The need for a wide bandwidth array is introduced and explained. Basic planar array principles are reviewed as well as previous work performed on wide bandwidth planar array design. An Archimedean spiral is suggested for the array element and a model for the element radiation pattern is presented. A wide bandwidth linear array is then analyzed using the element model. The array is made to operate over a two octave bandwidth by using an alternate number of elements. This idea is then extended to two dimensions to form a wide bandwidth planar array design. An improved array design is then suggested using fewer elements. This array was fabricated and tested and showed close agreement to theoretically predicted radiation patterns. / M.S.

One of the important considerations in radio link analysis is the signal degradation that accompanies rainfall in a link’s path. Random scattering by rain can adversely affect a propagating wave in two ways. First, it results in attenuation and depolarization of the coherent field which is associated with the forward propagating wave. ln addition to this, random scattering gives rise to an incoherent field component that can further degrade the signal in a manner similar to multipath. This dissertation presents an analysis of the coherent and incoherent effects of rain scatter at millimeter-wave frequencies. Within it, the scattering properties of individual spherical and non-spherical are quantified. Spherical raindrops are treated using the Mie theory and non-spherical ones analyzed with Waterman’s Extended Boundary Condition Method. Computed values of forward scattering amplitudes and scattering cross-sections for both spherical and non-spherical raindrops at 80, 45, 70 and 90 GHz are presented; the computer programs used to obtain the scattering data are also provided. Following the analysis of individual raindrops scatterers, the Foldy·Lax Twersky integral equations for coherent field and incoherent intensity are used to derive the coherent and incoherent outputs of a generic radio receiver. In doing so, the effects of scattering in an antenna’s far-field and radiating near field (Fresnel Region) are analyzed. Through this analysis, it is shown that the expected system outputs are essentially the same in either case. Using the computed raindrop scattering parameters and models developed for the coherent and Incoherent system outputs, specific cases are Iooked at for 30, 45, 70 and 90 GHz operation and theoretical data presented. The data consists of the predicted attenuation and Isolation of the coherent signal and the ratio of coherent to Incoherent power In the presence of rain. From the latter it Is found that during heavy rainfall, the Incoherent effects can be appreciable and should be taken into account. / Ph. D.

High resolution earth observation from geostationary orbit offers several advantages compared to traditional low earth orbit systems. Among the advantages are decreased time to scan the visible geo-disk and the ability to stare at a particular event. The following work is concerned with the design of a reflector antenna configuration for passive remote sensing and suitable for use on a geostationary platform; however, the resultant configuration is not limited to this application. The specific goal is the design of a reflector antenna configuration capable of precision beam scanning over a range of several degrees in all directions while minimizing vibration and inertial torque such as to have minimal effect on the other instruments sharing the platform. Desirable characteristics of such a reflector configuration are: a stationary feed consisting of a single element or a small array; simple reflector motions; and high primary aperture utilization for all scan directions (high illumination efficiency). This dissertation documents the development of a novel tri-reflector antenna configuration which addresses the design goals outlined above. The reflector configuration has been named the conjugate tri-reflector. The conjugate tri-reflector consists of a parabolic primary reflector an elliptical secondary reflector and a shaped tertiary reflector. Beam scanning is performed entirely by motion of the relatively small tertiary reflector. The proposed reflector configuration offers substantial improvement in scan performance compared to that achieved by feed displacement with a prime focus parabolic reflector and has a much higher aperture efficiency than comparable spherical reflector configurations. / Ph. D.

Orientador: Michel Daoud Yacoub / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-27T01:29:54Z (GMT). No. of bitstreams: 1 Barbin_ManoelVitorio_M.pdf: 5394528 bytes, checksum: f2e1dbef898be5580589baf0e2996f16 (MD5) Previous issue date: 2015 / Resumo: A identificação de objetos através de ondas de radiofrequência ou RFID (Radio Frequency Identification) é uma tecnologia onde uma etiqueta, colocada em um objeto, tem suas informações lidas por um sistema de processamento remoto. Embora esta não seja uma tecnologia recente, sua utilização tem apresentado constante crescimento nos últimos anos. Atualmente, RFID é apontada com uma das principais tecnologias habilitadoras da internet do futuro, a Internet das Coisas, IoT (Internet of Things). Operando principalmente em faixas destinadas para o uso de aplicações médicas, científicas e industriais, ISM (Industrial, Scientific and Medical), sistemas de RFID apresentam diferentes características em função da banda de frequências utilizada. Em UHF (Ultra High Frequency), os sistemas de RFID que fazem uso de etiquetas passivas, são considerados como uma solução com bom desempenho para a identificação de objetos em distâncias que variam de alguns poucos centímetros a vários metros. Contudo, a distância de identificação depende do material que constitui um dado objeto. Por exemplo, metais estão entre os materiais que degradam significativamente o desempenho de sistemas de RFID em UHF, reduzindo a distância de identificação. Diversas soluções de etiquetas têm sido desenvolvidas com o objetivo de torná-las, o máximo possível, insensíveis à presença do metal. Alguns diferentes tipos de antenas foram propostas, entre as quais se destacam as que possuem um plano-terra inerente a sua estrutura, como a de microfita e a planar de F-Invertido, PIFA (Planar Inverted-F Antenna). Uma revisão destas soluções é realizada nesta dissertação. Este trabalho descreve o projeto de uma etiqueta passiva de RFID em UHF, baseado em uma PIFA, para identificação de objetos metálicos colocados em distâncias maiores que oito metros, aproximadamente. O principal objetivo de uso da etiqueta é na identificação de objetos com razoáveis dimensões tais como containers, chapas, canos, etc., frequentemente encontrados em ambientes industriais e armazéns de estocagem. Uma forma diferente de alimentação do sinal de radiofrequência para a antena é desenvolvida. Simulações eletromagnéticas e medições indicam um bom desempenho da etiqueta em uma ampla faixa de frequências, que abrange as principais bandas de operação de RFID em UHF no mundo / Abstract: The identification of objects by radio waves or RFID (Radio Frequency Identification) is a technology where a tag is attached to an object and its information read by a remote processing system. Although it is not a new technology, its use has shown steady growth in recent years. Currently, RFID is identified as one of the main enabling technologies of the future Internet, the Internet of Things, IoT. Operating in the bands intended primarily for use in industrial, scientific and medical (ISM) applications, RFID systems have different characteristics depending on the frequency band used. In the UHF (Ultra High Frequency) band, RFID systems using passive tag are considered as a solution with good performance to identify objects at distances ranging from a few centimeters to several meters. However, the distance of identification depends on the material that the object is made of. For example, metals are materials which can significantly degrade the performance of UHF RFID systems by reducing the distance of identification. Several solutions for tags have been developed in order to make them, as far as possible, insensitive to the presence of metal. Some different types of antennas were proposed, among which are those with a ground plane inherent in its structure, such as the microstrip antenna and the PIFA (Planar Inverted-F Antenna). A review of these solutions is carried out in this dissertation. This document describes the design of a passive RFID tag in UHF, based on a PIFA for identification of metallic objects placed at distances greater than eight meters or so. The main use of the tag is to identify objects with medium or large dimensions such as containers, plates, pipes, etc., often found in industrial environments and storage warehouses. A different kind of RF feeder to the antenna is developed. Electromagnetic simulations and measurements indicate a good tag performance in a wide frequency band, which covers the main RFID UHF operation bands in the world / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

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

Approved for public release, distribution is unlimited / This thesis is a continuation of the design and development of a three-dimensional 2.4 GHz digital phased array radar antenna. A commercial off-the-shelf quadrature modulator and demodulator were used as phase shifters in the digital transmit and receive arrays. The phase response characteristic of the demodulator was measured and the results show that the phase difference between the received phase and transmit phase is small. In order to increase the bandwidth of the phased array, a method of time-varying phase weights for linear frequency modulated signal was investigated. Using time-varying phase weights on transmit and receive give the best performance, but require the range information of the target. It is more practical to use time-varying phase weights on only one side (transmit or receive but not both), and constant phase weights on the other side. The simulation results showed that by using time-varying phase weights, the matched filter loss is not as severe as it is when using the conventional fixed weights technique. It was also found that this method is only effective for small scan angles when the time-bandwidth product is large. The approach to implement time-varying phase weights on transmit using commercial components such as direct digital synthesizer and quadrature modulator is discussed. / Civilian, Ministry of Defense, Singapore

A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering, 2017 / In the mining industry, communications systems are important for ensuring personnel safety and optimizing the mining processes underground. Achieving robust and reliable through-the-air (TTA) communication systems has always been a challenge in the underground mining environment due to harsh and dynamic conditions. TTA requires radio channel characterization for efficient designing and deploying of the communications systems. The literature covers the statistical radio propagation of a room and pillar coal mine, a longwall coal mine, CANMET Gold mine, Camborne School of Mines hard rock mine tunnel, MUZ Coal mine, an iron-ore mine and a lead-zinc mine with linearly polarized antennas at different frequencies. [Abbreviated Abstract. Open document to view full version] / MT 2017

Avec l'augmentation du trafic de données, la multiplication des objets connectés et la diversification des types de communication, la cinquième génération de réseaux cellulaires (5G) doit relever un grand nombre de défis. Dans ce contexte, les systèmes« massive MIMO » présentent de nombreux avantages en utilisant un grand nombre d'antennes combiné à des techniques de traitement de signal adaptées. De plus, l'utilisation de la modulation FBMC/OQAM au lieu de la modulation OFDM pourrait améliorer la performance des systèmes dans ce11aines situations. En premier lieu, cette thèse se centre sur des scénarios véhiculaires. En par1iculier, les systèmes« massive MIMO » sont proposés dans le but de combattre les interférences dues à l'effet Doppler pour la voie montante. Nous montrons ainsi de manière analytique que l'augmentation du nombre d'antennes implique une réduction drastique de l'impact de l'effet Doppler. De plus, les performances des modulations OFDM et FBMC/OQAM sont comparées dans ce contexte pour des environnements« Non-Line-Of-Sight » (NLOS) et« Line-Of-Sight » (LOS). Le second scéna1io étudié dans cette thèse considère les communications dans des zones mal desservies. Dans ce contexte, les systèmes« massive MIMO » permettent de créer un lien sans-fil longue-po11ée de type« backhaul » entre deux stations de base. Ainsi, le coût de déploiement des réseaux r cellulaires est réduit. Dans cette thèse, un nouveau précodeur « massive MIMO » est proposé dans le but d'utiliser la même bande de fréquence pour le liens accès et« backhaul ». De plus, l'impact d'une désynchronisation entre les liens d'accès et le lien « backhaul » est étudié et l'utilisation de la modulation FBMC/OQAM pour le lien« backhaul » est examinée. / ESUME DE LA THESE EN ANGLAIS With the increase of the global data tmffic, the multiplication of co1mected devices and the diversification of the communication types, the fifth generation of cellular networks (5G) has to overcome a se1ies of challenges. In this context, massive MlMO systems hold a wide range of benefits by using a large number of antennas combined with appropriate signal processing techniques. Additionally, the use of the FBMC/OQAM modulation instead of the classical OFDM modulation may enhance the performance of the systems in cer1ain situations. Firstly, this thesis focuses on vehicular scenarios. In par1icular, massive MIMO systems are proposed to overcome the interference due to the Doppler effect for the uplink. We thus analytically highlight that increasing the number of receive antermas induces a drastic reduction of the impact of the Doppler effect. Moreover, the perfonnance of the OFDM and the FBMC/OQAM modulations are compared in this context for Non-Line-Of-Sight (NLOS) and Line-Of-Sight (LOS) environments. The second scenario investigated in this thesis considers communications in wide underse1ved areas. In this context, massive MIMO systems allow to create a long-range wireless back.haul link between two base stations. Thereby, the cost of deployment of the cellular networks is reduced. In this thesis r a new massive MLMO precoding technique is proposed in order to use the same fequency band for the backhaul link and the access links. Moreover, the impact of a desynchronization between the back haul link and the access links is studied and the use of the FBMC/OQAM modulation for the backhaul link is discussed.

In a MIMO system, a transmitter with perfect knowledge of the underlying channel state information (CSI) can achieve a higher channel capacity compared to transmission without CSI. When reciprocity of the wireless channel does not hold, the identification and utilization of partial CSI at the transmitter are important issues. This thesis is focused on partial CSI acquisition and utilization techniques for MIMO channels. We propose a feedback algorithm for tracking the dominant channel subspaces for MIMO systems in a continuously time-varying environment. We exploit the correlation between channel states of adjacent time instants and quantize the variation of channel states. Specifically, we model a subspace as one point in a Grassmann manifold, treat the variations in principal right singular subspaces of the channel matrices as a piecewise-geodesic process in the Grassmann manifold, and quantize the velocity matrix of the geodesic. We design a complexity-constrained MIMO OFDM system where the transmitter has knowledge of channel correlations. The transmitter is constrained to perform at most one inverse Discrete Fourier Transform per OFDM symbol on the average. We show that in the MISO case, time domain beamforming can be used to do two-dimensional eigen-beamforming. For the MIMO case, we derive design criteria for the transmitter beamforming and receiver combining weighting vectors and show some suboptimal solutions. The feedback channel may have uncertainties such as unexpected delay or error. We consider channel mean feedback with an unknown delay and propose a broadcast approach that is able to adapt to the quality of the feedback. Having considered CSI feedback problems where the receiver tries to convey its attained CSI to the transmitter, we turn to noncoherent coding design for fast fading channels, where the receiver does not have reliable CSI. We propose a data-dependent superimposed training scheme to improve the performance of training based codes. The transmitter is equipped with multiple training sequences and dynamically selects a training sequence for each data sequence to minimize channel estimation error. The set of training sequences are optimized to minimize pairwise error probability between codewords.

Array antennas are used extensively in remote sensing applications, where a highly directive beam is needed to scan a particular area of interest on the surface of the earth. The research presented here focuses on the design of different microstrip patch antenna arrays to be used in environmental sensing applications in the X and Ka frequency bands, such as measurements in Snow and Cold Land Processes (SCLP) to detect snow accumulation, snow melt, etc. The goal of this research is to produce highly integrated, low loss, and compact size antenna arrays, while maintaining low power consumption. Multilayer organic (MLO) System-on-a-Package (SOP) technology, using laminates such as Liquid Crystal Polymer (LCP) and RT/Duroid®, provides a lightweight and low cost 3D solution for the fabrication of the antenna arrays. The elements of the antenna arrays are rectangular patches. Two feeding mechanisms, aperture coupling and via feed, were implemented and compared. For the RF distribution network and interconnects, a corporate feed approach was used with reactive T-junctions, Wilkinson dividers, or both, for power division. The feed networks were designed using microstrip. The basic multilayer antenna array design consists of 3 layers of cladded laminate material. The metal layers are as follows: 1) patch antennas, 2) ground plane, 3) feed network, and 4) surface-mount components. The surface mount components would include LNA, PA, TR switch and phase shifter.