【作者】 余彦民；

【导师】 吴文； 吴锡东；

【作者基本信息】 南京理工大学 ， 电磁场与微波技术， 2011， 博士

【摘要】 分形曲线具有高效的空间填充性和自相似性,所以采用分形技术的天线可以充分填充有限的空间区域,从而增加天线的电长度,这种特性可以缩小天线尺寸,同时获得多频带或者宽频带特性。单极子天线由于结构简单,被广泛应用于各种通信系统,但是传统单极子天线过大的尺寸不仅影响移动搭载平台的气动性,特别是机载环境,还降低了天线的生存能力。本文围绕减小单极子天线高度,增大阻抗带宽,对顶部分形加载单极子天线进行了理论和实验研究,具体工作如下：1.结合分形曲线的放缩,从电流分布的角度阐明了顶部分形加载对于单极子天线高度的压缩原理。针对单纯顶部分形加载时天线输入电阻过小而难以匹配的问题,提出了在分形曲线两端加载短路柱的方法。实测结果表明：顶部Hilbert和Peano加载单极子天线在λ/14的高度下,分别实现了15.7%和13.7%的相对阻抗带宽。2.针对搭载空间有限的情况,分析了有限金属接地面对顶部分形加载单极子天线阻抗带宽和方向图的影响。分析表明：设计金属接地面的尺寸可以有效调节天线E面方向图的波束指向和3dB波束宽度。3.为了进一步提高顶部分形加载单极子天线的宽带工作能力,提出了多短路柱加载方案。实测结果表明,采用该方案后顶部一阶和二阶Peano分形加载单极子天线的相对阻抗带宽分别提高为25.8%和27%。4.为了进一步减小天线的高度和顶部填充空间,提出了对顶部分形加载单极子天线加载集总阻抗网络的方案。分析表明：在顶部填充尺寸增加时,顶部二阶Peano分形加载单极子天线的电高度可以再减小50%；在顶部填充尺寸不变时,天线的电高度可以再减小26.7%。更多还原

【Abstract】 Fractal antenna can achieve multiband or wideband characteristic with small size due to its efficient space-filling and self-similarity, which is very attractive for modern wireless communications such as mobile platform and airborne platform. In this dissertation, antenna miniaturization and bandwidth enhancement have been studied by introducing fractal loading on the top of monopole. The main contributions of this dissertation are listed as follow:Based on the current distribution of scaled fractal curve, the principle of reducing the height of fractal loaded monopole antenna is given. Shorting pins are introduced at the end of fractal structure for impedance matching. Measurement shows that Hilbert and Peano fractal loaded monopole antennas achieve 15.7% and 13.7% impedance bandwidth in the height ofλ/14, respectively.Next, effects of finite ground plane are investigated. Simulations show that it is an effective method to adjust E-plane beam bearing and 3dB beamwidth by adjusting the finite ground plane size.Next, multiple shorting pins technique is introduced to further enhance the impedance bandwidth of the proposed fractal loaded monopole antennas. Measurements show that a bandwidth improvement of 25.8% and 27% is achieved for the 1st order and 2nd order Peano fractal loaded monopole antennas, respectively.In addition, a lumped network is studied as loading for reducing the antenna height and loading area. There is a trade-off between the required antenna height and loading area according to simulations. For example, with the increase of loading area, the 2nd order Peano fractal loaded monopole antenna can achieve a 50% decrease on antenna height. When the loading area remains unchanged, the monopole antenna can achieve a 26.7% decrease on antenna height.更多还原