Ka頻段高拒斥力波導濾波器

Abstract

本論文使用波導結構發展適用於高性能Ka頻段微波接收機之高拒斥力波導濾波器。為達Ka頻段高拒斥力濾波器之性能，我們選擇使用波導濾波器，有較高的Q值，達到高拒斥力性能。而因應縮小化之要求，可採用最低之不對稱結構為三階結構。三階結構可利用主耦合與交錯耦合電壓之反相，產生有限頻率之傳輸零點，以消去高頻端(或低頻端)之鏡像頻率。所提出的三種形式之三階交錯耦合濾波器，的確皆有比柴比雪夫響應濾波器有較好的頻率選擇性。 波導濾波器採用的耦合結構為常用之電感性孔隙(磁性孔隙)。其輸出入波導為標準的WR-28 Ka 頻段波導。

In this project, the waveguide structures are used to develop the high performance Ka band microwave filters suitable for receiver application. The high performance filter means that it has high rejection capability at specified frequency band and low insertion loss in the pass-band. To reach this goal, higher Q value of the resonators in the filter structures is necessary. The waveguide cavity is chosen to meet the requirement. Furthermore, for the miniaturization, the least possible order of a filter is the asymmetrical third-order structure. It utilizes the phase difference of the main coupling and the cross coupling to produce the finite frequency transmission zeros to eliminate the lower band or higher band image frequency. Three types of third-order cross-coupled filters are proposed that they both have better frequency selectivity than the conventional Chebyshev response filter. The inductive irises (magnetic irises) are used as the general coupling structure in the proposed filters. The I/O waveguide is the standard WR-28 Ka band waveguide.