二種具高止帶或低止帶傳輸零點的微帶線濾波器之設計與應用

Abstract

本論文提出二種微帶線濾波器架構來產生低止帶或高止帶有限頻率傳輸零點。其中一種為交錯耦合濾波器，我們利用改變交錯耦合線段長度，即可設計傳輸零點產生的位置。另一架構利用開路支線型態之阻抗轉換器實現四分之一波長平行耦合濾波器，藉由設計開路支線長度可決定傳輸零點所在頻率。如此，我們可以縮小電路面積並且對通帶之外頻率也提供相當抑制能力。同時，利用此濾波器的良好特性設計頻率雙工器。

Two types of microstrip filters with lower- or upper-stopband finite frequency transmission zeros are presented in this paper. One configuration is cross-coupled filter. We can design to have a transmission zero on the lower- or upper-stopband by just adjusting the length of the cross coupling strip. Another one is quarter-wave parallel coupled filter with open stub type K-inverter. We can design the frequency of the transmission zeros by determining the length of the open stubs. Therefore, the size of the filter can be reduced. Also, the out of band signal can be suppressed to a certain value. We use the good performance of the filters designing a diplexer additionally.