الفهرس | Only 14 pages are availabe for public view |
Abstract With the advent of the information era, numerous advanced communication technologies have arisen during the past two decades, which, have greatly influenced and benefited every field of human society. With the need for increasing the data rate of wireless systems, the ultra wideband (UWB) technology seems to be an ideal candidate for future radio communication systems in various types of networks. UWB technology has been swiftly evolving as one of the most promising wireless technologies that provide the high bandwidth required by the latest and future portable home and office devices for multiple digital video and audio streams. UWB technology has been applied in many areas such as radar, remote sensing and military and entertainment communications. Microstrip patch antennas (MPAs) are widely used in the microwave frequency region because of their simplicity and compatibility with printed-circuit technology and ICs, making them easy to manufacture either as stand-alone elements or arrays. In this thesis, probe fed rectangular microstrip patch antennas are investigated to meet UWB requirements. The effect of patch dimensions, patch shape, dielectric material, dielectric height, probe radius, and probe position on the operating impedance bandwidth is investigated. Time domain characteristics are also investigated to meet the required characteristics. New eight UWB probe fed rectangular MPAs are introduced and all meet the required UWB characteristics. A combination of multiple techniques is used to widen the operating impedance bandwidth. Substrate superstrate technique is also used to improve the operating impedance bandwidth. The peak gain and radiation efficiency are simultaneously improved. Also the antenna group delay is greatly improved. FEM via HFSS is used to simulate the proposed antenna structures. Also a MATLAB program based on FDTD method is prepared and tested to verify the characteristics of the proposed UWB MPAs. FIT via CST MWS is sometimes used to verify the introduced structures when FDTD needs large computational time and memory. |