使用不同散射相位平面金屬散射單元之被動全向性毫米波散射陣列面

Abstract

5G毫米波之訊號在傳送時有著易被障礙物阻擋導致通訊盲區產生之問題，而本論文利用二維相位陣列天線理論與波束成形之概念，使用擁有不同反射係數相位之金屬單元製作而成的反射陣列面來實現全向性散射，本反射面不需主動及控制電路便可利用全向性散射之特性，使訊號散射到室內因遮蔽物或角落造成的通訊盲區，以改善訊號的接收範圍。 本論文介紹一種反射係數相位隨金屬貼片尺寸變化之單元結構，利用此結構來設計有特定波束方向之天線單元，再來介紹光柵波瓣以及其合成的方法，使不同天線單元間之光柵波瓣與零點互補，加強天線單元間場型的能量均勻程度，之後將不同天線單元合併成一反射陣列面，完成其全向性散射的功能。並提出使用機率密度函數及累積分布函數做為評估散射能量均勻程度的指標，也根據雷達方程式來估算此反射陣列面在不同方向的散射功率，並與實際量測結果進行比較。 而實際的量測系統包含下列幾個項目：兩個操作頻率在28GHz的號角天線做為發射端天線與接收端天線、功率感測器、訊號產生器、電控旋轉台還有本論文所設計之反射陣列面，並驗證本論文所設計之反射陣列面與前人設計之散射陣列面，在不同角度時之功率散射情形。量測結果與模擬分析之結果大致吻合，並且在與前人使用相同大小金屬單元所設計之散射陣列面相比，在原本反射角的能量聚集處，有5dB左右的減少量，同時在其他方向也有相近的散射效果。

5G millimeter wave signals are easily blocked by obstacles, resulting in communication dead zones. This thesis utilizes two-dimensional phase array antenna theory and beamforming concepts to achieve omnidirectional scattering by using reflective array surfaces made of metal units with different reflection coefficients. This array do not require active and control circuits. Signal can be scattered to the indoor blind areas caused by walls or corners to improve the signal reception. Different reflection phase is realized by metal patch of different size. The grating lobes and the zero point between different antenna array are complementary to distribute the energy uniformly. Different antenna array are combined into a reflective array surface to accomplish omnidirectional scattering. The probability density function and the cumulative distribution function is used to evaluate the scattering energy uniformity, and to estimate the scattering power of the reflecting array surface in different directions according to the radar equation. Measurement results show good agreement with RCS simulation by Ansys HFSS. The measurement system consists of two horn antennas operating at 28 GHz as the transmitter antenna and the receiver antenna, power sensor, signal generator, rotator, and two types of reflective array. The scattered power observed from different direction from two types of proposed scattered surfaces are compared with previously proposed equal size metal scattering surface. 5dB RCS reduction in the radial direction is observed as compared with previous proposed scattering surface. Similar scattering intensity is observed as compared with previous proposed scattering surface.