Browsing by Author "Rzasa, John"
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Item Design and Application of Pan and Tilt Servo Gimbals in Pointing, Acquisition, and Tracking(2007-12-07) Rzasa, John; Davis, Christopher C; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Directional wireless communications systems are fast becoming an essential part of the world's broadband network infrastructure. When using these types of transceivers in reconfigurable networks, it becomes necessary to point them rapidly and accurately to different locations, or even to targets that may be in motion. The most efficient way of doing this is through the use of two-axis pan and tilt motion stages, also known as gimbals. This paper presents the motivation for, design and construction of, and testing of a pair of multipurpose servo gimbals, usable for both RF and laser transceivers. The gimbals are tested in terms of pointing error, movement speed, and response time. For the network portion, relink times as a function of angular rotation are examined, as well as the angular offset vs. data rate. The gimbal is also tested as part of a remote surveillance network, evaluating its ability to track moving objects.Item POINTING, ACQUISITION, AND TRACKING FOR DIRECTIONAL WIRELESS COMMUNICATIONS NETWORKS(2012) Rzasa, John; Davis, Christopher C; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Directional wireless communications networks (DWNs) are expected to become a workhorse of the military, as they provide great network capacity in hostile areas where omnidirectional RF systems can put their users in harm's way. These networks will also be able to adapt to new missions, change topologies, use different communications technologies, yet still reliably serve all their terminal users. DWNs also have the potential to greatly expand the capacity of civilian and commercial wireless communication. The inherently narrow beams present in these types of systems require a means of steering them, acquiring the links, and tracking to maintain connectivity. This area of technological challenges encompasses all the issues of pointing, acquisition, and tracking (PAT). iii The two main technologies for DWNs are Free-Space Optical (FSO) and millimeter wave RF (mmW). FSO offers tremendous bandwidths, long ranges, and uses existing fiber-based technologies. However, it suffers from severe turbulence effects when passing through long (>kms) atmospheric paths, and can be severely affected by obscuration. MmW systems do not suffer from atmospheric effects nearly as much, use much more sensitive coherent receivers, and have wider beam divergences allowing for easier pointing. They do, however, suffer from a lack of available small-sized power amplifiers, complicated RF infrastructure that must be steered with a platform, and the requirement that all acquisition and tracking be done with the data beam, as opposed to FSO which uses a beacon laser for acquisition and a fast steering mirror for tracking. This thesis analyzes the many considerations required for designing and implementing a FSO PAT system, and extends this work to the rapidly expanding area of mmW DWN systems. Different types of beam acquisition methods are simulated and tested, and the tradeoffs between various design specifications are analyzed and simulated to give insight into how to best implement a transceiver platform. An experimental test-bed of six FSO platforms is also designed and constructed to test some of these concepts, along with the implementation of a three-node biconnected network. Finally, experiments have been conducted to assess the performance of fixed infrastructure routing hardware when operating with a physically reconfigurable RF network.