臺灣博碩士論文加值系統

四波束切換式天線系統為智慧型天線的一種，其結構包含了陣列天線與波束形成器兩大部分，其原理是產生4個波束來覆蓋120度扇形區域，藉此來提高系統載波干擾比和系統的頻率複用率。

在陣列天線部分，我們使用具有製作容易、成本低、低姿勢等優點的 矩形微帶陣列天線，其元素間距為半波長。在波束形成器部分，吾人在論文中提出一種創新的四波束形成網路，此為一種具有低旁瓣位準的 巴特勒矩陣，其由 巴特勒矩陣與四個 相位差的不等功率分配器所組成。此種改良式的 巴特勒矩陣不但簡化了 巴特勒矩陣電路的複雜度，並且維持了 巴特勒矩陣的波束要求與精確的輸出位準和相位的電路優點。由量測結果可知，此種改良式的 巴特勒矩陣可使天線端的旁辦位準有效地降低至-10 dB以下，且四波束的正向角誤差均在 以內。經由數學推導證明，此種電路設計方式亦可延伸應用至 巴特勒矩陣。

The switched-beam antenna is one type of the smart antennas, which consists of the antenna array and the beamforming network. The four-beam smart antenna generates four beams to cover a 120° area, which can be used to improve the carrier-to-interference ratio and the frequency reuse of a cellular system.

Due to the attractive features of microstrip antennas such as low profile, easy fabrication, and low cost, we use microstrip antennas as array elements. In this thesis, we propose a novel four-beam beamforming network which consists of a 4×4 Butler Matrix and four 180° power dividers. This network is able to provide low side-lobe level. A modified Butler Matrix not only simplifies the circuit of the 8×8 Butler Matrix, but also meet the requirement of the original Butler Matrix. From the result of measurement, the side-lobe level of each beam of the modified Butler Matrix is less than –10 dB. We also show that this method is applicable to any Butler matrix.

致謝 i
中文摘要 iii
英文摘要 iv
目錄 v
圖表目錄 vi
第一章 緒論 1
第二章 微帶天線分析與製作
2.1 微帶天線原理與特性 3
2.2 矩形微帶天線設計與分析 8
2.3 實際製作與量測結果 15
第三章 陣列天線理論與製作
3.1 陣列天線理論 18
3.2 低旁瓣陣列天線設計與分析 22
3.3 微帶陣列天線實作與量測 32
第四章 四波束切換式陣列天線設計與製作
4.1 巴特勒矩陣基本原理 35
4.2 巴特勒矩陣電路設計 42
4.3 四波束切換式陣列天線實作與量測 46
第五章 結論與未來研究方向 50
參考文獻 51

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