在现代通信技术中，为了实现通信保密、排除干扰、提高通信效率等，超宽带系统得到了大力发展，然而，在一定程度上却受制于系统中超宽带天线的阻抗带宽。详细介绍了展宽天线阻抗带宽的4种方法，包括渐变阻抗方法、分形几何方法、微带天线开槽方法和非频变结构方法，其中分形几何方法由于其几何结构的自相似性使得其贴片电流分布具有自相似性，从而导致天线的多频点谐振，有效拓展了天线带宽。上述4种天线尽管作用原理互不相同，但在超宽带天线的工程应用中，研究者可将这些方法单独或同时应用于天线结构设计，使得天线既能保持良好的方向性和增益等性能，又能获得较大带宽。%In modern communication technology,multi-band technology and ultra-wideband ( UWB) sys-tems are widely employed in order to achieve confidential communication,eliminate interference as well as improve communication efficiency. However,the impedance bandwidth of antennas in these systems hinders the development of UWB systems to some extent. In this technology background,this paper investigates four techniques which can broaden the impedance bandwidth of antennas. These methods include gradient struc-ture,fractal structure,slotted structure on micro-strip antennas as well as frequency independent technolo-gy. Among them,the fractal structure due to the self-similarity of its geometry makes its current distribution has self-similarity on the patch, resulting in several multi-frequency resonance points in the antenna, which will effectively broaden the bandwidth of the antenna. Although the theoretical principles of broade-ning bandwidth of the four methods are different,researchers can apply these techniques separately or sim-ultaneously in UWB antennas in engineering applications. The application of these methods guaranties mi-crowave antennas to possess maximum bandwidth,optimum gain and meanwhile good radiation pattern.
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