具有寬截止頻帶與平坦群延遲之寬頻帶通濾波器

Abstract

本論文主題是利用鼠競環搭配數節短路殘段和數節開路殘段的架構，設計偶數階和奇數階的柴氏響應寬頻帶通濾波器，並具有平坦群延遲特性和寬截止頻帶，其中心頻率為3GHz，比例頻寬可達100%。 首先，藉由濾波器函數合成和電路分析，設計寬頻帶通濾波器的各段傳輸線阻抗，並求得此結構的零點位於虛頻率軸上，因此能使群延遲平坦。再運用等效電路的方法設計此寬頻帶通濾波器各段傳輸線之步階阻抗架構，以達到寬截止頻帶的效果，更能有效縮小電路面積。在電路佈局方面，利用共平面波導(CPW)，設計50Ω輸入端與輸出端饋入結構，電路則以共平面帶線(CPS)實踐，板材使用厚度為15毫英吋，介電係數為9.8之陶瓷基板(Al2O3)。

This thesis uses wideband hybrid ring with short and open stubs to design even and odd mode Chebyshev wideband filters. The characteristics of the wideband filters include wide stopband and flat group delay. The filters in this thesis are operated at central frequency 3GHz with nearly 100% bandwidth. According to the synthesized filtering functions and by analyzing the corresponding circuit, the impedance of each transmission line section can be determined. The circuit shows pairs of pure-imaginary transmission zeros that can improve the group delay flatness. Using equivalent circuit designs stepped impedance structure of wideband filters for wide stopband and miniature size. All of the circuits are fabricated on Al2O3 substrate with dielectric constant 9.8 and 15mil thickness. We utilize coplanar waveguide (CPW) structure for 50Ω input and output ports, and use coplanar stripline (CPS) implementation.