以微小形微帶共振子設計微波濾波器─從窄頻帶到寬頻帶

Abstract

本文利用髮夾型及開迴路方形共振子，藉由調整相鄰共振子之間的耦合，設計具有單一傳輸零點的橢圓函數響應的平面微帶濾波器。此電路結構利用適當的交叉耦合，實現單一傳輸零點，以增加通帶邊緣的頻率選擇性。文中用網路合成技術，由給定的頻率響應函數計算出所需的耦合係數，再利用電磁模擬軟體，決定耦合共振子之間的適當距離，以完成整個電路的佈局。文中設計並製作4%, 10%及25%頻寬的帶通濾波器，並與實際量測結果比較。

Four–pole cross-coupled planar microwave filters are designed using hairpin resonators and square open-loop resonators. It is shown that the filter allows nonadjacent electromagnetic couplings to be adjusted and realized. A single transmission zero is realized by the cross coupling in the structure, which can improve the skirt selectivity of the filter. The synthesis technique for the design of filter is described. The coupling coefficients for the three basic coupling structures are then determined by the filter specification. The full-wave simulator IE3D is used to design the resonators and the three basic coupling structures. Experimental results are compared with computed responses.