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.

Yes / A novel wideband printed monopole antenna is proposed covering frequency spectrum of wireless local area network (WLAN) and the Worldwide Interoperability for Microwave Access (WiMAX). The total antenna size is 30 × 48 × 1.6 mm³ in which it consists of a G-shaped slotted printed antenna and a defected ground plane. Theoretical and experimental characteristics are presented and compared. The antenna yields an achieved impedance bandwidth of 95.1% between 2.374 GHz and 6.682 GHz at a reflection coefficient |S11| ≤ -10 dB.The results including S-parameters, surface current distribution, VSWR, radiation patterns and antenna gains; in addition to a reasonable and stable radiation pattern and power gain.

Thesis (M.S. in Engineering Science)--Naval Postgraduate School, December 2003. / Thesis advisor(s): David C. Jenn, Roberto Cristi. Includes bibliographical references (p. 95). Also available online.

No description available.

No description available.

Thesis (M.S.)--Ohio University, March, 1993. / Title from PDF t.p.

Reconfigurable antennas represent a recent innovation in antenna design that changes from classical fixed-form, fixed-function antennas to modifiable structures that can be adapted to fit the requirements of a time varying system. Advances in microwave semiconductor processing technologies have enabled the use of compact, ultra-high quality RF and microwave switches in novel aspects of antenna design. This dissertation introduces the concept of reconfigurable antenna bandwidth control and how advances in switch technology have made these designs realizable. Specifically, it details the development of three new antennas capable of reconfigurable bandwidth control. The newly developed antennas include the reconfigurable ring patch, the reconfigurable planar inverted-F and the reconfigurable parasitic folded dipole. The relevant background work to these designs is described and then design details along with computer simulations and measured experimental results are given. / Ph. D.

No / It is shown that a conical beam 5.2-GHz antenna suitable for HIPERLAN application, but working in horizontal polarization, can be realized as a group of microstrip patch radiators in a ring formation. Layouts with three and four patches are described, and radiation patterns are found to agree well with predictions from a simple array model. The three-patch form is smaller and gives a closer approximation to an azimuth-independent pattern. Patterns are very similar to those achieved in vertical polarization with previously reported disk antenna realizations, giving peak radiation at about 50 elevation. Two methods of impedance matching are found to give satisfactory results. A dual-polarized conical-beam microstrip antenna, with a strictly uniplanar conductor pattern, is also presented and realized as an array of three square patches whose corners meet a central feed point. For the second polarization, the antenna functions as a series fed array. Fairly good conical beam patterns have been obtained, though only moderate polarization purity appears to be obtainable from threeelement arrays.

Yes / A frequency tuned antenna has been designed to meet the coverage requirements of the DCS, PCS, UMTS and WLAN bands. The antenna consists of a main patch, and a planar inverted L (PIL) slot. The radiator patch is fed, and shorted, using simple feed lines with broadband characteristics. The handset represents the finite ground plane, and a varactor diode is mounted across the middle of the slot for tuning purposes. Initial tuning was obtained by placing lumped capacitors, instead of the varactor, over the radiator. Good agreement is obtained between the predicted and measured input return loss, gain and radiation pattern over the tuned frequency range. / MSCRC