12.5GHz 左右圓極化陣列天線之研究

Abstract

本論文主要討論Ku頻段左右圓極化天線陣列,應用在衛星電視通訊上,傳統的衛星天線在尺寸以及外觀很不實用,只能應用在固定式的場所,現在的車用通訊系統很發達,我們想把衛星電視應用在行車系統,所以我們需要適合的天線在尺寸以及外觀都能符合車子的需求,所以我們才會設計這種天線.我們由原先設計的單饋入傳輸線左右圓極化陣列天線,其需要兩組接收射頻電路,因為左圓極化跟右圓極化的饋入點太遠了所以沒辦法接在同一組射頻電路上,這是單饋入傳輸線左右圓極化天線陣列的缺點,為了解決這個缺點,因此雙饋入傳輸線左右圓極化天線陣列,如此一來就可以共用一組射頻電路,然後採用開關設計,就可以同時接收左右圓極化在一個射頻電路下完成,不過在設計採用雙饋入傳輸線左右圓極化天線陣列,遇到了圓極化不良的問題,一般來說好的圓極化天線,圓極化比最好要有3dB以下 ,所以我們設計了耦合器,可以改善圓極化比的問題,在之後的章節裡,我們會對所設計的天線,做詳細的討論

In this thesis, a satellite array antenna which operated at 12.2~12.7GHz has been developed. We design left-hand and right-hand circular polarization antenna arrays with single feed line. The disadvantage of this antenna is that the feeds of left-hand and right-hand circular polarization are too far, then the system needs two receivers. We have to use two RF-modules for receivers. Two receivers should be combined, so we improve this design. We use left-hand and right-hand circular polarization antenna arrays with dual feed line. Although receivers are combined , the antenna’s axis ratio is larger than 3 dB. The reason is that the power will couple from one microstrip line to the other one. In order to improve antenna’s axis ratio, we have to decouple the power. We will discuss the antenna’s structure, theory and how to decouple the power in this thesis.