الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Nowadays, detection, locating, and imaging systems become indispensable nowadays due to the need for an efficient inspecting tool to be used in a variety of applications such as: nondestructive testing and evaluation (NDT &E), structural health monitoring, medical imaging, detection of cancerous cells, concealed weapon detection at security check points, and through-the-wall imaging. There are different imaging technologies used for see through purposes including: magnetic detection, ultrasound imaging, thermal infrared imaging, X-ray imaging, millimeter wave, and UWB radar imaging. Each technique has its own strength and weakness.
Ultra Wideband (UWB) signals are preferred for radar detection and imaging applications and more information about the targets can be obtained due to the short pulse duration and the broader bandwidth. UWB radar attracted the attention of many researchers nowadays. The commercial products for the through wall imaging solutions utilize UWB imaging technology. UWB radars are chosen in this thesis due to its fine resolution, good penetration into different materials, safe for consumers, and has the ability to work under all weather conditions.
This thesis aims to design a high gain UWB Vivaldi antenna array with the radiation flares in the form of elliptical curves. The antenna element has a triangular shape extension and a negative index metamaterial (NIM) perpendicular to the substrate. A detailed analysis is presented to prove that the NIM structure enhances the antenna gain by evaluating the effective medium parameters from the scattering parameters by applying the retrieval techniques. Then, a linear array is presented which consists of four identical antenna elements and the excitation coefficients are calculated according to the Dolph-Tschebyschev distribution. Due to the narrow half power beamwidth (HPBW) achieved by such array arrangement, the cross range resolution can be greatly enhanced. Also, the fabrication and measurement of the antenna array have been demonstrated.
In order to feed that antenna array elements, power dividers with UWB characteristics are required. An equal UWB power divider based on double open stubs is presented. The even and odd mode analyses have been presented to investigate the performance of the proposed UWB power divider which is based on double stub matching. In addition, an unequal UWB power divider is introduced which is based on the idea of multi-stage impedance ratio. There is a good agreement between simulated and measured results. Simple structure and compact size characteristics of the proposed dividers make them very useful in UWB applications and antenna array feed networks.
Finally, the antenna array element is assembled by connecting the four aforementioned UWB Vivaldi antennas with the unequal UWB power divider. The proposed array is simulated using CST for obtaining s-parameters and its radiation pattern. Two antenna arrays are used for buried metal target detection. The simulated results ensures the ability of the proposed system to detect metal buried objects.