有限厚度及電導之準平面式傳輸線之近似模型與分析

Abstract

本論文提出一個傳輸線近似模型用以分析實際損耗性準平面式微波及毫米 波傳輸線之傳輸特性，特別是金屬損耗。於此近似模型中，利用多層無限 薄且帶有限導電率之金屬條來模擬損耗性準平面式傳輸線中具有厚度及導 電率之金屬導條。此近似模型結合了全波空間域積分方程式法導出之公式 及一組利用空氣模及金屬模的概念推導而成之基底函數。藉由空氣模及金 屬模構成的完全基底組來描述模型中堆基金屬條上之電流，可解決對於無 厚度而具有限導電率之爭議。也因如此，所要解決的場論問題仍可維持其 一維特性，而整個計算時間可預期地減少。為了要確認所提出之方法的適 用性，文中對收斂性分析及幾種不同結構之準平面式傳輸線如微帶線、耦 合微帶線、槽線、鰭型線及共平面波導等例子分析結果進行報告。應用此 新方法後確可發現，在執行速度上此方法比本實驗室現有全波模匹配法之 程式快上約十倍。 In this thesis, an approximate transmission line model which utilizes stacked metal strips assuming zero thickness and finite conductivity to simulate the metallization with finite thickness and conductivity in the lossy quasi-planar waveguides is presented. The approximate transmission line model is closely associated with a novel full-wave formulation based on a space-domain integral equation method which incorporates the concept of air modes and metal modes to describe the current flow on the stacked metal strips, the controversy caused by the assumptions of zero thickness and finite conductivity can be resolved and the field-theoretic problem remains one- dimensional. Thus, computational time can be significantly reduced. Convergence study and case studies on different kind of transmission structures are conducted to confirm the validity of the proposed technique.Convergence of the numerical results calculated by the present formulation is achieved within a satisfactory range of accuracy. Theoretic results are presented for the cases of microstrip line, coupled strip lines, slotline, finline and coplanar waveguide. Good agreement with nearly all the compared data existing in the literature is shown. The computational time is about one order of magnitude less than that required by conventional full-wave mode-matching program solving the same problem.