新型多天線系統分析

Abstract

在本論文中，我們提出了兩種新型關於多天線系統的電磁分析。第一項是天線空間相關係數(Antenna Spatial Correlation)的新型計算方法，第二項則是輻射效率(Radiation Efficiency)與匹配網路(Matching Network)的分析探討。論文中所有的討論驗證將以一對偶極天線與平版天線做為分析基準。 首先，我們分析過往天線空間相關係數表式方法，綜合比較發射端與接收端的異同，將各式方法截長補短後提出了一組接收端的新型態空間相關係數表式方法，此法借鏡發射端空間相關係數表示方式的特點，有別於傳統使用天線輻射場型而改用散射係數矩陣(Scattering Matrix)進行運算，又因散射係數矩陣的獲得與計算遠較天線輻射場型容易，達成大幅降低量測困難度與計算的複雜度的效果。 此外，我們探討了不同匹配網路與不同相位的饋入訊號在輻射效率上的行為，並定性定量的分析其成因，將其整理為一方便理解運算的公式。最後則運用微波電磁理論與數值技巧提出最佳化的匹配網路，除了求出其數值解外，也致力於研究其封閉公式解以降低其運算時間與提高方便性，並在各式實例中與傳統匹配網路進行效能比較與討論，以不同中心頻率、不同種類的天線與不同的應用技術驗證之。

In the thesis, we propose two new electromagnetic analysis strategies to evaluate the performance of multiple antenna systems. The first is a new antenna spatial correlation formula, and the other is a new analysis strategy of radiation efficiency and the matching network. All case studies are simulated using a dipole pair and a patch pair as the benchmark. First, we compare the spatial correlation formula of the receiver with the transmitter, and a new representation of spatial correlation formula is proposed. Replace of the radiation pattern, the formula of the receiver computes spatial correlation from the scattering matrix description of the antenna system. Because the scattering matrix is easier measured than the radiation pattern, this approximation formula can effectively reduce computation complexity and measurement difficulty. We further propose a new analysis strategy and physical meaning of radiation efficiency and the matching network. It evaluates how the radiation efficiency may change when the antenna ports excite signals with different phases. Besides, we also investigate how different matching networks influence the radiation efficiency, and then derive a formula to describe the relationship. Moreover, we provide a new matching network for optimum radiation efficiency by microwave theory and mathematical deduction, and then prove it by applying them in real examples.