雙耦合微帶線低通濾波器設計

Double Coupled-Line Low-Pass Filter Design

本文提出雙耦合微帶線低通濾波器的設計，此低通濾波器由兩對耦合微帶線相互連接組合而成。此低通濾波器具有接近截止頻率陡直響應特性、結構簡單、低介入通帶損失與小的電路尺寸之優點。濾波器的特性分析以耦合傳輸線等效模型電路進行，並運用所得之設計公式進行3-dB 截止頻率為2.45 和5.2GHz 低通濾波器設計，電氣特性以電磁軟體（IE3D）進行模擬，實際電路以微帶線結構製作。由模擬電路與實際電路之頻率響應驗證本電路設計流程之正確性，結果顯示實際量測與模擬結果具有相當之一致性。

In this paper, we propose a double coupled-line low-pass filter design.The filter consists of two coupled lines connected end-to-end with a commonpoint. The low-pass filter has a sharp slope response near the 3-dBfrequency cutoff point, low passband insertion loss, and compact size. Thecircuit analysis was performed by a coupled transmission line and a T-typeequivalent circuit, and the circuit was evaluated by an electromagneticsimulator, IE3D. Two low-pass filters with 3-dB cutoff frequency at 2.45and 5.2GHz were designed and measured. The measured and simulated resultsshow good agreement in the frequency range from 0.1 to 13GHz.