應用於無線網路之波束切換天線設計與實現

Abstract

本論文提出以單極天線陣列實現波束成形及轉向控制的新型波束切換天線。天線操作在2.4GHz波段，單極天線及地面的天線組成，均使用FR4線路板製作而成。天線中，一主動天線位在天線地面中心，由寄生天線圍繞四邊，經由寄生天線開關切換組成直角邊角反射器用於波束的形成及90度轉向。天線在不同的設計參數加以模擬，歸納得出此天線實作的建議數據，並根據此實作建議提出一傳輸線開關切換寄生天線，減少天線的開關數量及簡化波束切換控制方式。 依模擬結果所得出的實作建議數據進行具有寄生天線開關及傳輸線開關等兩種形式天線製作，將天線的RF開關的開閉動作直接以斷路或短路替代，對這些具有理想化開關的天線進行量測與模擬數據比對，驗證波束切換天線結構設計及實作建議數據的可用性。實際以PIN二極體及GaAs開關等不同RF開關做為寄生天線開關以驗證RF開關功能，從量測數據得出的結果，所用RF開關的雜散寄生阻抗及隔離損失均會使天線性能劣化，尤其開關在開路狀態下的影響。接著實際應用RF磁簧開關在傳輸線開關的切換時，其量測結果驗證傳輸線開關提供更簡化且更好的切換控制特性。

A novel multi-beam switched parasitic antenna capable of beam forming and steering based on an array of monopole antennas is proposed in this thesis. The antenna operates at 2.4GHz band and all the monopoles and ground plane of antenna are made of FR4 PCB. In the antenna, one active element is fixed at the center of ground plane and squarely surrounded with parasitic elements which are switched as right angle corner reflectors for beam forming and 90-degree steering. The antenna is simulated with various design parameters to optimize and derive the antenna implementation data. Then, a transmission line switch used to switch parasitic element is proposed based on the implementation data for decreasing RF switches in the antenna and simplifying the multi-beam switch control method. Two type of antennas with parasitic switches and transmission line switches are implemented in accordance with the antenna implementation data derived from simulation results, and antenna RF switches are set short or open ideally instead of on/off action. These antennas with ideal switches are measured and compared with simulation results to justify the feasibility of the antenna configuration and implementation data. Practically utilizing various RF switches like PIN diodes and GaAs switches as parasitic switches to justify RF switch functions, and the derived result from measurements is that the stray impedance and isolation loss of RF switch deteriorate the antenna performance, worst in the off switch state. Then, practically utilizing RF reed switch in transmission line switch, the antenna measured results validate the transmission line switches to provide simpler and better multi-beam switch control characteristics.