| 摘要: | 本篇論文主要探討展開網狀反射面天線結合超表面運用於衛星天線系統上，希望設計出能夠在工作頻寬內擁有穩定高增益與高指向性來達成太空任務。研究著重於三個部分，包含饋入天線系統、展開網狀反射面天線系統與改進展開網狀反射面天線增益的超表面。
饋入天線系統設計主要以鋁製作完成，結構有兩個部份，一為號角天線，二為正交模態轉換器。在中心頻率9.5GHz時，垂直極化端口與水平極化端口量測的增益分別為9.54dBi與9.58dBi，極化隔離度均達到30dB以上。
對於展開網狀反射面天線系統而言，本篇論文設計了一個焦距為1.5米、直徑為3.8米、F/D為0.39的反射面天線。本篇論文分析了理想拋物反射面天線與實際工程製造考量的差異，針對拋物反射面的傘骨數量、環形平台面積大小進行了不同結構的模擬比對，包含模擬傘骨數量24隻、30隻、36隻與環形平台大小1.1米和1.4米。希望衛星天線系統在可用的酬載體積與重量限制下，保有機械結構穩定度與高增益、低旁辦波束的射頻性能。本篇論文中所設計的理想拋物反射面天線在中心頻率9.5GHz時，垂直極化端口激發的增益為49.52 dBi，水平極化端口激發的增益為 49.55dBi。在各項機械穩定度的評估後，選擇36隻傘骨與1.1米環形平台來平衡機械結構與電性的取捨，但這也導致增益的下降。
本篇論文發現在展開網狀反射面天線系統中，環形平台的大小對增益的影響最為明顯。所以本篇論文提出了一個超表面天線取代環形平台，藉由不同尺寸的超表面天線單元產生不同所需的反射補償相位，所設計的超表面天線單元反射補償相位涵蓋0~360度，並擁有很好的反射補償相位梯度斜率。為驗證所設計的超表面天線單元，本篇論文設計了一個焦距為190mm，直徑為480mm的超表面天線。在中心頻率9.5GHz時，垂直極化端口激發的增益為29.95 dBi，水平極化端口激發的增益為30.05dBi，模擬與量測兩者的增益近乎貼合。相比之下，當超表面天線替換成只有環形平台的平面結構時，增益僅為11.45dBi。同時，本篇論文也模擬了相同焦距直徑比的理想拋物反射面天線，儘管超表面天線的增益仍比理想拋物反射面天線低1.4dBi，但超表面天線已經大幅彌補了因環形平台所損失的增益。
最後，本篇論文將所設計的超表面天線單元與包含36隻傘骨和1.1米環形平台的展開網狀反射面天線結合，模擬結果顯示，所設計的超表面天線在改善展開網狀反射面天線增益有很大的效果，改善了因環形平台對展開網狀反射面天線所帶來的影響。
;This paper primarily explores the deployable mesh reflector antennas with metasurfaces in satellite antenna systems. The objective is to devise a system that can maintain high gain and high directivity throughout the operating bandwidth, thereby enhancing its suitability for space missions. The research is centered around three key components: the feed antenna system, the deployable mesh reflector antenna system, and the metasurfaces to enhance the gain of the deployable mesh reflector antenna.
The feed antenna system design is mainly made of aluminum. This structure comprises two main components: a horn antenna and an orthomode transducer. At the central frequency of 9.5 GHz, the measured gains for the vertical polarization port and horizontal polarization port are 9.54 dBi and 9.58 dBi, respectively. Additionally, the polarization isolation exceeds 30 dBi.
In the context of the deployable mesh reflector antenna system, this paper presents the design of a reflector antenna featuring a focal length of 1.5 meters and a diameter of 3.8 meters, the F/D ratio is 0.39. This paper examines the disparities between the ideal parabolic reflector antenna and practical engineering manufacturing constraints. It conducts a simulation-based comparative analysis of various configurations, varying the number of parabolic reflector ribs and the dimensions of the circular platform. The simulations include cases with 24, 30, and 36 ribs, along with circular platform sizes of 1.1 meters and 1.4 meters. The aim is to ensure that the satellite antenna system maintains mechanical and structural stability while delivering high-gain, low side lobe level performance within the given payload volume and weight limitations.The ideal parabolic reflector antenna designed in this paper is operated at a center frequency of 9.5 GHz, the gain for the vertical polarization port is 49.52 dBi and the gain for the horizontal polarization port is 49.55 dBi. After various mechanical stability evaluations, 36 ribs and a 1.1-meter circular platform were selected to balance the trade-off between mechanical structure and electrical properties, but this also resulted in a decrease in gain.
This paper found that the size of the circular platform has the most obvious impact on the gain in the deployable mesh reflector antenna system. Therefore, this paper proposes a metasurfaces antenna to replace the circular platform. Through metasurfaces of different sizes, The antenna unit generates different required reflection compensation phases. The designed metasurfaces antenna unit reflection compensation phase covers 0~360 degrees and has a good reflection compensation phase gradient slope. In order to verify the designed metasurfaces antenna unit, this paper designed a metasurfaces antenna with a focal length of 190mm and a diameter of 480mm. At the center frequency of 9.5GHz, the gain excited by the vertical polarization port is 29.95dBi, and the gain excited by the horizontal polarization port is 30.05dBi. The gains of simulation and measurement are almost consistent. In comparison, when the metasurfaces antenna was replaced with a planar structure with only a circular platform, the gain was only 11.45dBi. At the same time, this paper also simulates an ideal parabolic reflector antenna with the same focal length to diameter ratio. Although the gain of the metasurfaces antenna is still 1.4dBi lower than that of the ideal parabolic reflector antenna, the metasurfaces antenna has greatly made up for the loss caused by the circular platform.
Finally, this paper combines the designed metasurfaces antenna unit with a deployable mesh reflector antenna containing 36 ribs and a 1.1-meter circular platform. The simulation results show that the designed metasurfaces antenna improves the performance of the deployable mesh reflector antenna. The gain has a great effect and improves the impact of the circular platform on the deployable mesh reflector antenna. |
