Critical Analysis Of Transmitarray Antenna Design

In recent years, transmitarray antenna concept attracts growing interests of many scientists in the antenna area. It combines the favorable features of the lens antenna that are based on optical theory and the microstrip arrays that are based on array theory, leading to a low profile design with high gain, high radiation efficiency, and flexible radiation performance. Transmitarrays are now emerging as a new generation of high-gain antennas for long-distance communications. In this dissertation, comprehensive analysis, new methodologies, and novel designs of transmitarray antennas are presented. * detailed analysis of the design of planar space fed array antennas is presented. The basics of the aperture phase distribution and the analysis of the array elements are described. The radiation performances of the space fed arrays are discussed using the array theory approach. Three approaches for directivity and gain calculations are presented. Causes and contributions of element phase errors are demonstrated. * the transmission performance of transmitarray design using multilayer frequency selective surfaces (m-fss) approach is carefully studied, and the transmission phase limit of m-fss structure is revealed. The maximum transmission phase range is determined based on the number of layers, substrate permittivity, and layer separations. These analytical limits are generally applicable independently from the selection of a specific element shape. * a high gain quad-layer transmitarray antenna using cross-slot elements with no dielectric substrate has been designed, fabricated and tested at x-band. This design has the advantages of low cost and suitability for space applications. Furthermore, a detailed analysis considering the oblique incidence angles and the feed polarization conditions is performed, aiming to study their impacts on the antenna gain and the radiation patterns. * in order to reduce the transmitarray design complexity and cost, three different methods to reduce the number of transmitarray layers have been investigated. Based on this analysis, a novel high gain broadband triple-layer transmitarray antenna using spiral dipole elements has been designed, fabricated and tested at x-band. * new design methodologies are proposed to improve the bandwidth of transmitarray antennas through the control of the transmission phase range and by optimizing the phase distribution of the transmitarray elements. These design techniques are validated through the fabrication and testing of two quad-layer transmitarray antennas at ku-band. * the feasibility of designing single-feed transmitarray antennas with simultaneous multiple beams is investigated. Phase synthesis is achieved using the particle swarm optimization method. A ku-band single-feed quad-beam transmitarray antenna with 50 degree elevation separation between the beams are designed, fabricated and tested. In summary, different challenges in the analysis and design of transmitarray antennas are addressed in this dissertation. Critical analysis of unit-cell element design of multilayer transmitarray antennas has been studied. New methodologies to improve the bandwidth of transmitarray antennas have been demonstrated. Several prototypes have been fabricated and tested, demonstrating the desirable features and potential applications of transmitarray antennas. These novel designs include a transmitarray antenna with no dielectric substrate, a high gain and broadband transmitarray antenna with only three conductor layers, two wideband transmitarray antennas, and a single-feed quad-beam transmitarray antenna