雙頻濾波器之設計~利用貫孔牆類波導結構

Abstract

本論文提出一個具轉角設計的雙頻濾波器。由於這個轉角的設計，發現在不影響濾波器的雙頻通帶響應下，其高頻諧波響應有將-30dB的抑制,且我們可調整共振腔的長度來控制第二個頻道的頻率。同時，可藉由改變共振腔來得到想要的頻寬。為了證明所提出濾波器有以上的特性，我們實作四個有不同共振腔長度的濾波器，由量測的結果說明，這種有轉角的雙頻濾波器，其高頻諧波平均可以抑制在-25dB以下。

In this thesis, we proposed a planar dual-bandpass filter with bend design. With this bend structure, the higher harmonics response of the proposed dual-bandpass filter can have a suppression of nearly -30dB; meanwhile, the first and the second pass-band specifications remain unchanged. Besides, we found that the second pass-band frequency is tunable by adjusting the length of each cavity. In order to demonstrate the proposed filter performance, four filters with different cavity length were implemented on a low-loss dielectric substrate. In addition to changing the length of each cavity, we changed the aperture length to observe the variation of pass-band bandwidth. From the simulated and measured results, the proposed filter obtains more than -25 dB suppression in average. The measurement shows a very good agreement with simulation.