Pattern Reconfigurable And Conformal Microstrip Antenna Array

Reconfigurable antenna, which contains the function of several antennas, has many advantages, such as small dimensions, light weight and meeting the needs of different environments. Therefore, it has become a research hotspot recently. Reconfigurable antennas can be divided into the following categories according to their performance, i.e., frequency reconfigurable antennas, pattern reconfigurable antennas, frequency and pattern reconfigurable antennas and polarization reconfigurable antennas. There are extensive applications for reconfigurable antennas. For example, the pattern reconfigurable antenna, whose radiation pattern can be adjusted, can be used in many situations to meet different requirements. Wider scanning angle can be achieved if adopting pattern reconfigurable antennas as the elements of phased array. With regard to the conformal array, besides the scanning range being expanded, the convergence ability of the gain will be improved as well, when the pattern reconfigurable antennas acted as the array elements. Researches on pattern reconfigurable antenna elements and reconfigurable planar arrays are performed, and reconfigurable conformal arrays are also investigated. The thesis includes the following six chapters.The first chapter introduces the background and the state of the art of reconfigurable antennas at home and abroad. The structures, functions and reconfiguration methods of the reconfigurable antennas are given in detail as well. Knowledge about the pattern reconfigurable planar array and pattern reconfigurable conformal array are introduced briefly.Chapter II introduces the theories of microstrip antenna and Yagi-Uda antenna. Besides, knowledge of the array, including the conformal array, and the preliminary application of the active element pattern technique are provided.Chapter III presents the design of a pattern reconfigurable triangular patch Yagi antenna. Firstly, according to the principles of Yagi-Uda antenna and microstrip antenna, the pattern reconfigurability mechanism of the proposed antenna is explained in detail. Next, the antenna performance using different switches is investigated by simulation, such as ideal switches, PIN switches and RF MEMS switches. Finally, based on the proposed antenna, a planar pattern reconfigurable antenna is designed, which has scanning angle coverage over the azimuth range of360°in the upper space.In Chapter Ⅳ, a reconfigurable microstrip array is introduced, of which the pattern reconfigurable Yagi-Uda patch antenna used as the array element. By decreasing the number of parasitic patches, the dimensions of array elements as well as the elements space are decreased, which results in the reduction of side lobe level. In order to achieve better beam scanning ability, the elements at different locations contain different numbers of patches, which may be at different states (dynamic elements). This reconfigurable patch array has advantages over a conventional microstrip patch array, such as wider scanning angle, lower side lobe level and flatter gain fluctuation.Chapter Ⅴ studies the characteristics of the cylindrical conformal arrays comprised of reconfigurable antenna elements. The beam convergence ability of the conformal array is investigated by simulation, in respect of the cylinder parameters and the element structures.The last chapter gives the summary of the whole thesis.