用以遮蔽導波管對封裝微帶電路之雜散模的簡單而有效方法

Abstract

在這篇論文中,我們提出一種簡單的結構--在中心微帶線兩旁,對稱 地加上兩小 片金屬薄片--,並且分析此種結構如何屏蔽導波管封裝微 帶線電路中的高階模。 我們將分析兩種大小不同的導波管封裝,並比 較它們的結果。首先,我們用二維 有限元素法和線方法來研究封裝微 帶線兩旁加上無限長金屬片的結構,求得此結 構中模的等效介電常數 和場形分佈對於金屬寬度的變化。由此結果,我們得知有 一段金屬寬 度區間,會使得此結構中高階模的場形完全不同於未加金屬片微帶線 中模的場形。接著,我們用邊元素的三維有限元素法來分析金屬片寬度和 長度對 於金屬片散射效應的影響。由此結果,我們可以適當地選擇金 屬片的大小,並以 此種簡單的結構完全地屏蔽寄生的高階模而不影響 主模的正常傳播。 A simple structure formed by two metal patches symmetrically deposit- ed at the two sides of the center microstrip is proposed and analyzed for shielding the higher- order modes in a waveguide-packaged micro- strip line circuit. Two packaging waveguide sizes were considered and compared. The variations (with the patch width) of the effective die- lectric constants and field distributions, of the modes in the pack- aged microstrip line with infinitely long side patches, were first investigated using the 2-D finite element method and the method of lines. The results suggested that there exists a range of patch width at which the field distributions of the higher-order modes are total- ly different from those of the microstrip line without side patches. The scattering of the patches, as a function of the patch length and width, was then studied using the 3-D finite element method with edge elements. It has been found that, by simply choosing appropriate patch sizes, the parasitic higher-order modes can completely shielded without sacrificing the normal propagation of the dominant mode.