雙頻可開關式頻率可調濾波器

Abstract

本論文提出可開關的雙頻頻率可調濾波器，結合開關與可調濾波器，運用鑲嵌在濾波器結構中的變容二極體的特性，透過改變變容二極體的偏壓，作為關閉、單頻與雙頻三種組態的切換方法。 本設計以柴比雪夫二階濾波器為理論基礎，加上逆偏壓操作之變容二極體其電容值隨偏壓而改變的特性，構成頻率可調濾波器，並且以五十歐姆傳輸線並聯兩組濾波器，形成可雙頻操作的結構。整體電路以微帶線實現，使用的基板為Rogers RO4003C，厚度為20 微英吋，介電係數為3.55。

In this study, a switchable and tunable dual-band filter is proposed. Combining switches and tunable filters, the circuit can operate in three different modes (off / single-band / dual-band) by changing the bias of varactors embedded in the structure. The design of tunable filter is based on second-order type I Chebyshev filters and vatactors which can be considered as voltage-controlled capacitors. The structure of dual-band filter is formed by connecting two filters in parallel with 50-ohm lines. The circuit in this study is fabricated with microstrip line on a RO4003C substrate with thickness of 20 mil and dielectric constant of 3.55.