In this thesis work, minimization of platform-based coupling between the antennas of two VHF radios on an aircraft platform and two HF radios on a ship platform is aimed. For this purpose / an optimal antenna placement, which yields minimum average coupling between the antennas over the whole frequency band of operation is determined for each platform. Two important global optimization techniques, namely Genetic Algorithm Optimization and Particle Swarm Optimization, are used in determination of these optimal antenna placements. Aircraft &amp / ship platforms and antennas placed on them are modeled based on their real electrical and physical properties in CST &ndash / MWS (Microwave Studio) simulation tool. For each platform, antenna placements and coupling results determined by two different optimization techniques and performances of these optimization techniques are compared with each other. At the end of this thesis work / for each platform, far-field radiation pattern performances of the antennas at their optimal places are analyzed in terms of directivity and coverage.

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The aim of this thesis is to improve the operational performance of the communication antennas mounted on complex platforms such as aircrafts and warships by arranging placements of these antennas. Towards this aim, primarily, in order to gain insight on the influence of geometrically simple structures composing the platform on antenna performance, a quarter wavelength monopole antenna placed at the center of a finite square ground plane is studied by using uniform Geometrical Theory of Diffraction (GTD). Besides, the change of far field radiation pattern and complex diffraction functions due to the variation of the width of a square ground plane is examined. Secondly, electromagnetic analysis of two Ultra High Frequency (UHF) antennas mounted on geometrically simple structures composing simplified F-4 aircraft is carried out by using transient solver of Computer Simulation Technology (CST) Microwave Studio&reg / (MWS), in order to conceive the influence of each structure on antenna performance. Then, electromagnetic analysis of these antennas mounted on simplified and original F-4 aircrafts is performed, in order to determine the optimal location of the lower UHF antenna (newly installed antenna) for the operational performance of this antenna to be optimum in terms of electromagnetic coupling and far field radiation pattern. Finally, electromagnetic analysis of the communication antennas mounted on a warship is performed by using transient solver of CST MWS&reg / , in order to determine the optimal locations of these antennas for the operational performance of these antennas to be optimum in terms of electromagnetic coupling and far field radiation pattern.

While the capacity of multiple-input multiple-output (MIMO) systems has been explored in considerable detail, virtually all literature on this topic ignores electromagnetic considerations. This dissertation explores electromagnetic effects on the capacity performance of these multi-antenna architectures. Specifically, it examines the impact of superdirectivity for compact antenna arrays, the effect of antenna mutual coupling, and MIMO performance of multi-mode optical fiber with non-linear detection. Superdirectivity can lead to abnormally large capacity bounds in a MIMO communication system, especially when the antennas are placed close together. Because superdirective behavior is difficult to achieve in practice, this work formulates an approach for limiting the impact of superdirectivity by introducing finite ohmic loss into the capacity expressions. Results show that even a small amount of ohmic loss significantly affects the achievable system capacity and suppresses superdirective solutions. This formulation allows a more detailed examination of the capacity of MIMO systems for compact arrays. For channels which do not vary in time, placing antennas closer together generally reduces the system capacity. However, recent work has demonstrated that for a MIMO system operating in a fast fading environment where the transmitter and receiver know the channel covariance information, the capacity increases as antennas are placed near each other due to an increase in spatial correlation. Analysis of this behavior illustrates that when these capacity gains (due to closely spaced antennas) are observed the radiated power is also increased. Constraining the radiated power leads to superdirective solutions in which the ohmic loss constraint developed must be used to properly determine the capacity behavior of this system. Application of this constraint then leads to an optimum antenna spacing in contrast to the findings of previous research which indicate that antennas should be as close together as possible. Additionally, this section provides an analysis regarding the number of spatial modes that can be used for various system configurations. Recent research has shown that it is possible for MIMO communication techniques to be used with multimode optical fibers to increase the available distance-bandwidth. However, implementation of traditional MIMO schemes requires the use of coherent optical detection which can lead to high system complexity and cost. This dissertation proposes a multimode fiber MIMO system architecture which allows simultaneous transmission of unique streams to different users on the same fiber while using incoherent detection with amplitude and phase modulation at the transmitter. The resulting capacity scales nearly linearly with the number of transmitters and receivers. Because the architecture requires channel state information at the transmitter, a training scheme appropriate for use with optical intensity detection is also discussed.

Future mines will benefit from connected intelligent transport system technologies. Autonomous mining vehicles will improve safety and productivity while decreasing the fuel consumption. Hence, it is necessary for Scania to increase the know-how regarding the design of vehicular communication systems for the harsh mine environment. The scope of this work is to examine the requirements for the antenna placement of a future autonomous mining truck and propose suitable antenna types and positions. By using the electromagnetic simulator suite CST Microwave Studio, the research estimates the impact of a simplified autonomous mining vehicle geometry on basic antenna radiation patterns. Some simulated antenna configurations are assessed with radiation pattern measurements. In order to radiate enough power towards the area surrounding the vehicle and guarantee reliable communications, the truck requires omnidirectional antennas in centered locations, or alternatively one patch antenna for each side. The method used to solve the problem is also assessed: flexibility provided by the simulation method is emphasized, whereas some relevant limitations are discussed. Hardware requirements, availability of the models and limited results provided by the software can make the simulation phase not suitable to evaluate the antenna placement. / Framtidens gruvor kommer att gynnas av sammankopplade, intelligenta transportsystem. Autonoma gruvfordon kommer att förbättra säkerhet och produktivitet, och samtidigt minska bränslekonsumtion. Därför är det nödvändigt för Scania att öka kunskapen om design av kommunikationssystem för fordon i hård gruvmiljö. Målet för detta projekt är att undersöka kraven för antennplacering hos ett framtida autonomt gruvfordon och att ge förslag på passande antenntyper och -positioner. Det elektromagnetiska simuleringsverktyget CST Microwave Studio används för att uppskatta påverkan från en förenklad fordonsgeometri på grundläggande antennstrålningsmönster. Utvalda antennkonfigurationer utvärderas genom undersökningar av dess strålningsmönster. För att kunna stråla ut tillräcklig effekt i området kring fordonet och garantera tillförlitlig kommunikation krävs centralt placerade runtstrålande antenner, eller alternativt en patchantenn till varje sida. Problemlösningsmetoden utvärderas också: Flexibiliteten simuleringsmetoden ger betonas, medan några relevanta begränsningar diskuteras. Hårdvarukrav, tillgängligheten av modeller och begränsade resultat från mjukvaran kan bidra till att göra simuleringen olämplig för att utvärdera antennplaceringen.