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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

In-Flight Auto-Tune of an Airborne Synthetic Beamforming Antenna

Lamarra, Norm, Kelkar, Anand, Vaughan, Thomas 10 1900 (has links)
ITC/USA 2011 Conference Proceedings / The Forty-Seventh Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2011 / Bally's Las Vegas, Las Vegas, Nevada / At ITC 2009, we described the real-world complications of fielding an airborne Synthetic beamforming Telemetry System, which simultaneously supports 20 individual beams (10 at each of 2 polarizations). We described how our layered Open-Source software approach helped us to modify the system rapidly after delivery without disrupting mission operations. Since then, we have further extended the software toolset that we developed to dissect the System behavior via post-mission replay and analysis, and to compare high-resolution in-flight measurements with our detailed physics simulations. This analysis has shown that the most significant factor affecting operational performance of the System was variation in the relative phase of the elements from day to day. These variations were traced to a variety of hardware issues, none of which could be resolved without major cost and effort. As an alternative approach, we developed a dynamic auto-tuning capability that optimizes the phase calibration of the System using each actual signal source as it is being tracked. This results in improved signal-to-noise performance while reducing the need for dedicated in-air calibration flights that we had previously created. We believe that the flexibility of digital beamforming, allied with a modular and easily-extensible software architecture, have again proven capable of quickly and cheaply mitigating real-world operational issues, without (so far) requiring any hardware modification of the delivered System.
2

Projeto e desenvolvimento de um sistema inteligente para alinhamento de uma antena parabólica receptora

Marcos César Rafael 25 November 2011 (has links)
O objetivo deste trabalho é projetar e desenvolver um sistema automatizado inteligente para o alinhamento de uma antena receptora com refletor parabólico aplicado a comunicação via satélite. Com base em procedimentos empíricos para o alinhamento manual de uma antena parabólica, foi concebida e desenvolvida uma solução tecnológica empregando hardware e software. O sistema concebido utiliza um GPS, para prover a localização espacial instantânea da antena receptora e um receptor digital, que fornece a relação portadora / ruído de recepção. A principal contribuição deste trabalho foi o projeto e desenvolvimento de um sistema computacional inteligente, denominado Sistema Inteligente de Alinhamento de Satélite que visa a automatizar o alinhamento de antena receptora. Para um determinado satélite, o sistema utiliza a informação sobre a qualidade do sinal recebido para acionar um servomecanismo responsável pelo alinhamento da antena. Verificou-se que quando a antena estiver na posição desejada, a relação portadora ruído deverá estar acima de 8 dB para uma boa qualidade de recepção. Foi desenvolvido um projeto de um sistema inteligente para uma varredura em torno do valor de referência de posição da antena, o qual se denominou ajuste fino da posição da antena. Nossa inédita abordagem para o ajuste fino projetou-se um controlador fuzzy do tipo Mandani, cujas regras foram geradas de acordo com o processo de posicionamento manual da antena parabólica. Nossa solução permitiu melhorar a relação portadora / ruído de recepção. / The objective of this work is to design and develop an intelligent automated system for the alignment of a receiving antenna with parabolic reflector applied to satellite communication. Based on empirical procedures manual for the manual alignment of a parabolic antenna, we designed and developed a technological solution using hardware and software. The system uses a GPS to provide the initial spatial location of the receiving antenna and a digital receiver to provide the carrier-to-noise ratio. The main contribution of this work was the design and development of an intelligent computational system which aims at automating the receiving antenna alignment. For a given satellite, through the dynamic handling of relocate the receiving antenna, the system uses information about the quality of the received signal to drive the servo responsible for aligning the antenna. We found that, the antenna is in the desired position, the carrier-to-noise ratio should be above 8 dB for a good reception quality. We developed the project of an intelligent system to scan around the reference antenna position value, which was called the antenna position fine tuning. Our new approach consisted in a fuzzy controller type Mandani, generated according to the manual process of maneuvering the dish. Our solution has improved the carrier-to-noise ratio by repositioning the antenna in the desired position.

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