簡單天線的電磁輻射

Electromagnetic Radiation from Some Simple Antennas

10.30173/JG.201206.0007

柳銘哲(Ming-Tse Liu)

電磁輻射 ； 赫茲電偶極子 ； 磁偶極子 ； 對稱振子 ； 均勻線性陣列 ； electromagnetic radiation ； Hertzian electric dipole ； magnetic dipole ； dual dipole ； uniform linear array

加馬

43期（2012 / 06 / 01）

51 - 61

繁體中文

電磁輻射是帶電粒子放射或吸收能量的一種型式，當它在自由空間傳播時顯現波的性質。電磁輻射裡有電場和磁場的成份，它們的相位隨著空間和時間振盪且互相垂直，並和波及能量傳播的方向垂直。電磁輻射是更一般的電磁場的一種特別型式，而電磁場是加速電荷產生的。我們在這裡討論一個被給定的電荷和電流分布如何產生和輻射電磁波。典型上，電荷分布被侷限在某個空間區域（例如，電流在一個天線上），這電流源產生電磁場，而這電磁場可以傳播到離源頭位置很遠的距離。我們計算了赫芝電偶極子、磁偶極子、對稱振子、和n元均勻線性陣列的輻射場，我們也畫了這些場的總場方向圖（total field pattern），它是元方向圖和陣方向圖的積。

Electromagnetic radiation (EM radiation or EMR) is a form of energy emitted and absorbed by charged particles, which exhibits wave-like behavior as it travels through space. EMR has both electric and magnetic field components, and which oscillate in phase perpendicular to each other and perpendicular to the direction of energy and wave propagation. Electromagnetic radiation is a particular form of the more general electromagnetic field (EM field), which is produced by accelerating charges. Here we discuss how a given distribution of currents and charges can generate and radiate electromagnetic waves. Typically, the current distribution is localized in some region of space (for example, currents on a wire antenna.) The current source generates electromagnetic fields, which can propagate to far distances from the source location. We calculate the EM far-fields which are caused by the Hertzian dipole, magnetic dipole, dual dipole, and n elements uniform linear array. We also plot total fieldpatterns of those previous source configuration.