具可調傳輸零點之對稱耦合微帶線共振器帶通濾波器之電磁耦合係數萃取

Abstract

本論文提出一種有效的方法，用以萃取耦合對稱微帶線共振器間耦合係數中的電耦合係數與磁耦合係數。此萃取結果可以提供一個額外的電路設計自由度。由實驗結果發現，只要適當地選擇共振器的結構參數，產生預設的電磁耦合係數，可在通帶附近產生一個額外傳輸零點。藉由建立等效電路與其導納矩陣，即可確切闡述耦合係數萃取的理論背景與傳輸零點的控制機制。此外，藉由在耦合級間加入短傳輸線增強共振器間的耦合量，以將額外產生之傳輸零點拉近通帶。本論文以數個實作帶通濾波器電路驗證此方法，量測結果與模擬數據相當一致。

A more effective approach is demonstrated for extracting the electric and magnetic coupling components from the coupling coefficient between two coupled symmetric microstrip resonators. It is found that the extraction provides an extra degree of freedom for circuit design. A transmission zero near passband can be created without any cross-coupling scheme but by properly selecting the electrical parameters of the resonators. An equivalent circuit is derived for characterizing the extraction of the coupling and the control of the zero. Moreover, in order to enhance the electric and magnetic coupling between the two resonators, electrically short coupled-line sections are added to the proposed circuit in order to move the transmission zero toward the passband and to maintain the bandwidth. Three experimental filters are realized and measured to validate the approach.