| The rapid development in the fields of ultra wide band (UWB) radar, UWB communications, UWB imaging and UWB electromagnetic pulse weapon and so on becomes a tremendous impetus for studying UWB antenna while ever-increasing requirements are proposed for UWB antenna design. Among various forms of UWB antennas, transverse electromagnetic (TEM) horn antenna and its transformative forms are commonly used in domain of high power microwave, working under TEM mode.They have strong-directional radiation and are easy to project implementing.They also have constant impedance characteristics in very broad frequency range and radiate time-domain narrow pulse signal effectively. Because of the limitation factors of feed, size, power, etc. and consideration of antenna-radiation controllability, it is fit for applying array technology to reduce the beam width and side lobe level and improve the radiation power. They have wide application prospects in the realm of military and civil, such as radar system, electronic warfare, underground detection and the like.There are not only some difficulties in UWB antenna analyzing, but also more challenges in UWB antenna synthesis and optimization. Because of the strong nonlinearity between the optimized variables and optimized objects of UWB antenna array, the traditional optimization methods sometimes can not deal with it. In spite of this, studying on more suitable and high-powered optimization methods for UWB antenna array is very necessary and urgent, which may influences the performance and optimization speed of antenna array directly.In this dissertation, finite-difference time-domain method (FDTD) is applied to be the basic analysis method for electromagnetic radiation problems and micro genetic algorithm (MGA), improved micro genetic algorithm (I-MGA) and improved multi-objective evolutiaonary micro-genetic algorithms are used to process the optimization problems of antenna and array respectively.Firstly, FDTD is introduced here as UWB antennas analysis method, whose advantages and the involved algorithms will be discussed. A simple FDTD model for transient excitation by transmission lines is expound, which divides the computational region into excitation source region and antenna region to reduce computational cost. The improved rapid time-domain near-far extrapolation method based on FDTD calculations is used to obtain far-field information of antennas. In order to minimize the calculation data for far-field transforming, the data in Huygens' equivalent surface are sampled in space-domain or time-domain, which saves the computing time consumedly. An example is given.Secondly, the definition of parameters that describe the time-domain characteristics of UWB antenna and the method for antenna modeling are introduced. The validity of program is proved subsequently. After that the radiation characteristics of TEM horn antenna are told out. The impact of antenna variables' changing on its radiation characteristic is analyzed. Then the superposition principle of UWB antenna array, the different influence of array arrangement style, mutual coupling effect between array elements and time-domain electric scanning characteristic are introduced. The transformative antennas of TEM horn antenna, dielectric loaded TEM antenna and double-ridged TEM horn antenna, are also simulated, whose characteristics are analyzed as well.Thirdly, the involved optimization algorithms focusing on the realization of UWB TEM horn antenna design are mainly discussed here. The different process measures for sigle-objective and multi-objective optimization problem will be mentioned.The advantage and disadvantage of traditional optimization algorithms and the characteristics of stochastic optimization algorithms are introduced subsequently.The criterion of performance evaluation of the stochastic optimization algorithms will be given as well. Micro genetic algorithm (MGA) is compared with genetic algorithm (GA). The former who searches more efficiently is improved here and the improved micro genetic algorithm (I-MGA) is proposed, whose performance is tested. In addition, two different forms of improved multi-objective MGA are designed based on non-domain Pareto optimal concept for multi-objective optimization problem.The two kinds of multi-objective optimization algirithms are tested by testing functions, compared with the other optimization algorithm. The detail is presented.In addition, MGA, I-MGA and improved multi-objective evolutiaonary micro-genetic algorithms are combined with FDTD respectively for UWB antenna array optimization problem. We take gain, beam-width, side lobe level, etc. as the optimization objects, changeing the high-order equation groups that are hard to solve to be the restrict conditions of evaluation fitness. MGA and I-MGA are applied to optimize the electric and geometric design variables and so on while radiation problem is analyzing by FDTD. This dissertation discusses the single antenna optimization and array optimization problems here. For multi-objective optimization problem, we use weighted sum approach and Pareto-based approach respectively to proceed. In order to further accelerate the optimization speed, combination-optimization method is proposed. Regardless of couple effects of array elements, we optimize the antenna array for the first time to acquire prior knowledge. After that, according to the first optimization results, we take the couple effects into account and do secondary optimization to get the final outcome.Finally, the work is summarized and the next research directions are predicted.In this dissertation, we start from full-time domain optimization algorithm and improve the performent of the optimization method of UWB antenna array. Combined with FDTD, the optimization of UWB TEM antenna array is achieved.
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