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標題: | 應用於小型多輸入多輸出系統之阻抗匹配網路 Impedance Matching for Compact Multiple-Input Multiple-Output (MIMO) Systems |
作者: | Wen-Fong Tsen 曾文方 |
指導教授: | 李學智 |
關鍵字: | 多輸入多輸出,互耦合效應,阻抗匹配,系統容量,相關係數, Multiple-Input Multiple-Output (MIMO),mutual coupling,impedance matching,capacity,correlation, |
出版年 : | 2011 |
學位: | 博士 |
摘要: | 多輸入多輸出天線系統可以提供較高的頻譜使用效率,但是天線陣列中不同天線之間的相關性會嚴重影響系統的容量,這種情況在小型化多輸入多輸出天線系統中尤其嚴重。本論文主要係分析天線間耦合效應對於小型化多輸入多輸出天線系統之效能影響,並研究如何透過阻抗匹配的方式,提升整體系統容量。
首先,我們分析並比較一個具有2個發射及2個接收天線的小型多輸入多輸出系統的三項性能指標:(1)信號相關性(2)平均接收功率(3)系統容量。我們首先介紹天線耦合矩陣模型的前提假設,再透過耦合矩陣模型來分析系統之信號相關性與接收功率,並透過適當的功率與通道矩陣正規化,比較不同的阻抗匹配方式對於系統容量的影響。 接著,我們研究在僅考慮小型化多輸入多輸出系統的訊號耦合效應前提下,如何透過單埠匹配阻抗的選擇,以達到系統容量的最大化。我們利用阻抗矩陣分析一個小型化多輸入多輸出系統,接著透過最大化在高訊雜比時之系統容量,可以得到數個可以解出最佳化阻抗矩陣之聯立方程式。我們並證明輸入阻抗匹配為最佳阻抗匹配方式。 最後,我們進一步研究在同時考慮小型化多輸入多輸出系統的訊號及噪音耦合效應下之最佳化阻抗匹配方式。我們先介紹接收機的噪音模型,並計算同時具有訊號及噪音耦合的情況下之多輸入多輸出系統容量,接著透過最大化在高訊雜比時之系統容量,便可以得到最佳化匹配阻抗。 Multiple-Input Multiple-Output (MIMO) system offer very high spectral efficiency and link reliability. However, correlation of signals at different antenna element can considerably decrease the capacity of MIMO systems. Such correlation occurs particularly for compact MIMO systems, where the separation between antennas is small. This thesis focuses on the effect of mutual coupling on compact MIMO systems, and capacity improvement of compact MIMO systems by introducing matching networks between the receiving antenna array and the load termination. In the first part, we study three performance measures, i.e. signal correlation, average receive power and capacity, of a compact MIMO system with two transmitting-two receiving antennas. We begin in identifying the assumptions needed to rigorously derive the classical form of the coupling matrix. Using the coupling matrix, we investigate the impacts of coupling on the correlations and receive power. After introducing an appropriate method for power and channel normalization, the effect of matching impedance on the capacity of MIMO systems is addressed. In the second part, the optimal single-port impedance matching for capacity maximization of compact MIMO systems with signal coupling is derived. We begin in developing the complete framework including the mutual coupling effect using Z-parameters. By maximizing an upper bound of the ergodic capacity for a MIMO with coupling at the receivers in high SNR scheme, a set of equations is formulated to find the optimum solution when the MIMO. We also prove that input impedance matching is the optimum solution when the MIMO system operates in high SNR scenarios. Finally, we study the impedance matching problem in the presence of signal and noise coupling of compact MIMO systems. We begin in presenting a circuit model for a noisy MIMO receiver which includes arbitrary signal and noise coupling. After obtaining the MIMO capacity with spatially correlated noise, the optimum matching circuit in high SNR regime is derived. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/48333 |
全文授權: | 有償授權 |
顯示於系所單位: | 電信工程學研究所 |
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