本論文以設計一應用衛星定位系統(GPS)之天線，一般衛星訊號接是以圓極化的方式來接收避免多重路徑反射的干擾以及法拉地旋轉的效應，操作頻帶主要以能覆蓋於L頻帶(1 GHz~2 GHz)中的GPS頻率為主。槽孔天線一般被廣泛應用在寬頻的圓極化的設計上，由於共面波導饋入的槽孔天線有其令人著迷的優點，像是寬頻，易於製作，簡單的單面結構，加入擾動結構能有效的產生圓極化，因此一開始我們採用了閃電型共面波導的饋入線，並在其左方空白處加入一個大與一個小的擾動結構設計出一S11與AR頻寬皆大於60%之天線。
由於槽孔天線雙向幅射的特性，在使用上較常考慮到向上的部分，因此為了抑制向下輻射提高上方增益，通常是在天線的下方距離四分之一波長處放置一反射板，而本論文提出的則是在反射板四周的邊牆上挖槽與在其上方貼上金屬貼片，將天線與反射板距離縮減到十六分之一波長來達到低剖面之設計。透過此反射板，可抑制背向輻射10 dB以上，提高增益至少3 dB，而本天線主要設計在L頻段(1 GHZ ~ 2 GHz)，最後透過實作與量測得出與模擬有相符的結果。

In the thesis, designs of wideband circularly polarized slot antenna which covers the L band (1 GHz ~2 GHz) for Global Positioning System (GPS) applications are proposed. The coplanar waveguide (CPW) fed printed slot antenna has many desirable features like wide bandwidth, ease of fabrication, compact uniplanar configuration, increased freedom for applying perturbations and generating circularly polarization quite efficiently. First we use the Lightening-Shaped feedline and add the perturbation structure at the left side of the slot to design a wide band circular polarization slot antenna. It is found that -10-dB S11 bandwidth and 3-dB axial ratio bandwidth of the antenna are both over 60%.
Slot antennas are generally of bidirectional radiation. In order to achieve the unidirectional radiation, it is usually to apply a ground-plane reflector which is 0.25λ_0 under the antenna. In the thesis, we decrease the height to 0.0625λ_0 by add the slot around the side wall and metal patches around the cavity, and the low profile design has been achieved. With the back cavity, more than 10-dB in front-to-back ratio and more than 3-dB increase in the peak gain haven been obtained, at the price of the decrease in the axial ratio bandwidth.

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