臺灣博碩士論文加值系統

本論文研究軸心主要是圓極化槽孔天線設計，論文首先介紹圓極化產生的方式，並且分別利用公式與模擬軟體進行相關的參數分析，並提出一種新的圓極化環型槽孔天線的饋入方法。天線是由環型槽孔以及V型的耦合線所組成，並在耦合線的其中一端放置電阻負載，因此天線可視為一個雙饋入網路。環型槽孔天線必須滿足特定的條件才能產生圓極化輻射，而藉由參數分析，我們提出了幾種可改變S參數的方法，並利用這些方法成功的設計出不同槽孔寬度的天線。以窄槽孔天線為例，圓極化可以很容易的藉由在耦合線末端放置電阻負載來產生。而對寬槽孔天線而言則可藉由調整V型耦合線的夾角來獲得良好的圓極化特性。實驗與模擬結果同樣具有良好的一致性。
第二部份為頻率重置圓極化槽孔天線設計，藉由L型耦合線與電抗性負載激發圓極化。首先在槽孔內部對稱放置四個晶片電容，並藉由改變電容值使圓環型槽孔天線的圓極化頻率產生改變，同時於微帶線末端放置另一個晶片電容以等效殘枝的電子特性，使其在各個頻帶下均可達成理想圓極化操作。實驗結果顯示圓極化操作頻率可以由1.5 GHz變化至3.5 GHz。最後利用變容二極體取代晶片電容，藉由外部偏壓控制變容二極體的電容值，設計出具有可調頻率之圓極化槽孔天線，可調頻率範圍約為34.5 %。

The purpose of the thesis is to investigate the designs of circularly-polarized (CP) slot antenna. To begin with, the method of generating CP is demonstrated, and the related parameters are analyzed by mathematical formulas and commercial simulation software, respectively. Then, a new feeding method to CP ring slot antennas is described. The antenna structure is composed of an annular-ring slot and a V-shaped coupling line. A resistive loading is placed at one end of the coupling line whereby the antenna is considered as a two-port network. It is found that the S parameters of the two-port network need to satisfy a specific condition for generating CP radiation from the annular-slot antenna. Several ways of varying the S parameters are investigated, and based on the obtained results, a number of the CP slot antenna with various ring width are successfully designed. For a thin slot antenna, the CP generation can be easily achieved with the coupling line loaded the resistor, and the resistance value is not sensitive to the axial ratio. As for a wide slot antenna, good CP performance can be obtained through adjusting the included angle of the V-shaped coupling line. Experimental results for these designs are also given, and they agree well with simulated results. Finally, a frequency reconfigurable slot antenna with CP is proposed. The antenna operates at one full-wavelength resonant mode and it is excited by an L-shaped coupling line with a reactive loading. It is found that the operating frequency of the slot antenna can be tuned by varying the capacitance values of four capacitors which are symmetrically placed along the circumference of the ring slot. Moreover, for each operating frequency in the tunable range, good CP performance can be obtained as long as the reactance of the loading is properly adjusted. Both measured and simulated results indicate the CP operating frequency of the proposed design can be tuned between 1.5 and 3.5 GHz. A prototype integrating with two varactor diodes is also implemented so that the CP operating frequency can be switched by controlling dc biases. Details of the antenna designs and measured results are presented and discussed.

目 錄
摘　要 i
Abstract ii
致 謝 iii
目 錄 iv
圖目錄 vi
表目錄 ix
第一章 序論 1
1.1 概述……………………………………………………………………1
1.2 文獻探討………………………………………………………………3
1.3 內容提要………………………………………………………………7
第二章 圓極化電磁波探討 9
2.1 概述……………………………………………………………………9
2.2 圓極化的定義………………………………………………………..10
2.3 計算與模擬結果……………………………………………………..12
第三章 槽孔天線之簡單圓極化設計 16
3.1 概述…………………………………………………………………..16
3.2 具開路殘枝的環型槽孔天線之結構分析…………………………..18
3.2.1 實驗結果...........................20
3.3 具負載電阻的圓極化槽孔天線之結構分析………………………..23
3.3.1 V型耦合線寬度的分析與探討…...……………………...…..…25
3.3.2 負載電阻值的分析與探討……………………………………...30
3.3.3 V型耦合線的夾角分析與探討…………………………………37
3.4 不同寬度的槽孔圓極化天線設計…………………………………..39
第四章 具有可調頻率之圓極化槽孔天線設計 48
4.1 概述…………………………………………………………………..48
4.2 頻率重置之圓極化槽孔天線設計概念……………………………..50
4.3 具有電容負載的圓極化槽孔天線…………………………………..55
4.3.1 實驗結果………………………………………………………...57
4.4 具有可調頻率之圓極化槽孔天線設計……………………………..63
4.4.1 實驗結果………………………………………………………...65
第五章 結論 72
參考文獻 74
附錄 79

圖目錄
圖2.1 橢圓極化示意圖 11
圖2.2 傳統雙饋入微帶天線幾何結構圖 13
圖2.3 不同的相位差所對應之軸比圖 14
圖2.4 不同的振幅比值所對應之軸比圖 15
圖3.1 開路殘枝環型槽孔天線結構圖 19
圖3.2 參考天線之實測與模擬結果 21
圖3.3 參考天線於2.43 GHz所量測的輻射場型 22
圖3.4 負載電阻圓極化槽孔天線結構圖 24
圖3.5 改變W之模擬結果 27
圖3.6 不同寬度W下之計算結果 28
圖3.7 不同饋入線寬度之模擬與計算之軸比變化圖 29
圖3.8 改變RL之模擬結果 32
圖3.9 不同電阻值RL之計算結果 33
圖3.10 模擬與計算之軸比變化圖 34
圖3.11 模擬與量測之增益變化圖 35
圖3.12 傳遞損失圖 36
圖3.13 改變θ對軸比變化之影響圖 38
圖3.14 不同設計之量測結果 41
圖3.15 天線C,D,E,F之量測結果 42
圖3.16 天線B於2.42 GHz所量測的輻射場型 43
圖3.17 天線C於2.67 GHz所量測的輻射場型 44
圖3.18 天線D於2.79 GHz所量測的輻射場型 45
圖3.19 天線E於2.92 GHz所量測的輻射場型 46
圖3.20 天線F於2.98 GHz所量測的輻射場型 47
圖4.1 開路殘枝圓極化槽孔天線結構圖 52
圖4.2 使用電容取代之圓極化槽孔天線結構圖 53
圖4.3 參考天線之模擬結果 54
圖4.4 具有電容負載的圓極化槽孔天線結構圖 56
圖4.5 不同晶片電容值的實驗結果 58
圖4.6 不同C2量測之軸比變化圖 59
圖4.7 天線操作於3.51 GHz所量測的遠場輻射場型 60
圖4.8 天線操作於1.51 GHz所量測的遠場輻射場型 61
圖4.9 天線操作在不同頻率下的增益變化圖 62
圖4.10 具有可調頻率之圓極化槽孔天線幾何結構圖 64
圖4.11 不同偏壓的實測與模擬結果 66
圖4.12 天線操作於2.34 GHz所量測的遠場輻射場型 67
圖4.13 天線操作於1.99 GHz所量測的遠場輻射場型 68
圖4.14 天線操作於1.8 GHz所量測的遠場輻射場型 69
圖4.15 天線操作於1.65 GHz所量測的遠場輻射場型 70
圖4.16 天線操作在不同頻率下的增益變化圖 71

表目錄
表3.1 在最佳圓極化的頻率下不同耦合線寬度對天線的影響 25
表3.2 不同負載電阻值對天線的影響 30
表3.3 不同槽孔寬度的影響及其它相關天線尺寸 40

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