應用於無線區域網路之近距離多輸入多輸出雙頻天線

Abstract

本論文中，提出對於多輸入多輸出雙頻天線的設計方法，以應用於802.11 n之2.4 GHz與5 GHz頻段。天線是利用兩種不同頻率之諧振器互相耦合，使此天線在兩個頻段同時匹配來達到雙頻的效果，而天線雙頻的共振機制分別為操作在低頻的四分之一波長之寄生元件與操作在高頻的倒L 形單極天線；靠著彼此的互相耦合，使得此雙頻天線只需要一個饋入電路即可達到雙頻的目的。天線架構雖然是印製在印刷電路板上，但其尺寸不大，相鄰之兩空間13 × 5.5mm2 (0.104λ0 ×0.044λ0) 和18 × 6.5mm2 (0.144λ0 × 0.052λ0)分別放入天線1與天線2 (λ0為2.4 GHz在真空中之波長)。將天線1固定，探討天線2受到天線1的影響，從電容性耦合、電感性耦合以及地上之電流三個方面來切入研究，將兩者之耦合量降低以達到較好的隔離度。最後提出的架構，兩埠之間距離約為13mm (0.104λ0)，低頻隔離度為8.09dB高頻隔離度為12.65dB，模擬與量測結果一致符合無線區域網路需求。

In this thesis, a design method for the MIMO (Multi-input Multi-output) antenna structure for 2.4 GHz and 5 GHz applications is proposed. This structure utilizes two types of resonators coupled to each other to achieve the dual-band application. One is the conventional inverted-L monopole for higher operating band, and the other is λ/4 resonator for lower operating band. Since the two types of resonators couples to each other, this antenna structure only needs one feeding network for dual-band operation. This antenna is fabricated on PCB board, and the total spaces for antenna 1 and antenna 2 are 13×5.5mm2 and 18×6.5mm2, respectively. To achieve good isolation, we can investigate the interaction between antennas in three aspects, capacitive coupling, inductive coupling, and the surface current in the ground plane. The measured isolation of the proposed antenna with port distance of 13mm is 8.09dB in lower band and 12.65dB in higher band. The simulated and measured results come to an agreement.