臺灣博碩士論文加值系統

本文提出運用在K及Ka雙頻帶之正交模態轉換器，其共用端開口面為圓形，發射端與接收端為矩形。此元件係天線饋電系統的一部分，可合併或分離正交極化訊號，並且為了防止儀器之間的干擾，在接收端與發送端之間並不能有訊號通過，故相當要求接收端與發射端之間的隔離度。首先提出利用隔板式架構做設計，此結構包含了緩變式阻抗轉換器，在側端與過渡區分別放置不同形狀的隔板，可增加正交極化的效果，但這種結構會增加加工的複雜度，並且提高成本。為了解決這樣的問題，因此提出一個即使不使用隔板及鉚釘，也可以使正交極化分離。該結構接收端(Tx)為漸變式架構，發射端(Rx)為步階式架構，利用電磁模擬軟體HFSS最佳化取得最佳尺寸，並用FEKO再做第二次模擬驗證，最後探討實作與模擬兩者結果不相符的原因。

In this thesis, we have proposed a miniature broadband orthomode transducer (OMT) used in K and Ka band. In order to prevent interference between between receiver port and transmitter port,we use the septum structure toattain enough isolation (not less than 30 dB). This structure includes a tapered impedance transformer, and septums with different shapes are placed in the receiver port and transition region. Such arrangement can effectively decrease cross-polarization between two orthogonal polarizations, but increases the manufacture complexity and cost. Therefore, we proposed a novel OMT structure which neither septums nor pins are used. In this structure, the transmitter port is tapered directly into the common port, and the receiver port is matched to the common port using the stepped impedance transformer. We use HFSS and FEKO to obtain the optimal structure dimensions. Finally, the measurement and simulation results are discussed.

摘要 i
Abstract ii
誌謝 iii
目錄 iv
圖目錄 vi
表目錄 ix
第一章 緒論 1
1-1 研究背景與動機 1
1-2 文獻探討 2
1-3 論文大綱 3
第二章 波導管結構 4
2-1 簡介 4
2-2 矩形波導管 5
2-3 圓形波導管 9
2-4 方形波導管 14
第三章 號角天線 16
3-1 簡介 16
3-2 矩形號角天線 17
3-2-1 E平面扇形號角天線 17
3-2-2 H平面扇形號角天線 19
3-2-3 角錐形號角天線 21
3-3 圓錐形號角天線 22
3-4 波紋狀號角天線 24
3-5 標準角錐形與含有波浪狀結構之模擬結果比較 25
3-6 結論 29
第四章 正交模態轉換器 30
4-1 簡介 30
4-2 極化器 31
4-3 彎曲波導管 32
4-4 正交模態轉換器分析 33
4-5 隔板式正交模態轉換器 34
4-5-1 規格選定 34
4-5-2 理論設計 34
4-5-3 模擬結果 35
4-7 改善型正交模態轉換器 42
第五章 結論 57
參考文獻 58
附錄A 60
附錄B 64
B-1 波導管轉接器 64
B-2 轉接頭實際成品與模擬結果 67

圖目錄
圖1-1VSAT架構圖.............................2
圖2-1標準矩形波導管........................5
圖2-2矩形波導管的模態位階趨勢圖............................7
圖2-3矩形波導管各模態電場與磁場分布圖................8
圖2-4標準圓形波導管........................9
圖2-5圓形波導管的模態位階趨勢圖..........................12
圖2-6圓形波導管各模態電場與磁場分布圖..............13
圖2-7方形波導管的模態位階趨勢圖..........................14
圖2-8方形波導管各模態電場與磁場分布圖..............15
圖3-1常見的典型號角天線結構..................................16
圖3-2E平面扇形號角天線半功率波束寬度與角度之對比關係圖.......18
圖3-3E平面扇形號角天線指向性與開口長度之關係圖...............18
圖3-4E平面扇形號角天線之(3-2)式關係圖...............19
圖3-5H平面扇形號角天線半功率波束寬度與角度之對比關係圖......20
圖3-6H平面扇形號角天線指向性與開口長度之關係圖............20
圖3-7H平面扇形號角天線之(3-5)式關係圖..............21
圖3-8圓錐形號角天線指向性與開口長度之關係圖..................23
圖3-9圓錐形號角天線之最大相位誤差與指向性之修正係數的關係圖........23
圖3-10波紋狀號角天線....................24
圖3-11角錐形號角天線....................26
圖3-12角錐形號角天線3D場形圖.............................26
圖3-13角錐形號角天線2D場形圖.............................27
圖3-14波浪狀角錐形號角天線....................................27
圖3-15波浪狀角錐形號角天線3D場形圖.................28
圖3-16波浪狀角錐形號角天線2D場形圖.................28
圖3-17角錐形號角天線2D場形比較結果圖.............29
圖4-1標準OMT工作原理的方塊圖...........................30
圖4-2標準方形極化器......................31
圖4-3彎折波導管..............................33
圖4-4步階式阻抗匹配......................35
圖4-5緩變式阻抗匹配示意圖................................35
圖4-6圓形轉矩形波導管..................36
圖4-7圓形波導管在各階模時下的截止頻率點分布趨勢...................36
圖4-8圓形轉矩形波導管電場分布圖..........................37
圖4-9圓形轉矩形波導管之插入損失與反射損失.....................37
圖4-10隔板式OMT..........................39
圖4-11隔板式OMT在RX端響應圖..........................39
圖4-12隔板式OMT在18~20.5GHZ激發RX端方向之電場圖.........40
圖4-13隔板式OMT在18~20.5GHZ激發TX端方向之電場圖.........40
圖4-14隔板式OMT在TX端響應圖...........................41
圖4-15隔板式OMT在28~30.5GHZ激發TX端方向之電場圖..........41
圖4-16隔板式OMT在28~30.5GHZ激發RX端方向之電場圖.........42
圖4-17改善型圓形轉矩形波導管................................43
圖4-18改善型圓形轉矩形波導管響應圖....................43
圖4-19改善型OMT..........................44
圖4-20改善型OMT在RX端響應圖..........................44
圖4-21改善型OMT在TX端響應圖..........................45
圖4-22實際加工含倒角之結構...........................46
圖4-23對切結構成品圖....................47
圖4-24一體成型結構成品圖............47
圖4-25TX端量測與模擬結果之反射損失S11.............48
圖4-26TX端量測與模擬結果之反射損失S22.............48
圖4-27TX端量測與模擬結果之插入損失S12.............49
圖4-28TX端量測與模擬結果之插入損失S21.............49
圖4-29TX端量測與模擬結果之隔離度S23.................50
圖4-30TX量測與模擬結果之隔離度S32.....................50
圖4-31RX量測與模擬結果之反射損失S11.................51
圖4-32RX量測與模擬結果之反射損失S33.................51
圖4-33RX量測與模擬結果之插入損失S13.................52
圖4-34RX量測與模擬結果之插入損失S31.................52
圖4-35RX端量測與模擬結果之隔離度S23.................53
圖4-36RX端量測與模擬結果之隔離度S32.................53
圖4-37考慮多模狀況下之模擬結果............................54
圖4-38對切結構與一體成型結構之RX端SYX...........55
圖4-39對切結構與一體成型結構之RX端SXY...........55
圖4-40對切結構與一體成型結構之TX端SYX...........56
圖4-41對切結構與一體成型結構之TX端SXY...........56
圖B-1量測K頻帶反射損失與插入損失的接法........65
圖B-2量測KA頻帶反射損失與插入損失的接法..............65
圖B-3實際量測.................................65
圖B-4各類波導管轉接器.................68
圖B-5WR42圓形轉矩形波導管..................................69
圖B-6WR42圓形轉矩形波導管響應圖......................69

表目錄
表2-1 圓形波導管在TE波的p 'nm值............................11
表2-2 圓形波導管在TM波的p nm值...........................11
表B-1 轉接頭類型規格.....................66

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