利用任意映像阻抗設計平行耦合線帶通濾波器

Abstract

本論文提出了一種平行耦合微帶線帶通濾波器電路的設計方法與近似合成公式，每個耦合級的映像阻抗可以是任意值，可大大增加帶通濾波器的設計自由度。我們將這想法應用到兩個實例中，第一是放寬前後級耦合段的線距，以加大平行耦合微帶線帶通濾波器可實現之頻寬；另外一例是利用映像阻抗的改變，抑制濾波器在二倍頻的虛假響應。本文有數個實作電路驗證此一方法及推導的公式，其量測與模擬結果均相一致。

An approximation formulation is proposed for implementing parallel-coupled line filters with arbitrary image impedance. The degree of freedom for the synthesis and design of microstrip filters is thus greatly increased. In this thesis, two applications for this method are reported. One is to relax the gap sizes of the end stages, so that the realizable bandwidth of the band-pass filter can be extended, and the other is to suppress the spurious response of a parallel-coupled microstrip filter at twice the center frequency (2f0). Some experimental filters are fabricated and measured to validate the method and formulation. The simulation and measured results show a good agreement.