平衡饋入式帶通濾波天線

Abstract

本論文提出一種將濾波天線與平衡式濾波器整合設計的架構，並稱之為平衡饋入式帶通濾波天線；平衡饋入式帶通濾波天線採用平衡式饋入，且俱有濾波、輻射的效能，平衡饋入式濾波天線同時將傳統射頻前端電路的三種元件(巴倫、濾波器、天線)利用單一元件便可以達成。我們利用兩階的步階式阻抗共振器與倒L型天線設計頻寬25%的三階切比雪夫響應的平衡饋入式帶通濾波天線；步階式阻抗共振器在差模等效半電路為四分之一波長共振，共模共振頻率為半波長共振，共模共振頻率遠離差模共振頻率因此能夠抑制共模訊號。我們分析平衡饋入式帶通濾波天線的等效電路，證明等效電路同帶通濾波器，因此能利用濾波器合成方式設計天線。我們分析等效電路的頻率響應以及，利用全波模擬軟體模擬並實作電路，三者的結果頻寬皆有25%，在通帶內俱有三個極點，模擬與量測的場型皆為全向性。

In the thesis a new microwave device is proposed. The device is combination of balun , filter, matching network and antenna. It filters and radiates simultaneously with balanced feed. The structure of device is two stepped impedance resonator and one inverted-L antenna .The two stepped impedance resonator transform single-end feed inverted L antenna to balanced feed ,and in common mode operate at frequency far away from passband so as to suppress common mode signal . We analyzed the equivalent circuit and showed it is equivalent to bandpass filter.We designed the device with filter specification for 25% bandwidth 3order chebyshev response ,the result of equivalent circuit,simulation and measurement are in good agreement and show good filtering performance. The radiating element of the sructure is a inverted-L antenna so it radiates a omni-directional pattern in principal plane .