不對稱共面波導饋入寬頻圓極化矩形環槽天線

Abstract

本論文提出一個應用於無線通訊系統之藉由不對稱共面波導饋入的寬頻圓極化矩形環槽天線。我們所提出的天線設計擁有結構簡單並且易於製造的特性。有別於一般常見的方形圓極化環槽天線，本天線的幾何形狀為矩形。不對稱的饋入結構和裁切過的底板會干擾底板電流分布，因此，矩形架構也能產生圓極化。阻抗匹配可藉由調整不對稱共面波導延伸出的訊號線長度來達成。 提出的天線有良好的左手圓輻射場型，主瓣朝著+Z方向，適當的調整天線參數可得到寬頻的特性。量測的軸長比具有28.6%的頻寬且完全落在阻抗頻寬之中，相較於其他圓極化環槽天線還更寬頻。 以上所提出的所有設計理論及天線架構的細節，模擬與實驗驗證，於本論文中都會加以仔細地討論。

A wideband circularly polarized rectangular slot loop antenna excited asymmetrically by CPW for wireless communication systems is proposed. The proposed design has a simple antenna structure and is easy to fabricate. The shape of the proposed antenna is rectangular, which is different from the conventional square circularly polarized slot loop antenna. With the asymmetric CPW feeding structure and the truncated ground plane, the current distribution on the ground plane will be interfered, thus the circular polarization can be obtained in a rectangular design. The length of the protruded signal line of the asymmetric CPW feeding structure can be adjusted for good impedance match. A left-handed circularly polarized radiation in the broadside direction of the antenna with wideband characteristic has been achieved by adjusting the parameters properly. The measured 3 dB axial ratio bandwidth is within the measured -10 dB impedance bandwidth and has a bandwidth of 28.6%, which is wider than other circularly polarized slot loop antenna in the literature. The details of the antenna design are discussed. Experimental and simulated results are also presented and discussed in the thesis.