非對稱共平面耦合線於天線應用之分析

Abstract

共平面波導 (Coplanar Waveguide, CPW)至今己廣泛使用於各種微波電路以及元件的設計，為其中一種最基本的傳輸線．過去文獻討論有限/無限接地面的共平面波導、背覆導體的共平面波導、或是更多共平面對稱形金屬板的共平面波導己經有近似的解析解．甚至今日盛行的全波模擬軟體己經可以快速精準的得到任意形式傳輸線的特徵阻抗與等效介電常數．然而對於非對稱共平面波導(即耦合線)，設計者無法給予它單埠的共差模解耦合埠的特徵阻抗以及四埠阻抗參數(Z parameter)，即使全波模擬軟體也沒有直接的萃取方式．本篇論文利用複數分析的保角映射方法得到非對稱共平面耦合線的傳輸線特徵，並使用它來做平面型的天線設計如雙頻天線，空間濾波器與波束切換天線．

So far, the coplanar waveguides (CPW) are extensively used for all kinds of microwave circuits and components, it is one of the most basic transmission lines. In the past, numerous papers had solved the analytical solution for the finite/infinite ground-plane CPW, conductor backed CPW and symmetrical multi-metal-plate CPW. There are many full-wave simulators available for evaluating arbitrarily shaped transmission-line parameters such as characteristic impedance and effective dielectric constant. However, for asymmetrical CPWs (e.g. coplanar coupled line), designers are still unable to obtain the decoupled common/differential-mode port characteristic impedance and four-port Z parameters from commercial full-wave electromagnetic field simulation software directly. This thesis utilizes the conformal mapping method of complex analysis to obtain the decoupled common/differential-mode port characteristic impedance and effective dielectric constant that can be used for planar antenna designs such as dual-band antenna, spatial filter and beam-switching antenna.