寬頻圓極化槽孔天線 ; Wideband Circularly Polarized Slot Antenna

圓極化天線近年來被廣泛探討及應用，由於具有抑制干擾及降低多重路徑反射的特性，被普遍應用在無線通訊系統中。而許多不同實現的圓極化天線的設計陸續被提出，其中以共面波導饋入式的圓極化槽孔天線比較受到關注，因為具有寬頻、結構簡單、低成本、容易和其他主動元件作整合的好處。 本文中提出一種以非對稱共面波導饋入式的寬頻圓極化槽孔天線，非對稱地饋入的目的主要是想去微擾接地面上的電流分布，天線結構可以看成是將共面波導的訊號線饋入的平面和接地平面彎曲形成類似兩個迴圈。在共面波導傳輸線上加上串聯等效電路去做阻抗匹配，經由適當地去調整整個天線的參數，將可以達到寬頻圓極化的效果。 基於前面的設計概念，我們提出另一隻由微帶線饋入的寬頻圓極化槽孔天線，天線的外觀類似前面的設計，饋入位置選擇在電路板的邊緣，由於微擾結構使得電流分布能達到產生圓極化的條件。此隻天線的效能比起前者，具有更好的效能及更少的設計參數。 以上所提出天線具有良好的左手圓極化輻射場型，主瓣朝著+Z方向，且具有足夠頻寬以應用在無線通訊上且有抗雜訊效果，更進一步的模擬，實驗結果將在論文中仔細探討分析，以更了解此天線特性。 ; An asymmetrical CPW-fed slot antenna with wideband circular polarization is proposed. The antenna has an asymmetrical feeding for the purpose of interfering with the current distribution on the ground. The antenna geometry is the combination of ground loop and signal loop. Besides, the CPW transmission line is attached with series stubs for impedance matching. By adjusting the parameters properly, a wide circular polarization operation bandwidth has been achieved. Based on the above concept, A wideband circularly polarized antenna fed by a microstripline is also presented. It has the similar structure as the previous design and is fed from the edge of the substrate. Due to the perturbation configuration, a wide circular polarization bandwidth has been obtained. In this design, it has better performance and less design parameters. Both antennas have good LHCP radiations in the broadside direction. Moreover, the bandwidth is wide enough to mitigate the effect of interference in wireless communications. Design procedures, simulations, experiments are discussed and presented in the thesis.