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1、Antenna Wireless 1886 HertZ 提出天線理論 1901 Marconi 把天線應用於生活上Antenna TheoryRadiation MechanismCreate radiation(a.) There must be a time-varying current or acceleration charge(b.) The wire must be curved、bent、discontinuous、 terminated or truncated Radiation MechanismField regions of an antennaRadiation P
2、atternDef：The radiation pattern is a graphical representation of radiation properties of the antenna as a function of space coordinates Classification1.Isotropic Pattern2.Directional Pattern3.Omnidirectional Patter Main lobe (major lobe) Side lobe Back lobe Half power beamwidth(FNBW) First null beam
3、width(FNBW) Radiation PatternCurrent distribution on TL 天線是TL的變形Current distribution on DipolesAntenna Parameter1. Radiation Power(輻射功率)2. Radiation Intensity(輻射強度)3. Radiation Resistance(輻射電阻)4. Directivity(方向性)DipoleDipoleDipole XZ plane E plane XY plane H planeRadiation PatternDipole radiation pa
4、tternHalf-wavelength DipoleD=1.64IsotropicD=1Dipole radiation patternVertical electric dipole above ground plane修正項Vertical electric dipole above ground planeVertical electric dipole above ground plane有適當的h提高天線效能將金屬板放置天 線後適當距離範例MonopoleFolded MonopolePIFA電感性，阻抗匹配用PIFAPIFA變形 全向性 線性極化PIFATwo-Element A
5、rrayAFEFAFEFTwo-Element ArrayEFAFTOTALCase (a)AFEFEFAFTOTALAFEFCase (b) 往相位落後方向發射及接收EFAFTOTALAFEFCase (c) 往相位落後方向發射及接收N-Element ArrayBroadside Array 每根天線具相同相位及電流Endside Array 往相位落後方向發射及接收 Endside Array 集中火力 Endside Array應用於雷達 Broadside Array 左右分散攻擊Patch Antenna Light weight、Small volume、Low cost Eas
6、y to integrate with MMIC Linear and circular polarizationAdvantagesDisadvantages Narrow bandwidth (high Q) Low Gain Low efficiencyFringing effect 模擬與量測會有差，起因為未考慮邊緣效應(fringing effect)Patch antenna Patch antenna Microstrip line feed 可利用此達到較佳的阻抗匹配Chip Antenna High dielectric constant Reduce the antenna sizeUWB ( Ultra Wideband ) 10m的短距離高速通訊 寬頻 高傳輸速率 低功率消耗(省電)UWB ( Ultra Wideband ) UWB Spectrum UWB vs IEEE802.11aUWB Antenna UWB Antenna 深度t及寬度w可用來達到最佳的阻抗匹配UWB Antenna 角度越大共振長度越短進入VSWA=2的頻率點就往高頻走UWB Antenna 半徑越大共振長度越長進入VSWA=2的頻率點就往低頻走
