隨著無線通訊技術的快速發展，無線通訊應用也越來越廣泛。為了兼容多個通訊系統的標準，對於雙頻或是多頻天線之需求也與日俱增。而傳統的多頻天線通常以分集或是植入槽孔的設計架構，容易有體積大、占空間的問題。
本研究以全平面式的結構與直接饋入的方式來設計天線，使其與基板較易整合，採用厚0.8mm的FR4基板，以相對介電係數(Relative Permittivity)為4.4，Dielectric Loss Tangent為0.02，來進行模擬並和實驗相驗證，設計兩種雙頻天線架構，其涵蓋應用範圍包括PCS/WCDMA1900、PHS、TDS-CDMA、WCDMA/IMT-2000、WLAN(802.11a)和WLAN(802.11-a/b/g/n)。
首先，回顧操作在1/4波長的平面單極天線，以此作為天線的初始結構，為了進一步縮小天線的尺寸，吾人深入比較平面倒L型天線與平面倒F型天線的特性，並且嘗試將兩個倒F型天線以背對背的方式，形成π型天線，且探討此π型天線的特性，並針對倒F型天線的窄頻缺點進行改善，使在低頻帶呈現寬頻效果。接著，進一步縮小尺寸，以設計出具實用價值的WLAN雙頻天線。
一些天線原型的實作量測結果與模擬皆非常相近，頻寬方面，分別可使低頻段(WCDMA/IMT-200)頻帶的頻寬由8.78%增加至21.11%；高頻段WLAN頻帶則可由原來的9.27%增加至17.15%。輻射場型的部分，實測結果顯示其H-plane(XZ-plane)在各個共振頻率點上均能有不錯的全方向(Omni-Directional)輻射場型特性。

With the rapid development of wireless communication technology, applications of various wireless communication are wide spread. For those communication systems to be compatible with multiple standards, dual and/or multi-frequency antennas are continuously increasing in demand. The traditional multi-frequency antennas usually require multi-path architecture and/or slit design, which tend likely to occupy a relatively large volume.
In this study, uni-planar structure with a coaxial feed is utilized to design the antennas so that it is easy to integrate with the PCB. The FR4 substrate with thickness 0.8mm is used, while the relative dielectric constant of 4.4 and loss tangent of 0.02 is used for simulation. Experiments are conducted to verify the design of the dual-band antenna structures that cover the frequency bands of PCS/WCDMA1900, PHS, TDS-CDMA, WCDMA/IMT-2000, WLAN (802.11a) and WLAN (802.11-a/b/g/n), etc.
    At first , the planar quarter-wavelength monopole antenna serves as an initial structure studied in this thesis. In order to reduce the antenna size, we compare the characteristics of the inverted L antenna and the inverted F antenna, and then examine the π-shape antenna, which can be viewed as resulted from two inverted F antenna with back to back, and to explore the characteristics of π-type antenna to overcome the narrowband shortcoming of the inverted F antenna. In addition to the bandwidth-broadening in the low-frequency band, we further introduce parasitic elements to achieve the a dual-band WLAN antenna design. Finally, try to reduce the size of the new design.
Several antenna prototypes are fabricated, while the measurement results show very good agreement with the simulation. As the bandwidth concerned the low-frequency (WCDMA/IMT-2000) bandwidth is increased from 8.78% to 21.11%, while the high-frequency WLAN bandwidth is increased from 9.27% to 17.15%. For the radiation patterns, experimental results show that the H-plane (XZ-plane) reveals a omni-directional characteristics at various frequencies.

目錄

中文摘要．．．．．．．．．．．．．．．．．．．．．．．．．．．I
英文摘要．．．．．．．．．．．．．．．．．．．．．．．．．．． III
第一章	序論．．．．．．．．．．．．．．．．．．．．．．．．． 1
1.1	研究背景．．．．．．．．．．．．．．．．．．．．．．． 1
1.2	研究動機．．．．．．．．．．．．．．．．．．．．．．． 2
1.3	論文架構．．．．．．．．．．．．．．．．．．．．．．． 5

第二章	天線原理．．．．．．．．．．．．．．．．．．．．．．． 6
2.1	單極天線．．．．．．．．．．．．．．．．．．．．．．． 6
2.2	倒L型天線 (Inverted L Antenna, ILA)．．．．．．．．．．． 8
2.2.1	單極天線與倒L型天線的特性比較．．．．．．．．．  9
2.3	倒F型天線 (Inverted F Antenna, IFA)．．．．．．．．．．．12
2.3.1	倒L型天線與倒F型天線的特性比較．．．．．．．． 13
2.4	針對PIFA天線窄頻的改良．．．．．．．．．．．．．．．18
2.4.1	π型天線．．．．．．．．．．．．．．．．．．．．22

第三章	天線設計與模擬．．．．．．．．．．．．．．．．．．．．27
3.1	簡介．．．．．．．．．．．．．．．．．．．．．．．．27
3.2	以π型結構設計的天線．．．．．．．．．．．．．．．．28
3.2.1	設計接地面寄生以達到高頻匹配的天線結構．．．．．34
3.2.2	引入二極體以達到高頻可調式的天線結構．．．．．．38
3.2.3	引入stubs以增加WLAN(5.8GHz)頻帶．．．．．．．41
3.2.4	實作與量測．．．．．．．．．．．．．．．．．．．46
3.3	設計縮小化的WLAN雙頻天線．．．．．．．．．．．．．55
3.3.1	引入stubs以增加WLAN(5.8GHz)頻帶．．．．．．．．62
3.3.2	參數調整以達成寬頻縮小化的目標．．．．．．．．．65
3.3.3	寬頻縮小化天線的實作與量測．．．．．．．．．．．68

第四章	結論．．．．．．．．．．．．．．．．．．．．．．．．．74





圖目錄

圖 2.1 (a) 單極天線 (b)單極天線電流分佈．．．．．．．．．．．．．6
圖 2.2 (a) 偶極天線及其輻射場形 (b)偶極天線有著串聯的電壓與對稱的平面 (c)單極天線在一接地面上．．．．．．．．．．．．．． 8
圖 2.3倒L型天線的示意圖．．．．．．．．．．．．．．．．．．． 9
圖 2.4單極天線被彎曲(Bend)成倒L型天線的示意圖．．．．．．． 10
圖 2.5 倒L型天線 (L=26mm,H=6.47mm)在頻率1.8GHz時的電流分佈
圖．．．．．．．．．．．．．．．．．．．．．．．．．． 10
圖 2.6 不同高度H與彎曲長度L的倒L型天線反射損耗模擬圖．．．．． 11
圖 2.7 不同高度H與彎曲長度L的倒L型天線的輸入阻抗圖．．．． 11
圖 2.8 倒F型天線的示意圖．．．．．．．．．．．．．．．．．． 13
圖 2.9 	倒F型天線圖(L=26mm, H=6.47mm, d=1.5mm)．．．．．．． 14
圖 2.10倒F型天線(L=26mm,H=6.47mm,d=1.5mm)的輸入阻抗圖．．． 15
圖 2.11倒L型天線圖與迴路型(Loop)天線圖的結構示意．．．．．．15-16
圖 2.12倒L型天線(L=26mm,H=6.47mm)與迴路型(Loop)天線於頻率1.68 GHz時的虛部阻抗圖．．．．．．．．．．．．．．．．．． 16
圖 2.13倒L型天線(L=26mm,H=6.47mm)與倒F型天線( L=26mm, H=6.47mm, d=1.5mm)的反射損耗值(Return Loss)圖．．．．．17
圖2.14 倒L型天線(L=26mm,H=6.47mm)的輸入阻抗圖．．．．．．．17
圖2.15 π型天線結構示意圖．．．．．．．．．．．．．．．．．．19
圖2.16 以重疊定理與奇偶模概念分析一對稱系統的示意圖．．．．．19
圖2.17 傳統型PIFA天線結構示意圖．．．．．．．．．．．．．．20
圖2.18 π型天線與傳統型PIFA天線的反射損耗值(Return Loss)圖．．21
圖2.19 π型天線與傳統型PIFA天線的輸入阻抗圖．．．．．．．．21-22
圖2.20 π型天線(針對寬度參數d作調整) ．．．．．．．．．．．．23
圖2.21 π型天線的反射損耗值(Return Loss)圖(寬度參數d為4.5mm、7.5mm及11.5mm) ．．．．．．．．．．．．．．．．．．24
圖2.22 π型天線在各頻率的電流分佈圖(寬度參數d為11.5mm) ．．24-25
圖2.23 π型天線的輸入阻抗圖(寬度參數d為4.5及11.5mm) ．．．25-26
圖3.1 中間迴圈長度以左右方式延伸的示意圖．．．．．．．．．．29
圖3.2 中間迴圈長度以向上方式延伸的示意圖．．．．．．．．．．29
圖3.3 中間迴圈長度以向下方式延伸的示意圖．．．．．．．．．．30
圖3.4 三種延伸方式的反射損耗值變化圖．．．．．．．．．．．．30
圖3.5三種延伸方式的輸入阻抗變化圖．．．．．．．．．．．．．31-33
圖3.6 中間迴圈長度以向下延伸的示意圖(引入寄生結構) ．．．．．35
圖3.7中間迴圈長度以向下延伸的反射損耗圖(引入寄生結構) ．．．35
圖3.8 引入寄生結構後的輸入阻抗變化圖．．．．．．．．．．．．36
圖3.9 加入寄生結構後的電流分佈圖．．．．．．．．．．．．．．37-38
圖3.10 為引入縫隙的示意圖 ．．．．．．．．．．．．．．．．．39
圖3.11 為引入二極體（逆偏）來調控天線的損耗值比較．．．．．．40
圖3.12 為引入二極體（逆偏）來調控天線的輸入阻抗圖比較．．．．40-41
圖3.13 為引入stubs後的天線結構示意圖．．．．．．．．．．．．．42
圖3.14 為引入stubs後的反射損耗圖．．．．．．．．．．．．．．43
圖3.15 為引入stubs後的輸入阻抗圖．．．．．．．．．．．．．．44
圖3.16 為引入stubs後的天線結構在各頻率的電流分佈圖．．．．．46
圖3.17 引入stubs的π型天線實體圖．．．．．．．．．．．．．．48
圖3.18 引入stubs的π型天線反射損耗圖．．．．．．．．．．．．49
圖3.19 引入stubs的π型天線於H-plane(X-Z平面)的輻射場型模擬與實        
       測結果(@1.9GHz) ．．．．．．．．．．．．．．．．．．49
圖3.20 引入stubs的π型天線於H-plane(X-Z平面)的輻射場型模擬與實  
       測結果(@1.95GHz) ．．．．．．．．．．．．．．．．．．50
圖3.21 引入stubs的π型天線於H-plane(X-Z平面)
       的輻射場型模擬與實測結果(@2.02GHz) ．．．．．．．．．50
圖3.22 引入stubs的π型天線於H-plane(X-Z平面)
       的輻射場型模擬與實測結果(@2.15GHz) ．．．．．．．．．51
圖3.23 引入stubs的π型天線於H-plane(X-Z平面)
       的輻射場型模擬與實測結果(@5.2GHz) ．．．．．．．．．．51
圖3.24 引入stubs的π型天線於H-plane(X-Z平面)
       的輻射場型模擬與實測結果(@5.8GHz) ．．．．．．．．．．52
圖3.25 引入stubs的π型天線於E-plane(Y-Z平面)
       的輻射場型模擬與實測結果(@1.9GHz) ．．．．．．．．．．52
圖3.26 引入stubs的π型天線於E-plane(Y-Z平面)
       的輻射場型模擬與實測結果(@1.95GHz) ．．．．．．．．．53
圖3.27 引入stubs的π型天線於E-plane(Y-Z平面)
       的輻射場型模擬與實測結果(@2.02GHz) ．．．．．．．．．53
圖3.28 引入stubs的π型天線於E-plane(Y-Z平面)
       的輻射場型模擬與實測結果(@2.15GHz) ．．．．．．．．．54
圖3.29 引入stubs的π型天線於E-plane(Y-Z平面)
      的輻射場型模擬與實測結果(@5.2GHz) ．．．．．．．．．．54
圖3.30引入stubs的π型天線於E-plane(Y-Z平面)
      的輻射場型模擬與實測結果(@5.8GHz) ．．．．．．．．．．55
圖3.31原天線架構的示意圖．．．．．．．．．．．．．．．．．．57
圖3.32 去除左側分支後的縮小化天線結構示意圖．．．．．．．．．57
圖3.33 去除右側分支後的縮小化天線結構示意圖．．．．．．．．．58
圖3.34 去除左側分支後的縮小化天線之反射損耗圖．．．．．．．．58
圖3.35 去除右側分支後的縮小化天線之反射損耗圖．．．．．．．．59
圖3.36 去除左側分支後的縮小化天線之輸入阻抗圖．．．．．．．59-60
圖3.37 去除右側分支後的縮小化天線之輸入阻抗圖．．．．．．．．60-61
圖3.38 右側長調整後的縮小化天線結構示意圖．．．．．．．．．．61
圖3.39 右側長度調整後的縮小化天線之反射損耗圖．．．．．．．．62
圖3.40為引入stubs後的縮小化天線示意圖．．．．．．．．．．．．63
圖3.41 為引入stubs後的縮小化天線反射損耗圖．．．．．．．．．64
圖3.42 為引入stubs後的縮小化天線輸入阻抗圖．．．．．．．．．65
圖3.43 調整接地面參數後的寬頻縮小化天線示意圖．．．．．．．．66
圖3.44 調整接地面參數後的寬頻縮小化天線之反射損耗圖．．．．．67
圖3.45 調整接地面參數後的寬頻縮小化天線之阻抗圖．．．．．．67-68
圖3.46 圖3.43的雙頻/寬頻縮小化WLAN天線實體圖．．．．．．．69
圖3.47 圖3.43的雙頻/寬頻縮小化WLAN天線反射損耗圖．．．．．70
圖3.48 圖3.43的雙頻/寬頻縮小化WLAN於H-plane(X-Z平面)
       的輻射場型模擬與實測結果(@2.4GHz) ．．．．．．．．．．70
圖3.49 圖3.43的雙頻/寬頻縮小化WLAN於天線H-plane(X-Z平面)
       的輻射場型模擬與實測結果(@5.2GHz) ．．．．．．．．．．71
圖3.50圖3.43的雙頻/寬頻縮小化WLAN天線於H-plane(X-Z平面)
       的輻射場型模擬與實測結果(@5.8GHz) ．．．．．．．．．．71
圖3.51 圖3.43的雙頻/寬頻縮小化WLAN天線於E-plane(Y-Z平面)
       的輻射場型模擬與實測結果(@2.4GHz) ．．．．．．．．．．72
圖3.52 圖3.43的雙頻/寬頻縮小化WLAN天線於E-plane(Y-Z平面)
       輻射場型模擬與實測結果(@5.2GHz) ．．．．．．．．．．．72
圖3.53 圖3.43的雙頻/寬頻縮小化WLAN天線於E-plane(Y-Z平面)
       的輻射場型模擬與實測結果(@5.8GHz) ．．．．．．．．．．73











表目錄

表 1.1　無線通訊系統各頻段規範範圍表．．．．．．．．．．．．． 4
表 2.1　虛部為零，實部與共振頻率隨高度H改變時的變化表．．．． 12
表 3.1　為引入stubs後的示意圖參數長度．．．．．．．．．．．． 42
表 3.2  H-plane(X-Z平面)輻射場形在各頻率點的增益．．．．．．． 47
表 3.3  E-plane(Y-Z平面)輻射場形在各頻率點的增益．．．．．．． 48
表 3.4  為引入stubs後的天線結構之參數長度(縮小天線尺寸)．．．． 63
表 3.5  調整接地面參數後的寬頻縮小化天線之參數長度．．． ．． 66
表 3.6  彎折型迴路天線(Lm=5mm)各參數長度．．．．．．．．．． 60

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