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Design, modeling and control of a SATCOM on-the-move antenna terminal

Karaçal, İlim
The world becomes more connected with the help of increasing two-way communication day by day. High bandwidth data downlink demand independent of the range has increased excessively over the years. Also, communication need in all types of terrain conditions introduced a new communication method. Therefore, SATCOM on the move terminals become an important way of communication. These terminals provide to access communication in any environment and even at host vehicles. High disturbance rejection demand, compact design requirements and cost-effective solutions make the antenna system design challenges. Because to reach high data transmission rates antenna should be pointed with high precision. There exists tracking algorithms to increase the pointing performance of an antenna without the need for complex and costly hardware solutions. These dedicated tracking algorithms use the received signals from the target source as feedback to track the target all the time. This thesis focuses on design, modeling and control of a SATCOM on the move antenna gimbal system for maritime application. ASELSAN antenna gimbal terminal is used. This system is used in ship platforms for data communication. In this study, firstly antenna system architecture, components, gimbal design criteria and principles of operations are defined. System identification tests are performed to obtain system behavior under different conditions. Then, the mathematical model of the gimbal is obtained and the gyro-stabilized control-loop is designed to perform required performance metrics. Open and closed-loop pointing strategies are explained, implemented and simulated. Two closed-loop pointing methods are studied and their performances are analyzed. These are conical scanning and step tracking methods. The results of the studies are showed that inertial stabilization is crucial in LOS pointing performance. However, stabilization is not enough alone to provide required pointing accuracy and tracking methods should be used. Communication is lost in simulations with only LOS stabilization. However, tracking methods are provided to continue communication with oscillation in performance but it is still good enough even for the harsh simulation scenarios. It is obtained that conical scanning is more reliable and robust than step tracking technique. It is shown that uninterrupted high-bandwidth communication performance is possible with tracking methods.