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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 Theory,Radiation Mechanism,Create radiation,(a.)There must be a time-varying current or acceleration charge,(b.)The wire must be curved、bent、discontinuous、terminated or truncated,Radiation Mechanism,Field regions of an antenna,Radiati
2、on Pattern,Def：The radiation pattern is a graphical representation of radiation properties of the antenna as a function of space coordinates,Classification,1.Isotropic Pattern,2.Directional Pattern,3.Omnidirectional Patter,Main lobe(major lobe)Side lobe Back lobe Half power beamwidth(FNBW)First null
3、 beamwidth(FNBW),Radiation Pattern,Current distribution on TL,天線是TL的變形,Current distribution on Dipoles,Antenna Parameter,1.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),Dipole,Dipole,Dipole,XZ plane E plane XY plane H plane,Radiation Pattern,Dipole ra
4、diation pattern,Half-wavelength DipoleD=1.64,IsotropicD=1,Dipole radiation pattern,Vertical electric dipole above ground plane,修正項,Vertical electric dipole above ground plane,Vertical electric dipole above ground plane,將金屬板放置天線後適當距離,範例,Monopole,Folded Monopole,PIFA,電感性，阻抗匹配用,PIFA,PIFA變形,全向性,線性極化,PIF
5、A,Two-Element Array,AF,EF,AF,EF,Two-Element Array,EF,AF,TOTAL,Case(a),AF,EF,EF,AF,TOTAL,AF,EF,Case(b),往相位落後方向發射及接收,EF,AF,TOTAL,AF,EF,Case(c),往相位落後方向發射及接收,N-Element Array,Broadside 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
6、,Light weight、Small volume、Low costEasy to integrate with MMICLinear and circular polarization,Advantages,Disadvantages,Narrow bandwidth(high Q)Low Gain Low efficiency,Fringing 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 size,UWB(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 IEEE802.11a,UWB 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,
