الفهرس 
CHAPTER 1: IntroductionOnly 14 pages are availabe for public view
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Abstract
In recent years there has been a growing demand for reduced weight, small launch volume, and, at the same time, high-gain large-aperture antenna systems in modern space-borne applications and satellite communications. This thesis addresses the design and analysis of different reflectarrays and transmitarray antennas to meet these requirements. A reflectarray is made up of an array of radiating elements that provide a preadjusted 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. The reflectarray antennas design in this work includes five antennas. The first antenna is designing sector reflectarrays on conformal cylindrical and spherical surfaces for many practical applications where a curved platform is available, such as missiles and aircrafts. The radiation characteristics of reflectarray are investigated and compared with that of planar reflectarray. The effect of curvature angle on the reflectarray antenna performance is explained. The reflectarray antenna embedded in a cylindrical and spherical surfaces to protect the array are investigated. The embedded structure for all cases gets more directivity and more practical protection due to the coated materials. Full-wave analysis using the finite integration technique (FIT) is applied. The results are validated by comparing it with that determined by transmission line method (TLM). The second reflectarray is a tunable reflectarray based on elements tuned using varactor diodes for beam steering. The reflectarray element consists of a C-shaped patch, printed on a substrate loaded with one varactor diode. It is known that varactor diodes can be used as phase shifting devices by varying the reverse voltage applied to it to change its capacitance. This can be utilized to achieve the realization of scanning antennas. The reflectarray is designed to operate at 13 GHz. It is composed of 21x21 elements with area 27.3 x 27.3 cm2. The reflectarray is fed by linearly polarized pyramidal horn antenna. The mutual coupling between the feeding horn and the
elements of the reflectarray is considered. The normalized gain patterns, the frequency bandwidth, and the aperture efficiency for the reflectarray are determined. The third reflectarray is a wideband perforated rectangular dielectric resonator antenna (RDRA) reflectarray. The arrays of RDRA are formed from one piece of dielectric material. Air-filled holes are drilled into the material around the RDRA. This technique of fabricating the RDRA reflectarray using perforations eliminates the need to position and bond individual elements in the reflectarray and makes the fabrication of the RDRA reflectarray feasible. The ground plane below the reflectarray elements is folded as a rectangular concave surface so that an air-gap is formed between the RDRA elements and the ground plane in order to increase the bandwidth. Three cases are studied. In the first one, the horn antenna is placed at the focal point to illuminate the reflectarray and the main beam is in the broadside direction. In the second one, the horn antenna is placed at the focal point and the main beam at ±30 degrees off broadside direction. In the third one, an offset feed RDRA reflectarray is considered. The radiation properties of these reflectarray antennas have been investigated. The fourth reflectarray is the plasma reflectarray. The proposed unit cell consists of cubic glass box filled with Argon gas energized with applied DC voltage. The reflectarray reflection coefficients phase variation is achieved by varying the plasma frequency of the energized gas. Four plasma reflectarrays for satellite applications at 12 GHz are proposed (centre-feed centre-beam, centre-feed offset-beam, offset-feed centre-beam, and finally offset-feed offset-beam). The last reflectarray is perforated nanoantenna reflectarray for applications such as spectroscopy, photovoltaic and optical imaging. Reflectarray consists of an array of unit cells made of Silver is investigated to operate at 735 THz. A comparison between solid Silver sheet with no perforation holes and the proposed perforated reflectarray is presented.
The second part in this thesis discus five designs of the transmitarray. The first transmitarray is single layer transmitarray antenna using rectangular
dielectric resonator as the unit cell elements. Two different constructions for the unit cell of the transmitarray are used. The first one consists of two RDRA elements on either side of a substrate material. In the second transmitarray, the two RDRA elements on either side of a perfect conductor ground plane are placed and coupled by a rectangular slot. RDRA elements of varying lengths are used to shape the phase of the wave front of incoming wave and maximize the transmission through the structure. Using these transmitarray cell elements, a 21x21 transmitarray was designed. The transmitarray is designed for operation at X-band and design frequency is chosen as 11.2 GHz. A transmitting linearly polarized pyramidal horn antenna is used to illuminate one side of the transmitarray. The second transmitarray is circularly polarized transmitarray at 10GHz for satellite application by using square DRA element fed with circularly polarized horn antenna. The third transmitarray is a dual-polarization dual-band transmitarray for satellite applications. This transmitarray is designed for two frequency bands: 17.15 GHz to 17.9 GHz for vertical polarization and 11.5 GHz to 12.4 GHz for horizontal polarization. The dual polarization is obtained by an independent adjustment of the dimensions of two orthogonal slots in the transmitarray unit cell. The design is carried out independently for each polarization. The transmitarray unit cell uses two dielectric substrate layers arranged to be one on each side of a conducting plane. On each substrate, one face has metallization containing the patches, and the other face has metallization containing the ground plane. The two patches are coupled by two cross slots of lengths LV and LH in the ground plane and each patch is loaded with two cross slots of lengths LV/2 and LH/2. A circular feed horn is located on the central normal to the transmitarray and the configuration looks like a lens antenna. Two separate feeding pins are used to excite the horn antenna for horizontal and vertical polarizations. The fourth transmitarray is perforated transmitarray for wideband application. The transmitarray is formed from a single dielectric sheet by perforating selected areas of the material. A perforated dielectric layer is divided into square cell elements. Each cell has
four holes with the same diameters. Holes with different diameters in the cell elements are used to allow continuous tuning of the transmitted signal’s phase. The focal-to-diameter ratio of the transmitarray is optimized for lower side lobe level and highest transmitarray gain. A comparison between the transmitarray and the reflectarray with the same aperture area is illustrated. The radiation characteristics of the concave and convex transmitarrays with different focal length to diameter ratio and different subtended angles are investigated and compared with that of the planar transmitarray. The last transmitarray is a multilayer dielectric resonator antenna transmitarray for fixed RFID reader applications is presented at 5.8 GHz. Three layered square DRA element mounted on dielectric substrate is used as a unit cell in the transmitarray. The dimensions of the unit cell and the number of layers are optimized to give phase distribution of the transmission coefficient from 0 to 2π. A circularly polarized 9×9 square DRA transmitarray is designed at 5.8 GHz for far-field RFID applications. A design of 9×9 near-field focused DRA transmitarray for fixed RFID at 5.8 GHz is investigated. The properties of the NF-focused transmitarray are compared with the far field transmitarray designed at the same operating frequency.