八木天線（Yagi antenna）是一種高指向性天線，擁有結構簡單、易於製作及高輻射增益等特性。平面天線不同於傳統波導管等3維天線的設計，而是將輻射天線設計於平面PCB板上，體積小。而陣列天線則是利用每個單支天線產生的輻射場，以相位疊加方式增強在特定方向上的輻射功率，並減少在其他方向上的輻射，進一步加強天線的增益及指向性，減少電磁場在鄰近空間的干擾。此特性即為目前5G通訊高效能、高數據吞吐量的天線特徵。本研究以平面交錯式八木天線結構為設計基礎，於平面微帶線上建構高指向性陣列天線。以1x4的線性排列方式組成陣列天線，分析陣列結構下的輻射增益與場型效能的變化，並且使用四路功率分配器改善陣列天線阻抗匹配。實際測量該天線，於2.4 GHz擁有9.92 dBi天線增益及12.27 dB指向性。本論文將探討此平面交錯式八木天線結構對陣列天線特性的影響。

Yagi antenna is a kind of high-directivity antenna, which has the characteristics of simple structure, easy fabrication and high radiation gain. The planar antenna is different from the design of 3-dimensional antennas such as traditional waveguide antenna, but the antenna is fabricated on the planar PCB board with small sizes. The array antenna uses the radiated field generated by each single antenna to enhance the radiated power in a specific direction and reduce the radiated power in other directions in a phase superposition manner. This further enhances the gain and directivity of the antenna. This kind of performance reduces the electromagnetic interference in space and exactly meets the requirement of the 5G communication for high-efficiency and high data throughput. In this study, the planar flip-flop Yagi antenna structure is used as the basis for constructing a highly directional array antenna. Forming an array antenna in a 1x4 linear arrangement is investigated in this study. A four-way power divider is utilized to improve the impedance matching of the array antenna. The results show that the antenna has an antenna gain of 9.92 dBi, and 12.27 dB directivity at 2.4 GHz. In this paper, the design process of the high-directivity array antenna of the planar Yagi antenna and the influence of each structure on the antenna characteristics will be described in detail.