本論文利用步階式阻抗共振器，設計出微小化準八木天線，其結構包含了導向器、步階阻抗的偶極天線、步階阻抗的反射器與截剪接地面。主要是探討各參數對天線的影響，包含了各元件的尺寸、元件與元件之間的間距與步階式阻抗共振器的選擇，並簡化設計流程。所設計的準八木天線因利用步階式阻抗共振器，可有效地縮小電路面積且維持一定的天線增益，在不嚴重影響天線增益的情況下，步階阻抗偶極天線相較於傳統的偶極天線可大幅度地縮減27.5%的尺寸，以及可維持天線增益變化在2.6–4.2 dBi之間，在應用於無線區域網路(WLAN) 802.11 b/g的頻段中，可獲得大於10 dB的前後比(front-to-back ratio)，同時，適當地調整轉接器的尺寸與距離，讓10 dB頻寬可達到28%。所有的設計流程與量測模擬結果皆有詳細的討論於本論文中。In this thesis, stepped-impedance resonator (SIR) is used to design a compact quasi-Yagi antenna. The proposed antennas are composed of director, stepped-impedance dipole antenna, stepped-impedance reflector, and the truncated ground plane. The goal is to research on how each parameter affects the antennas performance, including elements’ dimensions, the distance between the elements, and the choice of the resonator. Meanwhile, the design procedure is outlined clearly in the thesis. Owing to the SIR, the proposed antennas can effectively miniaturize the circuit size and maintain as approximate the antenna gain as the conventional one. Without degrading the antenna gain severely, the stepped-impedance dipole antenna shows 27.5% length reduction in comparison to the conventional uniform half-wavelength one. Furthermore, the measured gain variation is of 2.6–4.2 dBi. Front-to-back ratios are better than 10 dB in the operating band of WLAN application 802.11 b/g. The transition (Klopfenstein Taper) can be adjusted properly to obtain a measured 10-dB return loss bandwidth of 28%. All of the design concepts, simulated results, and measured results are presented and elaborated clearly in the thesis.
