準八木天線的改善研究和使用寬頻巴倫的新式寬頻偶極天線

Modified Quasi-Yagi Antennas and a New Type of Wideband Dipole Antenna with Broadband Balun

何國睿(Kuo-Jui Ho)

指導教授 ： 鐘太郎

國立清華大學/電機資訊學院/電機工程學系/碩士(2010年)

https://doi.org/10.6843/NTHU.2010.00532

摘要

本論文提出一個利用寬頻巴倫(balun)來實現一個新式寬頻偶極天線的架構，可用的頻帶可從1.7GHz~6.2GHz，包含了目前市面上所有通用的網路頻帶標準，即1.71GHz~2.69GHz(GSM1800、GSM1900、UTMS、802.11b、802.11g、802.11n、WiMax、LTE)，3.4GHz~3.69GHz(WiMAX)，5.15GHz~5.85GHz(802.11a、WiMAX)，且在主要頻帶的反射損耗(return loss)皆在-15dB以下。因為偶極天線是個平衡的輸出而輸入常常是用同軸電纜(coaxial cable)等不平衡的輸入，所以必須要利用巴倫來轉換傳輸。此寬頻天線利用微帶線(microstrip)到槽線(slotline)的轉換傳輸來傳送訊號及能量，並在輸入到天線的兩端電流創造出180度的相位差，即造成偶極天線電流同向的效果。此天線的場型在可利用的頻帶幾乎都呈現全向性(omni-directional)的結果，且增益在2dBi~5dBi之間，平均3.56dBi。本論文除了寬頻天線外，還模擬與實作準八木天線(quasi-Yagi)及改良它的巴倫頻寬。利用柴氏(Chebyshev)阻抗轉換器及槽線弧形截線(radial stub)去達到微帶線到共面槽線的轉換傳輸並達到寬頻的特性。除此之外還探討了阻抗匹配的問題，在一定的條件下可以加以利用把天線拆成兩部分設計。實作出的準八木天線主要操作頻帶，在目前所應用最廣泛的2.45GHz附近，除了巴倫頻寬改善外，增益表現及場型都與原本準八木天線相近。本論文希望能在無線網路用的天線提供些微的貢獻。

關鍵字

寬頻偶極天線 ； 準八木天線 ； 寬頻巴倫

並列摘要

This thesis proposed a new type of wideband dipole antenna with a wideband balun covering the bands almost from 1.7GHz to 6.2GHz. The proposed dipole antenna is fed in microstrip line and utilizes microstrip to slotline transition method to transmit power. For this dipole antenna, it can be used in all wireless network application including all WLAN and WiMAX bands. The novelty shape of this antenna is designed for more paths of current flows. The radiation patterns are approaching Omni-direction in all bands but the front end has higher gain. It is easy to fabricate because of using FR4 substrate and the gain performance of this antenna is 3.56dBi on the average. Not only design of the wideband dipole antenna is considered in this thesis, but also modification of quasi-Yagi antenna is investigated. The conventional quasi-Yagi antennas have some artifact, so attempts have been made to solve these problems by using the Chebyshev transformer and radial stub to achieve microstrip to coplanar stripline transition and to reach wideband performance. In this section，the impedance matching problems have been discussed，thus we can design antennas from two part through some conditions. The main frequency band is operating in nearby 2.45GHz that is the most popular band we use in wireless network today. With the results obtained, it is hoped that this thesis can make some contributions to the research of wireless networks.

並列關鍵字

wideband dipole antenna ； quasi-yagi ； wideband balun

參考文獻

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