phase shifters can be achieved. A method has also been developed which helps overcome the limitations of each variable power divider. That is, in certain instances, it may be desirable to pass all the power to a single output port or the other, which is not a possibility inherently possible with the device. With the use of a unique combination of RF switches, the nodes achieve much enhanced flexibility. Finally, an intensive study is carried out, in an attempt to yield greater understanding, as well as quick, useful approximations, of the behaviors of both rectangular and hexagonal arrays of various sizes and beam steering angles for wireless power.