中文摘要
本論文針對大型基地台天線中的雙極化共振子提出一種平面式架構，利用金屬柱連通交叉偶極天線雙臂及反射板，改善低頻段阻抗匹配不佳之情況，進而提升共振子操作頻寬。接著我們將共振子初步整合成陣列並探討其表現，由於天線陣列本身則需符合高隔離度、高前後比等規範，因此在設定間距排列為天線陣列後，我們進一步著手改善其波束前後比與雙埠隔離度。首先藉由反射板塑型結構減少背向輻射場量，提升天線之波束前後比。之後於天線陣列結構加入倒L形解耦器與負載調整導向器來降低透過反射板耦合至鄰近共振子上之表面電流，改善天線陣列之雙埠隔離度，在輻射體與解耦架構整合後，陣列本身仍可維持寬頻、雙極化、高輻射效率等特點。最後我們所設計完成的實驗原型，可使得天線陣列涵蓋2600MHz~3800MHz操作頻寬，雙埠隔離度達30dB以上，而波束前後比則可大於25dB。
Abstract
A planar broadband dual-polarized antenna element for base station applications is proposed. In order to enhance the impedance matching at lower frequency band, there are metal cylinders electrically connected to the crossed dipole arms and the reflector, respectively. In addition, we have integrated the structure into array and discussed the performance. The antenna array is required to perform high isolation and high front-to-back ratio. After arranging four antenna elements with a distance, we have tried to improve the front-to-back ratio and port-to-port isolation. First of all, by using beamforming reflector design for back lobe suppression, the front-to-back ratio can be improved. Moreover, inverted-L isolators and top-loading tuning director are inserted into antenna array structure, so that the coupled surface current on the reflector can be reduced and the port-to-port isolation can be improved. Finally, the antenna array integrated with the director and isolators still performs wide band, dual-polarized and high radiation efficiency. The proposed antenna array shows that wide operating bandwidth can be generated successfully to easily cover 2600MHz~3800MHz operating bands. Port-to-port isolation is better than 30dB and front-to-back ratio is better than 25dB.
關鍵詞(Key Words)
天線陣列 (Antenna array)
基地台 (Base station)
雙極化 (Dual-polarization)
雙埠隔離度 (Port-to-port isolation)
前後比 (Front-to-back ratio)
相關檔案: 寬頻高隔離度雙極化基地台天線陣列設計(全文)
