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http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/71063
標題: | 高效能波導透射天線設計工具的開發及提高其掃描角度能力 Development of Efficient Waveguide Transmitarray Antenna Design Tool and Improvisation of Their Scan Angle Capability |
作者: | Siddhartha Panigrahi 潘西和 |
指導教授: | 周錫增(Hsi-Tseng Chou) |
關鍵字: | 高增益天線,發射陣列,透鏡天線,輻射方向圖,發射陣列設計工具, High gain antenna,transmitarrays,lens antenna,radiation pattern,transmitarray design tool, |
出版年 : | 2018 |
學位: | 碩士 |
摘要: | 本論文基於波導式發射陣列天線(Waveguide Transmitarray Antenna)的架構下,設計一套便捷且高效率的電磁模擬工具。波導式發射陣列天線由於其低成本和高天線增益等特性,因此被廣泛使用於各種長距離訊號傳輸中,相關應用包含衛星電視、衛星遙測和太陽能集中系統等。而為滿足高天線增益(>20dBi) 和高指向性的需求,陣列天線中的單元個數往往極為龐大,進而造成一般商用模擬軟體在電磁模擬上的困難。此外,在天線場形合成的應用中,需對於天線場形進行反複檢查,而這也將導致商用模擬軟體的模擬效率的低落。再者,若有天線結構上的微小調整,商用模擬軟體都必須重新執行所有模擬步驟。因此,為克服商用軟體的上述幾項不足,不同於其全波(Full-wave) 分析模式,本論文將建構一套簡易的數學模型和相關公式以評估天線的電磁特性。
為完成數學公式的計算,本論文首先針對通過天線單元或波導的入射波,進行電磁場的分析和相關模型的建構,然後計算由饋電端到波導的總功率。最後,藉由計算各單元的表面電流密度加以推導其輻射場形的泛用方程式。天線結構的特徵將透過考慮兩個表面和波導的折射率來描述。對於單一波束的情況,僅需對一個表面進行建模也因此只需要一個波源。而對於多個波束的情形,天線結構的兩個表面和兩個波源均需使用,而此一情況已被多位學者加以研究,並發現整體的掃描角度相當小。上述現象促使我們將每個波導的折射率視為第三個變數,並可以增加一個額外的波源於聚焦的弧線上。相較於其他波導式陣列天線,此種方法能有效提高天線的角度掃描能力。 論文的最後,天線的輻射方程和相關的結構參數被一一應用於電磁模擬軟體的建構,以提供波導式發射陣列天線在電磁分析和場形預測上的便利性。 This project aims to design a simple and efficient simulation tool for waveguide transmitarray antenna. They are a low cost, high gain solution for different long range applications like satellite TV applications, earth remote sensing, solar energy concentrator etc. They provide a very high gain (>20dBi) and a highly directive pattern. As array technique is used to achieve the gain of this magnitude, the number of cell elements for such antennas are very large. To simulate such structures, with large number of elements, using commercial software can be a tedious task as they are time consuming. Also in applications like pattern synthesis where we need to check the antenna pattern frequently as the solutions are often not convex, the commercial simulation software reduces the overall work efficiency. Moreover, for every minor change, the structure should be rebuilt every time. These problems can be overcome by establishing a simplified mathematic model and formulation to estimate the structure, instead of full wave simulation of a complete structure. To calculate the formulation, a mathematical model was first developed to calculate the component of the incident field that is propagated through the unit cell elements or waveguides in this case. Then the total power transferred from the feed to the waveguide was calculated. Finally, a generic radiation equation was derived by calculating the surface current densities for individual cell elements and also for the array. The structure of the array was determined by considering two surfaces of the array and the refractive index of the waveguides as variables. For a single beam case, only one surface was modeled and hence only one source is required. For multi-beam case, two surfaces of the array were modeled using two sources. This case has already been studied by various authors and it has been found that, the scan angle for such system is small. Hence a novel approach of considering refractive index of each waveguide as a third variable has been used. This allows us to put another source in the focal arc on the axis of antenna. This approach had a better scan angle capability than other waveguide array antennas. The radiation equations and the structural parameters are then used to build the waveguide transmitarray simulation tool for different configurations for faster pattern prediction. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/71063 |
DOI: | 10.6342/NTU201802200 |
全文授權: | 有償授權 |
顯示於系所單位: | 電信工程學研究所 |
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