Thesis (Ph. D.)--University of Idaho, 2006. / Abstract. "April, 2006." Includes bibliographical references (leaves 279-288). Also available online in PDF format.

Report (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Abstract. Includes bibliographical references (leaf 26). Also available via the Internet.

No description available.

This thesis addresses the use of an electronic reconfigurable surface (ERS) attached to an axisymmetric paraboloidal reflector antenna to mitigate interference through nulling for radio astronomy applications. The ERS is a reflectarray that consists of multiple elements, which can be electronically controlled to modify the reflected field. Previous research focused on a "conformal" system with elements placed on a parabololoidal surface extending beyond the unmodified reflector. These studies concluded that nulling could be achieved without compromising the gain and shape of the main lobe. This thesis builds on previous research by addressing two topics. The first topic is minimization of the ERS rim width. A closed form expression for the minimum width required for effective nulling in the close-in sidelobes is derived in this thesis. The second topic addressed in this thesis is ERS configurations comprised of flat panels as an alternative to the conformal ERS implementation. Flat panels may be easier to manufacture compared to their conformal counterpart. Flat panel ERS implementations are evaluated, and it is concluded that they are a suitable alternative to conformal ERS implementation. / Master of Science / This thesis utilizes the state-of-the art electronic reconfigurable surface (ERS) attached to a reflector antenna to mitigate interference for radio astronomy applications. The ERS is an array that can be controlled electronically to modify the radiation from the reflector. Previous research focused on configuring the ERS attached conformally to the reflector to null interference in a direction. This thesis appends previous research by addressing two topics. The first topic is the minimization of the ERS width for the conformal implementation. A closed form expression for the minimum ERS width is derived in this thesis. The second topic is to explore an ERS topology that consists of flat panels attached to the reflector. This topology is explored since flat ERS panels may be easier to manufacture. It is concluded that the flat panel ERS implementation is a suitable alternative to the conformal ERS implementation for interference mitigation.

No description available.

No description available.

published_or_final_version / abstract / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Wireless communication systems are limited in performance and capacity by the major impairments of multipath fading and co-channel interference. Smart antenna can combat the impairments, thereby enhancing the system capacity and alleviating the problem of bandwidth limitation. In general, there are two main types of smart antennas; these are switched beam systems and adaptive array systems. An antenna array, which consists of a group of several antenna elements and digital signal processing units, can form several independent beams in different angles. Smart antennas aim the main beam in the direction of the target mobile user and locate the nulls in the direction of the interfering signals from other mobile users to enhance the signal-to-interference power ratio and system capacity. One of the most important parts in adaptive array antenna systems is the adaptive algorithm to adjust the weights of an array. These algorithms include unconstrained as well as constrained LMS, normalized LMS, structured gradient, RLS, CMA, and conjugate gradient method. In this thesis, we propose a new algorithm based on weight-partition RLS method to reduce the computational complexity. The major concept of our algorithm is decreasing the dimension size of data matrix. Performance and complexity of the proposed algorithm is evaluated and compared with traditional WRLS algorithm.

Thesis (M.App.Sc.) - Carleton University, 2006. / Includes bibliographical references (p. 108-112). Also available in electronic format on the Internet.