使用步階式阻抗耦合線設計之平行耦合線濾波器

Abstract

本論文提出使用步階式阻抗耦合線(stepped-impedance coupled line)結構來設計平行耦合線濾波器，此耦合線結構之電路特性在中心頻可等效成傳統四分之一波長耦合線。本論文分別提出半波長與四分之一波長平行耦合線濾波器，將傳統耦合線取代成步階式阻抗耦合線，實現出半波長步階式阻抗平行耦合線濾波器、四分之一波長步階式阻抗平行耦合線濾波器。提出之濾波器設計除了達到電路縮小化之效果外，也將電路之第一贅頻響應推至三倍基頻以上，使濾波器擁有良好的寬截止頻帶與止帶拒斥特性。

In this thesis, a stepped-impedance coupled line (SICLN) structure is proposed to design the parallel coupled line filters. The proposed SICLN can be equivalent to a conventional quarter-wave coupled line section at the center frequency. The proposed SICLN half- and quarter-wave parallel-coupled filters are implemented by changing the corresponding conventional quarter-wave coupled-line sections in filters to the SICLNs. The proposed filters sizes are reduced while the first spurious responses can be pushed away over three times from the fundamental frequency. Therefore, the proposed filters show wide stopband and good stopband rejection.