使用反射相位控制微帶天線與最佳化之方法實現被動式電磁散射陣列面設計

Abstract

為了解決 5G 毫米波在傳輸過程中容易受到障礙物遮蔽，進而產生通訊死角的問題，本論文提出一種基於相位陣列天線理論、最佳化分佈反射單元相位的方法，利用相同貼片與共用地但饋入微帶線長度不同的微帶天線單元組成的陣列面，賦予每個單元具備相似散射大小，但散射相位不同，進一步地實現全向散射。該散射面無需任何主動元件或控制電路，即可將訊號反射至因遮擋或轉角所產生的室內外通訊死角，進而提升整體通訊覆蓋範圍。 本研究利用電波訊號在不同長度的傳輸線中傳遞時，走過的電氣長度不同的現象，來實現「連接不同長度微帶線的貼片天線單元被平面電磁波入射時能表現出相異的雷達散射截面積之相位」。此外，本論文亦運用 MATLAB 程式設計基因演算法，找出最適當的單元相位，以生成最終的陣列配置，有具波束成型反射陣列面以及具均勻化反射陣列面兩款陣列。對於波束成型陣列，驗證本論文提出的設計，可控制主波束在(θ,φ)=(30°,45°)。對於具均勻化散射陣列，本論文提出的設計在不同入射波之入射角度下較其他研究提出的陣列更高的平均反射能量與極值數量上的抑制。 藉由量測，驗證本研究提出的反射陣列面在不同入射與觀測角度下的功率散射表現。根據量測結果顯示，實驗資料與模擬分析結果大致相符，且對具均勻化散射陣列來說，在原本主反射角方向的能量集中處有一定量的減弱，同時在其他角度亦呈現相似的散射分佈趨勢，且有更高的平均反射能量。

To address the problem that 5G millimeter-wave signals are prone to blockage by obstacles during propagation, resulting in communication blind spots, this thesis proposes a method based on phased array antenna theory and an optimized phase distribution of reflective elements. The proposed array surface is composed of microstrip antenna elements with identical patch and common ground dimensions, while different microstrip feed line lengths are employed. This design enables each element to exhibit a similar scattering magnitude but different scattering phase responses, thereby achieving omnidirectional scattering performance. Without the need for any active components or control circuitry, the proposed scattering surface can redirect signals into indoor and outdoor communication blind zones caused by obstructions or corner effects, effectively enhancing overall communication coverage. This study exploits the phenomenon that electromagnetic waves experience different electrical lengths when propagating through transmission lines of different physical lengths, enabling patch antenna elements connected to microstrip lines of varying lengths to exhibit distinct radar cross section (RCS) phases. In addition, a genetic algorithm implemented in MATLAB is employed to determine the optimal element phase distribution, resulting in two array configurations: a beam-steering reflective array and a uniform scattering array. For the beam-steering array, the proposed design allows precise control of the main beam direction at (θ,φ)=(30°,45°). For the uniform scattering array, the proposed design demonstrates higher average reflected energy and power suppression of extreme scattering peaks under different incident angles when compared with previously reported arrays. Experimental measurements are conducted to validate the scattering performance of the proposed reflective array under various incident and observation angles. The measurement results show good agreement with simulation results. For the uniform scattering array, a noticeable reduction in energy concentration at the radial reflection direction is observed, while similar scattering distribution trends are maintained at other angles. Furthermore, measurement results obtained from combined four beam-steering array panels demonstrate a stronger main beam than a single panel.