الفهرس 
CHAPTER 1: INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The Thesis addresses the design of different types of dielectric resonator (DR) reflectarray antennas used in satellite and radar communications. The concept of the reflectarray antenna was introduced in 1963 using waveguide elements, but the real interest in reflectarrays only came about in the late 1980s with the development of low profile printed antennas. For this reason, the printed reflectarray can be considered as a fairly new type of antennas. A reflectarray is made up of an array of radiating elements that provides a pre-adjusted phasing to form a focused beam when it is illuminated by a feed, in a similar way to a parabolic antenna. Printed reflectarrays combine certain advantages of reflector antennas and phased arrays. They are manufactured on a planar substrate using printed circuit technology and offer the possibility of beam steering as phased arrays. On the other hand, the feeding mechanism (as in a reflector antenna) eliminates the complexity and losses of the feeding network used in planar arrays, thus providing a higher efficiency. Reflectarrays have demonstrated their capability to produce beamforming, which are conventionally generated by using shaped reflectors or phased arrays. However, there is one major shortcoming of the reflectarray, which is its narrow bandwidth behavior, but the bandwidth has been significantly increased in recent developments. The purpose here is to present typical types of DR-reflectarray antennas, including the operating principles, their advantages over other antennas, their development history, analysis, practical design procedures, bandwidth issues, and wideband techniques, as well as their applications and recent developments. Linearly polarized models of DR-reflectarray at X-band with more details about the design steps that must be taken into account during the design of a reflectarray antenna, such as the selection criteria for the phasing elements and the appropriate 1 spacing to provide enough phase range and avoid the appearance of grating lobes are explained. These aspects are essential to achieve a good efficiency. The phase figure calculation and antenna performance are discussed with good agreements between finite integral technique (FIT) and transmission line method (TLM). The bandwidth in reflectarrays is mainly limited due to the phase response of the radiating element. Several reflectarray models are presented to improve the bandwidth by using DRA elements. Aperture-coupled DR-reflectarray is the best reflectarray, which achieves more than 53% radiation efficiency comparing with patch reflectarray which reaches 35%. More broadened bandwidth is satisfied by new DRA cell, which uses two identical DRAs rather than a single DRA per cell. A single-feed dual-beam covering two areas is designed. A dual-polarized DRAreflectarray is also investigated. Circularly polarized models of DR-reflectarray at X-band with more details about the ideas of getting circularly polarized reflected wave using linearly polarized feed and circularly polarized feed are illustrated. The phase figure calculation and antenna performance are discussed with good agreements between FIT and TLM. A crossed DRA element, DRA supported on ground plane with crossed slot and aperture-coupled DRA supported on crossed slot with crossed strip lines are investigated with good axial ratio and accepted gain. Finally, active beam scanning reflectarrays are presented in some details. Active electronic components for beam scanning with wide scanning angles have been implanted within aperture-coupled DR-reflectarray antenna.