电基本振子 参考文献 导航菜单

电磁学


天线坡印廷矢量






电基本振子辐射出的电场 (蓝色) 与磁场 (红色)


电基本振子(Electric Short Dipole)又称电流元, 指一段理想高频电流直导线,其长度l远小于波长λ并且其半径r远小于l,同时振子沿线的电流I处处等幅并且同相。这样的电流元可构成现实当中更复杂的天线, 因而电基本振子的辐射特性是研究更复杂天线辐射特性的基础。[1]


在球坐标当中,电基本振子在无限大自由空间中场强为[2]


Er=ZI0δℓ2π(1r2−ikr3)ei(ωt−kr)cos⁡(θ)displaystyle E_r=frac Z,I_0delta ell 2pi left(frac 1r^2-frac ikr^3right)e^i(omega t-k,r),cos(theta )
Eθ=iZI0δℓ4π(kr−ir2−1kr3)ei(ωt−kr)sin⁡(θ)displaystyle E_theta =ifrac Z,I_0delta ell 4pi left(frac kr-frac ir^2-frac 1kr^3right)e^i(omega t-k,r),sin(theta )
Hϕ=iI0δℓ4π(kr−ir2)ei(ωt−kr)sin⁡(θ)displaystyle H_phi =ifrac I_0delta ell 4pi left(frac kr-frac ir^2right)e^i(omega t-k,r),sin(theta )
Eϕ=Hr=Hθ=0,displaystyle E_phi =H_r=H_theta =0,

在近区场坡印廷矢量的均值Sav=12Re[E×H∗]displaystyle beginsmallmatrixmathbf S _av=frac 12Re[mathbf Etimes H^* ]endsmallmatrix
电基本振子的远区场表达式为:


Hϕ=jIl2λrsinθe−jkrdisplaystyle H_phi =jfrac Il2lambda rsintheta e^-jkr
Eθ=j60πIlλrsinθe−jkrdisplaystyle E_theta =jfrac 60pi Illambda rsintheta e^-jkr
Hr=Hθ=Er=Eϕ=0displaystyle H_r=H_theta =E_r=E_phi =0

电偶极子向自由空间辐射的总功率为


Pr=∮S⁡12Re[E×H∗]⋅ds=40π2I2(lλ)2 Wdisplaystyle P_r=oint _Sfrac 12Re[mathbf Etimes H^* ]cdot dmathbf s =40pi ^2I^2(frac llambda )^2 W


参考文献



  1. ^ [1] 宋峥. 天线与电波传播[M]. 2. 西安:西安电子科技大学出版社, 2011.


  2. ^ Silver, Samuel. Microwave Antenna Theory and Design. 1949: 92–94. 


Popular posts from this blog

名間水力發電廠 目录 沿革 設施 鄰近設施 註釋 外部連結 导航菜单23°50′10″N 120°42′41″E / 23.83611°N 120.71139°E / 23.83611; 120.7113923°50′10″N 120°42′41″E / 23.83611°N 120.71139°E / 23.83611; 120.71139計畫概要原始内容臺灣第一座BOT 模式開發的水力發電廠-名間水力電廠名間水力發電廠 水利署首件BOT案原始内容《小檔案》名間電廠 首座BOT水力發電廠原始内容名間電廠BOT - 經濟部水利署中區水資源局

Prove that NP is closed under karp reduction?Space(n) not closed under Karp reductions - what about NTime(n)?Class P is closed under rotation?Prove or disprove that $NL$ is closed under polynomial many-one reductions$mathbfNC_2$ is closed under log-space reductionOn Karp reductionwhen can I know if a class (complexity) is closed under reduction (cook/karp)Check if class $PSPACE$ is closed under polyonomially space reductionIs NPSPACE also closed under polynomial-time reduction and under log-space reduction?Prove PSPACE is closed under complement?Prove PSPACE is closed under union?

Is my guitar’s action too high? Announcing the arrival of Valued Associate #679: Cesar Manara Planned maintenance scheduled April 23, 2019 at 23:30 UTC (7:30pm US/Eastern)Strings too stiff on a recently purchased acoustic guitar | Cort AD880CEIs the action of my guitar really high?Μy little finger is too weak to play guitarWith guitar, how long should I give my fingers to strengthen / callous?When playing a fret the guitar sounds mutedPlaying (Barre) chords up the guitar neckI think my guitar strings are wound too tight and I can't play barre chordsF barre chord on an SG guitarHow to find to the right strings of a barre chord by feel?High action on higher fret on my steel acoustic guitar