基于U形可调耦合环的全可调带通滤波器

A Fully Tunable Bandpass Filter Based on U-structure Tunable Coupling Ring

传统的可调滤波器设计通常采用插入可变电容的方式实现可调滤波,但存在设计复杂度高的弊端。结合同轴线谐振腔以及微带线工作特点,设计一种基于U型可调耦合环的完全可调带通滤波器。通过加载变容二极管实现通带中心频率和通带带宽的独立调节,并结合实验分析了U型可调耦合环的工作原理。设计、制作并且测量由5个全可调谐谐振器级联组成的全可调谐滤波器,中心频率在400~530 MHz范围内可调,带宽在6~16 MHz范围内可调;且中心频率调节时插入损耗小于2 dB,带宽调解时插入损耗小于3.5 dB。

Traditional tunable filter is often designed by tunable filtering with variable capacitors, but there is a drawback of high design complexity. A fully tunable bandpass filter structure based on U-structure tunable coupling ring is proposed. By loading varactor diode, the center frequency and bandwidth of passband can be adjusted independently, and the working principle of U-structure tunable coupling ring is analyzed. Finally, a fully tunable filter composed of five fully tunable resonators is designed, fabricated and measured. The center frequency is tunable in the range of 400~530 MHz. And the bandwidth is adjustable in the range of 6~16 MHz. The insertion loss of frequency tuning is less than 2 dB, the insertion loss of bandwidth tuning is less than 3.5 dB.