Millimeter-wave Electromagnetic Band-gap Structures for Antenna and Antenna Arrays Applications.

摘要

Recently, communication systems and applications have been driven toward the millimeter-wave band (MMW). In addition to the emerging demands of compact, high-speed, and large bandwidth systems, the crowd of RF bands, and the commercial availability of MMW components have made the MMW band a suitable choice for many short-range wireless applications. Moreover, compared to the ultra-wide band (UWB), MMW bands are free of major interference sources that UWB systems may suffer from. udHowever, and from antenna designers’ point of view, MMW bands suffer from the high attenuation characteristics associated with these bands. Therefore, researchers have proposed several techniques to overcome this problem. Nevertheless, most of these techniques have proven major drawbacks that negatively affect the antenna performance. udFurthermore, and due to the compact sizes of the circuits and components at the MMW bands, the mutual coupling between antenna array elements has becomes a big concern that deteriorates the efficiency of the communications systems, especially in multiple-input-multiple output (MIMO) systems, where it has been proven that mutual coupling strongly affects the systems capacity. udTherefore, the main research in this thesis work consists of several investigations and techniques on increasing the gain and improving the radiation characteristics of complex-structured MMW antennas by using Electromagnetic Band-Gap (EBG) structures. Experimental results show the advantages of these techniques over those exist in the literature. udMoreover, the applications of Mutual-coupling reduction in Antenna arrays at MMW wave bands new compact EBG unit-cell is introduce in this work. It has been proven to effectively reduce the mutual coupling between antenna array elements at MMW bands. udReconfigurable radiation pattern antennas are in the scope of this work. Their ability to meet the demands of emerging communication systems and applications by producing diversity in radiation pattern, polarization, and frequency made them very attractive to be used in the MMW bands.