電磁耦合係數在微帶線耦合共振器之萃取及其於帶通濾波器之應用

Abstract

本論文提出一種萃取電與磁耦合參數的步驟，其在微帶線耦合共振器中可以將電耦合及磁耦合分離。經由電與磁耦合參數的計算，可推導出整體的耦合係數，並藉此設計一個可調整頻率之傳輸零點的帶通濾波器。靠著適當設計二階或三階濾波器之共振器間的電耦合與磁耦合，產生的傳輸零點可以在通帶的高頻或低頻。藉由等校電路與其導納矩陣，說明零點的控制。另外，本文也提出斜對稱饋入的等效電路，以說明額外產生的兩個傳輸零點。本論文實作數個電路以資驗證設計，量測數據與模擬結果相當一致。

An extraction process is proposed to identify the electric and magnetic coupling between two coupled microstrip resonators. The coupling coefficient is calculated based on the electric and magnetic coupling and used to design bandpass filters with a tunable transmission zero near the passband without any cross coupling. The transmission zero can be placed at either the upper or lower rejection band by properly designing the electric and magnetic coupling of resonators for second- and third- order filters. An equivalent circuit together with its Y-matrix formulation is also developed for explaining the control of the zero. An equivalent circuit model for skew symmetric feed is also proposed for explaining two extra transmission zeros by the tapped-input/output structure of a third-order filter. Theoretical prediction is validated by measurement results of experimental circuits.