開口式共振腔之時域與頻域分析

Abstract

本文討論的低Q值的開口式共振腔常應用於磁旋振盪管(gyromonotron oscillator)及磁波調速管(gyroklystron)。 可以知道開口式共振腔不同於封閉式共振腔乃是因為缺乏一個明顯的邊界，為了對其基本性質深入瞭解，因此針對兩個開口式共振腔特性詳加闡述: 共振頻率 ƒ0 、品質因素 Q 。 內文將以兩種不同模型： (1)時域法 (2)頻域法，在第一種模型中會將主腔體長度改變、角度改變去討論Q值與頻率的影響，再討論不同場型的分佈影響；第二種模型將以最大場強法、總場能法與反射法去討論不同方法的異同，藉由模態疊加效應分清方法的差異，再跟第一種模型做理論推導與數值模擬，並針對其中的不同，加以探討與比較，然而可以經由理論推導，去做出總場能法與反射法的近似，以達到理論模理與實驗的結合。

For open-end cavities generally used in gyrotrons, the lack of a well-defined geometrical boundary gives rise to distinctive feature as well as physics that are basically different from the closed cavity. We are concerning the consistency that time and frequency domain interpretations of the resonant frequency and quality factor . In the time domain, we change cavity size to discuss quality factor and resonant frequency. In the spectral domain, we can use different methods to get quality factor. The methods are maximum-field, the field energy, reflection spectrum. The field energy spectrum can be constructed from the power of the reflected waves, and compared time domain model to analyze some difference.