天線為無線傳輸系統中相當重要的一個元件，它既為傳輸系統中發射端的最後一個元件，又為接收端的第一個元件。因此它的特性是我們必須確切關注的項目。而天線量測是天線成品製作完成時一個重要的步驟，他提供了天線成品最終的收發特性數據，因此量測的精準度不僅左右了我們對這支天線的性質判斷，也同時影響到我們對整體系統能力的評估。
天線量測時，找出相位中心(Phase Center)是提高量測精準度的一個主要方法。特別是波束成形公式的計算主要依賴於陣列天線(Antenna Array)中，各個子天線之間的相對位置，然而在陣列天線的製作過程中，每一個子天線都會因為製作上的誤差而造成微小的差異。對於一體成形的陣列天線來說，下列兩個因素都會對波束成形(Beamforming)產生嚴重的影響：一、各個子天線因為製作精度的問題，在製作完成時各個子天線的相位中心就已經產生了各自的偏移 ； 二、陣列天線中各個子天線之間的互耦合效應。由於以上兩個因素，使得子天線的相位中心位置不如預期，進而導致量測的相位與理論值產生了偏移。
在本論文中，我們會根據量測的相位場型(Phase Pattern)與模擬的相位場型利用相位場型曲線近似的作法，快速地找出每一根子天線的相位中心。而根據此方法，相位中心的誤差精度將不會受限於量測天線時的機台。

Antenna is a very important element in the wireless transmission system. It is the last element of transmitter and the first element of receiver. Therefore, we must pay attention to its characteristics. The antenna measurement is an important step after implementing the antenna and provides the information of transmitting/receiving characteristics. As a result, the accuracy of the measurement significantly not only influences our judgment on the feature of this antenna but also affects the ability to predict the performance of the overall system.
The major approach to improve the measurement accuracy is finding out the phase center as precise as possible when one measures the antenna. Especially for the antenna array, the beamforming function strongly depends on the relative displacements of the antenna elements with respect to each other. However, each array element slightly differs from the other ones during the manufacturing process of the array. For the antenna array integrally formed, the following two factors have serious impacts on the beamforming: 1. Due to the fabrication tolerance, the phase center of each element possesses its own offset; 2. Mutual coupling effects between the individual array elements. On account of the abovementioned two factors, the phase centers of array elements are not as expected thereby causing the translational phase shifts deviating from the theoretical ones.
In this thesis, based on the measurement and simulation of phase patterns, the curve fitting approach can quickly identify the phase center of each array element and the accuracy will not be limited by the mechanical positioner.

第一章 序論 1
1.1研究動機 1
1.2論文架構 3
第二章 陣列天線之網路模型 5
2.1 陣列天線之S參數模型推導 5
2.2 陣列天線總輻射功率與輻射強度之S參數模型推導 13
2.3 陣列天線實際增益之S參數模型推導 14
2.4實際增益之S參數模型模擬驗證 15
第三章 用於陣列天線場型量測之全波模擬輔助相位中心校正法 19
3.1待測天線擺置位置偏離相位中心之影響 19
3.2全波模擬輔助之相位中心校正法 24
第四章 量測結果 34
4.1 子天線之量測結果 34
4.2 相位中心校正法之校正結果 40
4.3波束成形結果 41
4.3.1 主動單元場型量測法與直接利用威爾京森功率分波器之波束成形結果 42
4.3.2 主動單元場型量測法於待測天線量測擺放異動之波束成形結果 50
第五章 結論 52
5.1 結論 52
5.2 未來研究與改進方向 52
參考文獻 53

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