可適性寬頻陣列多重波束成型技術

Abstract

透過調整權重，可適性天線陣列能夠同時接收特定方向的信號並消除其他方向的干擾信號及雜訊。然而，當天線陣列遭受非理想效應的影響時，效能將大打折扣。在本論文中我將討論兩種非理想效應：天線元件位置擾動以及交互耦合現象，在寬頻一維天線陣列及寬頻圓形天線陣列以及廣義旁瓣濾波器架構的寬頻圓形天線陣列架構下所造成的影響，並提出有效的解決方法。 本論文使用改良式寬頻雜訊子空間投影法來修正非理想效應的問題，此方法透過特徵分解寬頻信號的頻譜密度矩陣(Spectral Density Matrix)，再以限制目標函數梯度法疊代修正天線陣列的指引向量。為了評估效能，本論文以實驗模擬，比較改良式寬頻雜訊子空間投影法和對角線負載法以及最佳對角線負載法的效能。

By adjusting weights, adaptive antenna array can suppress interference and noise while receiving a signal from a specific angle. However, the performance of antenna array may be highly degraded if there are uncertainties in array. In this thesis, we consider some uncertainties including array element position perturbations and mutual coupling effects. We focus on correcting these effects when using broadband uniform linear array, broadband uniform circular array, and GSC. In this thesis, we use broadband noise-subspace projection method to correct the problem caused by the uncertainties. In this method, we use the eigen-decomposition of spectral density matrix and a gradient method to update the steering vector of antenna array iteratively. According to the simulation results, our method performs better than Diagonal Loading and Optimum Diagonal Loading.