1、 通带可调节的双通带滤波器通带可调节的双通带滤波器 Dual-Band Filter with Tunable Upper Passband 2011 2011 年年 6 6 月月 I 摘摘 要要 近年来，随着全球定位系统和无线局域网技术的发展，微波系统对双频操作的需 求正在与日俱增。双通带带通滤波器作为微波系统的重要部件，已经变得越来越有研 究价值。最初的双通带滤波器是由两个工作频率不同的单通带滤波器并联而成的。这 种双通带滤波器的两个通带，不论是中心频率还是带宽都容易调节。但是这种结构增 加了电路的插入损耗和尺寸。最终基于双通带滤波器设计理论，设计了一种通带可调 节的双通带滤波器。 它由一
2、对方形开环谐振器和一个对称的阶梯形谐振器互相耦合来 实现，此滤波器工作频率为 1.57GHz和 2.45GHz。第一通带的中心频率取决于方形开 环谐振器的传输线长度和宽度， 第二通带的中心频率和带宽取决于阶梯形谐振器的传 输线长度和宽度。同时，第二通带的频率和带宽能被自由的调节而第一通带的频率和 带宽是固定不变的。而且测试结果显示出所设计的双通带滤波器性能很好。 关键词关键词：带通滤波器；双带；阶梯形谐振器；开环谐振器 II ABSTRACT Recently, with development of global positioning system and wireless local-a
3、rea network, systems demand of radio frequency circuits with a dual-band operation. Dual-band bandpass filters (BPFs), as one the most important circuit blocks in these systems, have become more and more attractive.In general, two filters with different passbands connected together can implement the
4、 initial type of a dual-band filter. The center frequencies and bandwidth have been obtained to meet performance requirements of two passbands. But this solution increases the insertion loss and the overall size of a resultant filter block. Finally, a filter is fabricated based on the design topolog
5、y. A microstrip dual-band bandpass filter is developed in this letter. Using a pair of square open-loops coupled with a symmetric ladder-shaped resonator, frequencies of this filter are operated at 1.57GHz and 2.45GHz. The lower resonance frequency is decided by the length of the square resonators,
6、and the higher one is done by the ladder-shaped resonator. Therefore, both frequency and bandwidth of the upper passband can be controlled flexibly, whereas those of the lower band are fixed. Measured results have shown very good performance of the filter. Key Words：Bandpass filter；dual-band；adder shaped resonator；pen-loop resonator III 目 录 1 绪论 . 1 1.1 微波滤波器的发展 . 1 1.2 滤波器在微波通信的作用 5 1.3 本论文研究的内容 6 2 微带线 . 8 2.1 介质微带线和微耦合带线 . 8 2.1.1 介质微带线 . 8 2.1.2 微带耦合线 10 2.2 微带谐振电路 13 2.2.1 谐振原理 .
