基於類表面電漿之相位梯度超表面於高頻地波雷達之應用

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Title:	基於類表面電漿之相位梯度超表面於高頻地波雷達之應用
Authors:	余炫霖;Yu, Syuan-Lin
Contributors:	電機工程學系
Keywords:	超表面;高頻地波雷達;Metasurface;High-Frequency Ground Wave Radar
Date:	2025-08-25
Issue Date:	2025-10-17 12:56:31 (UTC+8)
Publisher:	國立中央大學
Abstract:	常見的高頻地波雷達系統在實際應用上，常部署在岸邊(如沙灘)使用，但是其激發的地波常會因為沙灘和海水模態不匹配造成能量浪費與傳輸效率低落的問題。另外一個常見的問題則是部分能量洩漏到天空形成天波，並在被電離層反射後在接收端形成破壞性干涉，上述問題即為地波議題。本論文將解決部署在岸邊的高頻地波雷達系統所會遇到的地波議題，因此提出一種新的高頻地波雷達部署方式。以兩層基板加上金屬條構成相位梯度超表面並置放於岸邊沙灘上，發射端從正上方向下垂直入射超表面，超表面幫助電磁波耦合成地波並將地波傳遞到海水表面，以此解決模態不匹配的問題。同時大部分能量耦合成地波，形成天波的比例將減少，破壞性干涉的問題也能改善。本論文透過模擬，得到每個超表面單元所需的反射相位以及對應的尺寸參數，並以這些不同尺寸參數的單元設計出相位梯度超表面。相位梯度超表面會提供額外的波數，使得電磁波耦合成地波。最後模擬與量測整個地波雷達系統，在10GHz及附近的頻段內具有地波增強功效，可用於地波雷達系統並實際應用。 ;A common high-frequency (HF) ground wave radar system is typically deployed along the shoreline (sand) for practical applications. However, the excited ground waves often suffer from energy loss and low transmission efficiency due to mode mismatch between the beach and seawater. Another common issue is the leakage of some energy into the sky, forming sky waves. After being reflected by the ionosphere, cause destructive interference at the receiving end. These challenges are referred to as ground wave issues. This paper will resolve the ground wave issues encountered by HF ground wave radar systems deployed along the shoreline and proposes a novel deployment method. The approach involves placing a phase gradient metasurface, composed of two substrate layers and metal strips, on the beach. The transmitting antenna directs incident waves vertically downward onto the metasurface, which facilitates the coupling of electromagnetic waves into ground waves and guides them along the seawater surface, thereby resolving the mode mismatch problem. Meanwhile, since most of the energy is coupled into ground waves, the proportion of sky waves is reduced, mitigating the destructive interference problem. Through simulations, this study determines the required reflection phase and corresponding geometric parameters for each metasurface unit. Using these unit designs with varying geometric parameters, a phase gradient metasurface is constructed. The metasurface introduces an additional wave vector component, enabling electromagnetic waves to couple into ground waves. Finally, simulations and measurements of the entire ground wave radar system demonstrate its effectiveness. Within the frequency range around 10GHz, the system exhibits ground wave enhancement, making it suitable for practical HF ground wave radar applications.
Appears in Collections:	[Graduate Institute of Electrical Engineering] Electronic Thesis & Dissertation

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