设计了一种新的具有良好选择性的小型化的双模双通带带通滤波器。该滤波器的谐振结构由两个短路枝节加载谐振器(SSLR)连接到同一个接地金属柱构成。首先通过奇偶模分析方法分析单个SSLR的谐振频率, 得到谐振频率的变化规律; 然后为了实现滤波器的小型化, 将两个SSLR连接到同一个金属柱上并且折叠微带线, 通过调节枝节长度分析滤波器通带的变化; 设计中使用双枝节分别对谐振器馈电的结构, 并且引入了源与负载耦合, 可以在上阻带多提供一个传输零点, 以提高阻带抑制; 最后对滤波器的传输零点进行分析, 提高滤波器的选择性。通过上述的分析, 对该滤波器进行仿真、加工以及测试, 得到最后实物的测试结果与软件的仿真结果较为一致。

This paper presents the design of a novel dual-mode dual-band bandpass filter with good selectivity. The resonant structure of the filter consists of two short-circuited stub loaded resonators (SSLRs) connected to the same grounded metal column. Firstly, the resonant frequency of a single SSLR is analyzed by odd-/even-mode analysis method and the variation regulation of single SSLR resonant frequency is obtained. Secondly, in order to realize the miniaturization of the filter, two SSLRs are connected to the same metal column and then the microstrip line is folded, and the change in the passband of the filter is analyzed by adjusting the length of the branch. Thirdly, in the design, double-stub feeders are used to feed the two resonators separately and the source-load coupling is introduced, so that an additional transmission zero can be provided in the upper stopband to increase the stop-band suppression. Finally the transmission zeros of the filter are analyzed and the rules of variation are summarized to improve the selection characteristics of the filter. Based on this analysis, the filter is simulated, processed and tested, and the final physical measurement results are consistent with the software simulation results.