超寬頻天線

Abstract

一般的洩漏波天線具有高增益、高輻射效率、低成本等優點。在本論文前面部份中提到，我們將研究寬頻第一高階模洩漏波天線。我們使用以微帶線設計非平衡-平衡電路來激發第一高階模。 反向平衡式微帶線是利用平衡式微帶線結構而將基板上下之正負訊號位置對掉而得到。此反向平衡式微帶線跟平衡式微帶線結合使用則能形成兩對寬頻之非平衡-平衡電路，並用來當寬頻洩漏波天線之基本饋入結構。 根據微帶線之第一高階洩漏波特性，本文討論不同的緩變方式來設計寬頻緩變洩漏波微帶天線。而此寬頻緩變洩漏波微帶天線反射損耗的量測結果，可以看到反射損耗小於-10dB的頻寬從3.5GHz至超過11GHz，相對的頻寬約3:1。 本論文後面部份提到，一種新式平面印刷式超寬頻天線(Ultra-Wideband Antenna,UWB Antenna) 其頻率操作在3.1GHz~10.6GHz。此種天線的結構為火山型(Volcano Smoke)的形狀。他們的結構都是建立於印刷式單極天線的基礎，具有超寬頻的特性、全方向性的場型、易於製作、輕量化及低成本。 論文中也提到在5.15GHz~5.825GHz為WLAN(Wireless LAN)的頻段，使用一H型的槽孔來達到共振原理並控制其反射損耗在該頻段造成帶拒的效果。

Generally, leaky wave antennas have some advantages: high gain, high radiation efficiency, low cost. In this thesis, we study the first higher order mode broadband microstrip leaky-wave antennas. We will implement the first higher order mode leaky wave antenna by the broadband balun. The inverted balanced microstrip line structure is developed from the balanced microstrip line. The position of the positive strip on the upper substrate side is exchanged with that of the negative strip on the lower substrate side by the method proposed in this thesis. United with the balanced microstrip line, this inverted balanced microstrip line can be used to form into a pair of broadband baluns. Using this broadband balun can realize a broadband leaky-wave antenna. Based on the characteristic of the first higher order leaky-mode for the microstrip antenna, this thesis proposes some different schemes to design the tapered profile of broadband tapered microstrip leaky-wave antenna. The measured bandwidth of the tapered microstrip leaky-wave antenna has a return loss less than -10dB from 3.5GHz to 10.5GHz, yielding a relative bandwidth of 3:1. In this thesis, we also study a novel ultra wide-band(UWB) planar printed antenna that operates from 3.1GHz to 10.6GHz which is proposed in this thesis. The configuration of this antenna is volcano smoke shape. The structure of this antenna is based on the planar printed monopole antenna. It has wideband characteristic, omni-directional pattern and ease of construction. In this thesis, we use a H-shape slot to implement a notch from 5.15GHz to 5.825GHz which is the operating frequency of WLAN(Wireless LAN).