【作者】 丁敏；

【导师】 金荣洪；

【作者基本信息】 上海交通大学 ， 电磁场与微波技术， 2010， 博士

【摘要】 近年来,对通信系统的大容量、高可靠和高品质化的要求普遍迅速增大,多种多样的服务正在出现。针对无线应用的新技术和新标准也是层出不穷,在满足工作和生活需要的同时也极大的促进了无线技术和相关产业的发展。通信系统的飞速发展对通信设备提出了越来越高的要求。通信设备的体积不断减小,通信频带不断向宽频段、高频段发展,推动了作为通信系统中的关键部件天线的小型化和宽带化的发展。因此高性能小型宽带天线的研制己成为一个紧迫且具有重大理论和实际意义的课题。本文阐述了目前通信系统小型宽带天线的设计理论、限制及国内外研究现状,对小型宽带天线的研究内容如下:第一,设计多种新型超宽带(UWB)天线结构,包括小型分形超宽带天线和全向带阻超宽带天线。本文对分形的基本理论、构造方法以及分形在天线设计中的应用特点做简单的说明,引入了分形几何概念,利用分形技术的自相似性和空间填充性来实现小型超宽带天线的设计。实验结果验证了该天线工作带宽可完全覆盖UWB应用所需的3.1GHz到10.6GHz频段。另外,本文对带阻超宽带天线进行了研究。在带阻超宽带天线的设计中,给出一种倒梯形超宽带天线的设计过程,在此超宽带天线结构上开一倒梯形缝隙来实现频率从5GHz到6GHz范围内的阻带功能,为了改善方向图的全向性,将平面带阻天线拓展成立体结构,设计了具有全向性的带阻超宽带天线。第二,用进化算法对小型超宽带天线进行设计。为了节省人工调节天线参数的时间,本文采用遗传算法(GA)与时域有限差分方法(FDTD)相结合,在已知的基本结构上,通过遗传算法优化天线结构参数,同时提出了一种适合于优化超宽带天线和带阻超宽带天线的适应度函数,由时域有限差分方法计算适应度函数值,优化设计了一种频率范围从3GHz到11GHz的超宽带天线。为了在有限的尺寸上设计出高性能的超宽带天线,本文用二维遗传算法(2-D GA)对超宽带天线和带阻超宽带天线进行自动设计,并设计了两款小型超宽带贴片天线。为了克服遗传算法收敛速度慢的缺陷,本文还采用二维遗传算法和二进制粒子群算法(BPSO)相结合自动设计了一小型的超宽带天线,加工测试结果显示此超宽带天线在相对介电常数为2.65的介质板上24mm×24mm的面积内实现了几乎在3.1GHz-10.6GHz频带范围内小于1.5的驻波比特性。第三,本文利用金属反射板反射电磁波提高增益原理设计了两种天线阵列,包括用于无线局域网(WLAN)系统的小型可重构天线阵列,和用于卫星通信系统的宽带天线阵列。在用于WLAN系统的可重构天线阵列的设计中,天线不仅可以实现方向图全向/定向转换,而且还可用于多入多出(MIMO)系统中的方向图分集。在用于卫星通信系统的宽带天线组成的阵列设计中,比较了两种阵列单元组阵的结果,表明本论文设计的分形天线结构实现的阵列带宽及增益都要优于传统圆形贴片单元组成的阵列。更多还原

【Abstract】 Recently, the requirement of large capacity, high reliability and high quality in wireless communication systems is increasing generally and a variety of service is emerging. New technologies and new standards in wireless applications are coming out one after the other, and promoting the development of wireless technologies. The rapid development of communication system raises higher demand for communication equipments. Small volume and wide band of the communication equipment put forward the development of miniature and wideband antennas, which are known as key components of the communication systems. So the development of miniature and wideband antennas with good performance is an urgent and important issue in theory and applications. In the dissertation, the design principle, limitation and the status quo at home and abroad about miniature and wideband antennas are described. The thesis mainly consists of following parts:First, two new ultra-wide band (UWB) antennas are designed, including miniature fractal UWB antennas and band-notched UWB antennas. After the basic theory, the formation method and the characteristics of the fractal geometry are introduced, the self-similar characteristics and space filling property of the fractal geometry are used to design a miniature UWB antenna. Test results verify that the UWB antenna covers the frequency scale from 3.1GHz to 10.6GHz. In addition, a new UWB antenna structure with band-notch is also given, which is constructured by embedding an inverse trapeziform gap into the structure to realize 5GHz to 6GHz band-notched function. To improve the omnidirectional characteristic of the radiation pattern, the planar structure is extended to solid structure. The band-notched UWB antenna with omnidirectional radiation pattern is designed.Secondly, intelligent algorithm is used to design of UWB antennas. To save the time, the mixed model of genetic algorithm (GA) and finite-difference time-domain (FDTD) is used to optimize structure parameters of UWB antennas in the dissertation. The fitness function is evaluated by FDTD. A new UWB antenna from 3GHz to 11GHz is designed by this method. To design a UWB antenna in limited size, the 2-dimension genetic algorithm (2-D GA) is used to design automatically UWB antennas and band-notched UWB antennas. To avoid the slow convergence rate in GA, the 2-D GA and the binary particle swarm optimization (BPSO) is mixed. A UWB antenna with 24mm×24mm sizes and less than 1.5 VSWR from 3.1GHz to 10.6GHz is designed by the method.Finally, a metal reflector is adopted for adding the gain of antenna arrays, including the miniature reconfigurable array for wireless local area networks (WLAN) systems and wideband array for satellite communication systems. In the design of miniature reconfigurable array, not only the omni-directional/directional radiation switch is realized, but also pattern diversity in the multi-in multi-out (MIMO) systems is realized. In the design of the array for satellite communications, the array structure not only increases the bandwidth, but also improves the gain of the array. The characteristics of the arrays constituted by the fractal structure and the traditional disc structure are compared. The results prove the superiority of the fractal structure.更多还原