利用可重構頻率選擇反射面實現2.45GHz之MIMO縮小化智慧型天線

Abstract

本論文提出利用可重構頻率選擇反射面實現2.45GHz之MIMO縮小化智慧型天線，可應用於無線基地台（Wireless Access Point, WAP），操作頻率為2.4 GHz ~ 2.5 GHz的Wi-Fi頻段，輻射效率為40% ~ 70%，天線所放置的基板大小為120 mm x 120 mm x 0.8 mm，實際所佔用的體積為120 mm x 120 mm x 12.3 mm，相對於中心頻2.45 GHz，亦即0.98λx 0.98λx 0.1λ。在設計上，結合了頻率選擇反射面之反射與輻射特性，並利用結構彎折的設計，可有效減少天線的占用體積，卻又彼此不相干擾。此外，本天線可透過一分多切換式饋入網路獨立切換每一路反射面之特性，以達到不同方向之輻射場形，並針對不同方位之使用者提供最佳訊號強度。 本論文也提出MIMO天線架構，當天線所放置的空間環境多樣或是室內環境存在立柱、家具等大型障礙物時，可配合演算法判斷何種切換反射面之組合最利於當前使用者的通訊，並突顯此天線在各種空間上的極高適應性與靈活性。

In this thesis, a miniaturized smart MIMO antenna using reconfigurable frequency selective reflectors is proposed. This antenna can be applied to Wireless Access Point. The operating frequency is 2.4GHz to 2.5GHz in Wi-Fi band and the radiation efficiency is 40% ~ 70%. The size of substrate is 120mm x 120mm x 0.8mm, and the actual antenna size is 120mm x 120mm x 12.3mm, compared to the center frequency of 2.45GHz, is 0.98λx 0.98λx 0.1λ. The combination of the reconfigurable frequency selective reflector’s characteristics between reflection and radiation is designed to reduce the occupied area of the smart antenna unit and the performance of smart antenna unit is not affected by each other. In addition, this antenna can display different radiation patterns by using one to multipath switching feeding network to change each reconfigurable frequency selective reflector’s characteristic, and offer the best signal strength according to the position of the user in different directions. In this thesis, the design of the MIMO antenna structure is also proposed. The smart MIMO antenna can judge the best switching combination of the reconfigurable frequency selective reflectors with algorithm in communication, if the antenna is installed at indoor environment existing big obstacles like pillars, furniture, etc. With this advantage, the smart MIMO antenna has higher abilities about adaptability and flexibility.