论文总字数：25334字

摘 要

单极子天线具有结构简单，尺寸小，重量轻，成本低，全向性好的优点，已经广泛应用于各种通信系统中。但是它也存在很多缺点，例如由于单极子天线阻抗低，在匹配过程中带域变窄，很难达到宽带匹配；而且传统四分之一波长单极子天线在低频情况下剖面过高。为了适应更多的应用环境，往往需要它满足小型化和宽带宽的要求。本文研究分析了圆盘加载的单极天线的特性和规律，并在此基础上使用单层色散各向异性阻抗表面（Anisotropic Impedance Surface）在保持辐射特性的同时，增加其阻抗带宽，使传统的四分之一波长单极天线在高度降低的基础上带宽获得大幅增加。

首先通过在单极子天线上方加载金属圆盘的方式，将其在中心频率3GHz处的剖面高度从25mm（0.25λ₀）降低到15mm（0.15λ₀），此时圆盘尺寸为9mm，包围天线的最小球体半径由25mm降为15.66mm，实现了天线的小型化。然后在此基础上增加了柱形各向异性阻抗表面结构，通过等效理论电路模型得到各向异性阻抗表面理想的阻抗色散曲线，来控制天线在不同频率的响应。根据理想的阻抗色散特性设计出了可实现的各向异性阻抗表面结构，在不影响其辐射特性的基础上，使小型化圆盘加载的单极天线的带宽得到扩展。设计的宽带小型化天线的VSWRlt;2的带宽为2.64 - 5.02 GHz，比率带宽为1.90：1。在工作带宽内，天线增益为4.70 - 6.46 dBi，且具有稳定的垂直极化全向辐射方向图。

关键词：圆盘加载单极天线，各向异性阻抗表面（AIS），小型化，宽带天线

Abstract

The monopole antennas have the advantages of possessing a simple structure, a small size, light weight, low cost and good omnidirectionality, thus have been widely used in various communication systems. However, they have certain inherent shortcomings, such as it is difficult to achieve broadband matching because of the low impedance of monopole antennas; and traditional quarter-wave monopole antennas have a high profile. In order to adapt to more versatile application scenarios, they are often required to be miniaturized and have a wide operational bandwidth. In this thesis, the characteristics of the top-hat monopole antenna are analyzed. In addition, a single-layer dispersive anisotropic impedance surface (AIS) is used to increase the impedance bandwidth, such that the traditional quarter-wave monopole antenna’s bandwidth is increased based on the height reduction.

First, by loading a circular metallic disk on top of the monopole antenna, the profile of the antenna at the center frequency of 3 GHz is reduced from 25 mm (0.25 λ₀) to 15 mm (0.15 λ₀), where the disk diameter is 9 mm. The minimum sphere radius surrounding the antenna is reduced from 25mm to 15.66mm, which achieves a certain degree of miniaturization for the antenna. Then, a cylindrical AIS structure is added around the monopole, and the ideal impedance dispersion curve of AIS is obtained by the equivalent theoretical circuit model to control the response of the antenna at different frequencies. Its impact on the antenna’s input impedance is investigated. According to the ideal impedance dispersion characteristics, the realistic AIS structure is designed to expand the bandwidth of the miniaturized disk-loaded monopole antenna without affecting its radiation characteristics. The AIS-integrated broadband miniaturized antenna has a VSWRlt;2 bandwidth of 2.64-5.02 GHz, i.e. a ratio bandwidth of 1.90:1, and a stable omnidirectional pattern with a gain varying from 4.70 to 6.46 dBi in its operational band.

KEY WORDS: top-hat monopole, anisotropic impedance surface (AIS), miniaturization, wideband antenna

目 录

1 绪论 1

1.1研究背景和研究意义 1

1.2研究现状 2

1.2.1单极子天线研究现状 2

1.2.1天线小型化研究现状 3

1.2.2各向异性阻抗表面研究现状 4

1.3电磁仿真建模算法 5

1.4本文的工作 6

2 理论基础 7

2.1单极子天线的辐射原理 7

2.2各向异性阻抗表面的原理 8

2.3本章小结 9

3 圆盘加载的单极天线的研究 10

3.1天线模型 10

3.2尺寸参数对天线的影响 11

3.3设计实例 12

3.4本章小结 13

4 带有AIS的圆盘加载的单极天线的设计 14

4.1天线模型 14

4.2 AIS表面阻抗对天线VSWR的影响 14

4.3 AIS设计 16

4.3.1 AIS阻抗色散曲线的确定 16

4.3.2 AIS结构的设计 17

4.4结果分析 20

4.5本章小结 22

5 总结与展望 23

5.1全文总结 23

5.2研究展望 24

参考文献 25

致 谢 29

1 绪论

1.1研究背景和研究意义

天线可以通过无线信道在发射器和接收器之间有效地传播电磁能量。天线是连接近场和远场通信系统的重要设备，是雷达，声纳等系统的重要元素。

天线的历史长达一个多世纪，种类有上千种。天线领域是一个热门的研究课题，我们的重点放在单极子天线上，单极子天线体积小，重量轻，结构简单，全向性好，无论在军用通信还是民用通信系统都有广泛的运用。在电子和无线时代，天线工程师有责任不断改进天线技术和利用率，减少危险的电磁效应。

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