微型髮夾式諧振器並聯開路殘段實現具有高頻寬截止帶雙頻帶通濾波器

Abstract

本論文提出一微型化髮夾式並聯開路殘段諧振器去設計雙頻帶暨寬截止帶帶通濾波器，其中一開路殘段並聯於中間，而另外兩段則對稱地並聯在諧振器的兩側。利用調整開路殘段的阻抗及長度和並聯的位置使所有的諧振器皆有相同的兩個操作頻率，但是彼此的高階諧振頻率會互相錯開。為了增加壓抑的程度進而拓寬高頻截止帶，由並聯的架構和耦合線段所產生的傳輸零點來消除存餘的高階諧波。五階濾波器的量測結果顯示小於28dB的截止頻帶可以拓展到六倍的基頻頻率。而量測的結果與模擬結果吻合。

Compact bandpass filters are devised with a dual-passband response and a wide upper stopband based on hairpin resonators with three shunt open stubs. One stub is tapped at the center and two are allocated on both sides symmetrically. By adjusting the stub lengths, all resonators are designed to have two identical leading resonant frequencies but different higher-order ones. To enhance the rejection level and extend the upper stopband, the transmission zeros created by the tap structures and the coupled-line stage are used to eliminate the remaining leading unwanted peaks. Measured results show that the fifth-order filter has a rejection level below 30 dB can be extended to six times the first frequency. Good agreement between measured and simulation is obtained.