迴轉磁性平面傳輸線洩漏模及複數模的全波分析

Abstract

在本論文中, 迴轉磁性平面傳輸線的格林函數被有系統地建立起來, 最後 配合 Galerkin's method以進行全波數值分析。首先討論從不具反方向性 部分封閉迴旋磁體槽線高階洩漏波到完全封閉迴旋磁體槽線高階複數模的 演進過程，經由一系列的數值實驗及分析, 可歸納出封閉槽線複數模的形 成乃是金屬蓋加諸於洩漏模間的偶合效應所引起的; 此項結論也給予了本 實驗室先前發表有耦合理論模型中假設模的物理意義。相對於前述不具反 方向性封閉結構的高階複數模，基本複數模被發現存在於側邊開放且垂直 磁化的耦合微帶線上，不同於均方介質的耦合微帶線，此迴旋磁體偶合微 帶線在對稱情形下, 準偶模及準奇模間存在著模耦合現象假如兩條金屬導 線的寬度差異很大, 一對主複數模將存在於大部分的頻率範圍,其間唯一 的通帶則可由外加磁化磁場控制。另外, 由於金屬厚度及上、下陶鐵磁體 基板無法完全地契合, 不可避免地有一微小氣隙存在於迴轉磁性條狀線的 中央區域; 理論分析顯示, 同不均勻的均方介質條狀線一樣, 主模將會洩 漏電磁能量且存在另一不會洩漏的類平行板主模, 然而使用陶鐵磁體的好 處是, 在適當的工作頻率及磁化磁場下, 能量洩漏是可以被抑制的。最後 因陶鐵磁體的電磁特性可由外加的直流偏壓(磁化)線路所控制,一種工作 於迴旋磁體微帶線第一高階洩漏模的磁性掃瞄式漏波天線被提出並予以分 析, 只要變化約6.5%的偏壓磁場, 主輻射束角度可從水平揚至約九十度, 且隨偏壓磁場大小線性地改變。 The dyadic Green's imprdance functions of gyromagnetic planar transmission lines are systemmatically established models. Full- wave numerical analyses are performed by appling the Galerkin's method. After performing a series of numerical experiment, we conclude that the formation of the complex modes on the shielded gyromagnetic slotline is the result of coupling effects, caused by the presences of covers, among the leaky modes. A pair of dominant complex modes is formed on the reciprocal gyromagnetic coupled microstrips. By properly tunning the strip widths, a bandpass spectrum can be formed for such a guided wave structure and the passband was shown to be magnetically tunable. The same inhomogeneous stripline, the conventional dominant stripline mode becomes leaky and a parallel-plate-like dominant bound mode coexists with it. However, the dominant-mode leakage of gyromagnetic stripline can be suppresed by properly choosing the magnetic bias condition and operating frequency. A leaky-wave antenna operated with the first higher-order leaky mode of the gyromagnetic microstrip line is proposed and analyzed. It was shown that the beam angle of such a leaky-wave antenna can be steeered from horizopn to nearly vertical by only varing 6.5% of the DC magnetic bias field Ho.