【作者】 张鹏宇；

【导师】 邱景辉；

【作者基本信息】 哈尔滨工业大学 ， 电磁场与微波技术， 2011， 硕士

【摘要】 随着超宽带技术的飞速发展,超宽带天线的研究受到人们越来越多的关注。在点对多点的超宽带通信系统中,水平方向上信号的全向覆盖被要求,进而要求辐射或接收天线拥有超宽频带内稳定的水平方向全向辐射方向图。常用的超宽带全向天线包括拥有渐变结构辐射器的单极子天线等。本文以超宽带圆片单极子天线为基础,在保持超宽带特性的同时,努力改善其H面方向图的全向辐射特性。通过理论分析、计算机仿真和实物加工测试等手段,对天线的设计进行了系统的分析。通过对圆片单极子天线的仿真分析可知,该天线具有超宽的阻抗带宽,随着频率的升高H面辐射方向图由全向变为双向,对圆片的切削和翻折是两种有效的小型化手段。水平方向上几何结构的对称性是全向辐射的必要条件,因而提出了多圆片等角交叉的天线结构,并分析了圆片数目对各方向增益的最大差异的影响。仿真数据表明,随着圆片数目的增多,天线H面方向图的全向性变优,当片数不小于4时即可满足全向辐射条件；但随着圆片数目的增多,输入阻抗的实部逐渐变小、虚部逐渐变大,天线无法在超宽频带内实现阻抗匹配。通过仿真分析提出了一种双圆片嵌套结构,用以消除多圆片交叉结构对天线输入阻抗的影响,效果良好。用一个空心圆锥体代替单极子天线中的大尺寸地板,以实现天线水平方向上的尺寸小型化。根据以上分析,提出了超宽带半圆片交叉结构全向天线模型,并对其进行频域和时域的仿真分析,结果表明该天线具有极好的超宽带特性和全向辐射特性,时域特性亦能满足超宽带要求。以该天线模型为基础,加工了三个不同尺寸的天线实物并进行测量,测量结果与仿真结果基本一致,且证明了该天线极佳的超宽带潜能,可实现接近100:1的阻抗带宽。针对改进的超宽带半圆片天线,提出了若干种频带扩展和天线小型化的方法,具体包括多圆片嵌套结构、拉杆结构、电阻加载和顶部加金属圆片,仿真结果表明均为有效的改善天线阻抗特性的方法,有较高的实用价值。本文设计的天线在超宽带通信、电磁侦察等领域会有广泛的应用。更多还原

【Abstract】 With the development of ultra-wideband technology, research on UWB antennas gains more and more attention. In point-to-multipoint UWB communication systems, omni-directional coverage of horizontal signals is required, so the horizontal radiation pattern of the radiating or receiving antenna should be stable and omni-directional in the ultrawide frequency range. Common UWB omni-directional antennas are monopole antennas which have radiators of gradually variational structure.Design in this dissertation is based on UWB circular disk monopole antenna. Omni-directional radiation characteristic of H-plane radiation patterns should be improved as well as the maintenance of ultrawide bandwidth. Combination of theoretical analysis, computer simulation and prototype manufacture helps realize the systemic analysis of antenna design.Simulation of circular disk monopole antenna shows it has ultrawide impedance bandwidth, H-plane radiation patterns change from omni-direction to bi-direction with the increase of frequency, and cutting and turnover are two efficient miniaturization methods. The geometrical symmetric structure is the essential condition of omni-directional radiation, so antenna with multi disks crossed is proposed, and the effect of disk number on the maximal difference between gain in different direction is analyzed. The simulated results show that with the increase of disk number, the omni-directional characteristic of H-plane radiation pattern is improved, and the condition of omni-directional radiation can be met when the disk number is no less than 4. However, with the increase of disk number, the real part of input impedance gets smaller and the imaginary part gets larger which means the antenna can’t maintain impedance matching in the ultrawide bandwidth.An antenna with combination of two circular disks is proposed to eliminate the effect of multi-disk structure on the input impedance with good results shown. A hollow cone is used to replace the large ground plane in the monopole antenna in order to realize miniaturization in the horizontal plane. According to the analysis above, the UWB omni-directional antenna with crossed disks is presented and simulated in the frequency domain and the time domain. The results show that the antenna has excellent UWB characteristic and omni-directional radiation characteristic, and the time-domain characteristic also meets the UWB requirement. Based on this structure, three antenna prototypes of different dimensions are manufactured and measured with results consistent with simulated ones. Excellent UWB potential of this antenna is also certified which can realize a bandwith of approximately 100:1.According to the improved UWB semicircular disk antenna, methods of broadening the frequency range and miniaturization are proposed, including nested structure of multi disks, antenna with pulling poles, resistence loading and addition of top metal circular disk. The simulated results show that these methods all can improve the impedance characteristic of the antenna to a certain extent, showing great practical value. The antennas presented in this paper can be used widely in UWB communication, electromagnetic investigation and so on.更多还原