耦合效應對於來波方位估測演算法影響之評估與解決方案

Abstract

本論文探討來波方位估測演算法(Direction of Arrival Estimation Algorithm)特性受影響之因素，包括接收高相關度訊號與天線耦合效應，通過使用電磁模擬軟體CST與Matlab進行模擬，試圖還原真實狀況下之效應。在論文中採用28GHz韋瓦第天線(Vivaldi antenna)作為陣列接收天線之接收單元天線作為例子模擬。 嘗試解決天線耦合效應使訊號方向估測演算法特性下降問題時，首先採用接收模態耦合矩陣校正，校正後之特性上升在模擬結果上是十分顯著的，但卻遭遇另一個問題，訊號來波方位接近陣列天線端端射方向時之校正失效。 為了解決此問題，我們提出另一種能夠校正大角度偏離陣列天線垂射方向之校正方式-逆真實指向矩陣校正，該校正方法可以具有更高精度的來波方位估測。但是此校正模型問題在於，此校正方法校正後之精準度越高，校正範圍就越窄，必須對於模擬條件做出適當的權衡。 最後我們使用以上兩校正方法設計出分段來波角度校正方法，以達成在大範圍接收方向均能有精準的來波方位估測。

In the thesis, we discussed the effect that might affect the direction of arrival estimation algorithm, including receiving high correlated signal and mutual coupling effect, the simulation is carried out by using the electromagnetic simulation software CST and Matlab to try to restore the real condition. Theoretical and simulation on 1×8 Vivaldi antenna array were obtained as an example. In the first attempt to solve the problem that mutual coupling effect reduces direction of arrival estimation accuracy, we use receiving mode mutual coupling matrix correction. After the correction, the direction of arrival estimation accuracy has significantly improved, but the simulation encounters another problem, the correction failure when receiving signal direction near antenna array's end-fire direction. To solve this problem, we proposed another correction method “inverse real steering-vector matrix correction”. This correction method can have a higher precision direction of arrival estimation. The higher the precision after correction, the narrower the correction range will be, we need to make the appropriate trade-off. Finally, we designed the method of segmented angle correction using the above two corrections method, and the method has been reached in a wide range of receiving directions and high precision direction of arrival estimation.