摘要 本論文提出一個利用電抗性負載元件來減小面積的雙頻槽孔天線，此天線設計應用於全球衛星定位系統(GPS L1 band：1.575 GHz)及藍芽傳輸(Bluetooth 2.4~ 2.484 GHz)的頻段上。 一般傳統常見的開路槽孔天線為四分之一波長共振的模式，其天線共振率是由槽孔的長度來決定。傳統開路槽孔天線是藉由一穿過槽孔的微帶線，以電磁耦合的方式饋入，而天線的特性阻抗可藉由調整槽孔的長度或寬度，亦可透過調整饋入微帶線的相對位置來控制。 本論文首先藉由在傳統單頻開路槽孔天線內部加入一負載電容，進而將原本需要四分之一波長的槽孔長度，有效縮小至八分之一波長以內，並提出在負載電容後端加入電感與基板接地面短路，而藉由調整電感感值，使共振頻率可以做微幅的調整；而天線特性阻抗則可藉由在饋入線末端加入一電感，與基板接地面短路，並藉由調整電感感值來達到良好的阻抗匹配。接下來，本論文提出在負載電容後端再加入一串聯電容，並使其與原本的電流路徑分流，以產生雙頻的電流路徑，達成共用槽孔的雙頻天線設計。本論文提出的電抗性負載型雙頻槽孔天線，可使用厚度為0.8mm的FR4基板，與市售晶片型被動元件製作。雙頻槽孔天線在低頻量測的共振頻率為1.575 GHz，其頻寬為1.555~1.595 GHz；高頻量測的共振頻率為2.450 GHz，頻寬2.400~2.500 GHz，而天線增益峰值在1.575 GHz為2.52dBi；2.4~2.485 GHz增益峰值在0~0.5 dBi之間。AbstractIn the thesis, a design of the dual-band slot antenna loaded with reactance is presented. The proposed antenna is applied for GPS (L1：1.575GHz) and Bluetooth (2.4~2.484GHz) applications. For a conventional open-end slot antenna, the operation frequency is mainly determined by the slot length, which is generally of a quarter wavelength. An open-end microstrip line is conventionally adopted to feed the antenna through electromagnetic coupling. Impedance matching for this structure can be controlled by the length of open stub, and the feeding position. In order to reduce the length of the slot antenna from a quarter wave-length to one- eighth the effective wavelength, we add a load capacitor inside slot. The inductor connected to the ground behind capacitor can be used to adjust the resonant frequency by using different value. Besides, antenna characteristic impedance is also tunable by using different values of inductor which is added at the end of the feed line connected to the ground plane. For dual-band antenna design, a series capacitor is adopted to branch a new antenna resonant current path. Therefore, the proposed dual-band antenna design is achieved in one slot. Antenna measurements regarding with the return loss, radiation pattern, and axial ratio are conducted for design validation. It is found that the simulation and measurement are in good agreement.
