本論文提出一個雙饋入微帶線的雙頻環形槽孔天線設計，並且在低頻產生圓極化的效果。文獻上，傳統的微帶線饋入的環形槽孔圓極化天線，大都需要改變槽孔形狀或者加入額外電路與集散元件來使環形槽孔天線產生圓極化。本文中先以傳統雙饋入微帶線的環形槽孔天線為基礎，接著觀察雙饋入末端在不同情形的電場分布，最後得到雙饋入末端當左邊為開路右邊為金屬片時，環形槽孔產生逆時針方向流動的電場。之後對雙饋入微帶線作一系列的參數探討，當雙饋入的右邊相位領先左邊相位為約85度時，則會有良好圓極化天線。且當雙饋入相對距離固定時，可以任意變換微帶線饋入位置不會影響圓極化天線的特性。之後在環形槽孔所圍繞的金屬增加0.5λ的槽孔，藉由環形槽孔在高頻的電場特性，透過電感耦合的方式使0.5λ的槽孔來產生共振，而且不會影響到原本圓極化的特性。本論文雙頻槽孔天線式設計在GPS(L1：1.575 GHz)與藍芽頻段(2.4~ 2.484 GHz)，使用厚度為0.8mm的FR4基板。GPS環形槽孔天線的量測的共振頻率為1.575 GHz，其頻寬為1.54~1.635 GHz，軸比頻寬為1.5625~1.5825 GHz，在1.575 GHz軸比為1.04 dB，軸比頻寬內的增益有0.1~0.9 dBic。雙頻環形槽孔天線在低頻量測的共振頻率為1.575 GHz，其頻寬為1.545~1.625 GHz；高頻量測的共振頻率為2.435 GHz，頻寬2.4~2.485 GHz；軸比頻寬為1.565~1.5875 GHz，在1.575 GHz有最小值為0.30 4dB；軸比頻寬內的增益約為0.4~1.1 dBic之間，2.4~2.485 GHz增益在2.5~4.2 dBi之間。此量測與模擬結果比較後具有良好的一致性。In the thesis, a design of the dual-band antenna with dual feed and ring slot is presented. The proposed antenna is applied for GPS (L1：1.575GHz) and Bluetooth (2.4~2.484GHz) applications. While the proposed antenna is linearly polarized at 2.4 GHz for Bluetooth applications, it is circularly polarized at 1.575 GHz for GPS systems. In the operation of circularly polarized radiation, the slot is fed by two microstrips. One of the microstrip is open, and the other is terminated by square patch. The electric field of in the ring slot is traveling counterclockwise which results in circularly polarized radiation. This result is not affected by the position of dual feeds. The parasitic 0.5λ slot resonating at 2.4 GHz is responsible for the radiation at 2.4 GHz. With the presence of the parasitic slot, the circular polarized radiation is hardly affected. Antenna measurements regarding with return loss, radiation pattern, and axial ratio are conducted for design validation. It is found that the simulation and measurement are in good agreement.
