平衡式双通带独立可控带通滤波器

提出一种基于多模谐振器的平衡式双通带带通滤波器。该设计合理利用谐振器和加载枝节的长度分别调节2个通带的中心频率；利用金属化通孔耦合以及谐振器之间的宽边耦合分别控制2个通带的耦合系数；通过控制馈线与谐振器以及与加载枝节之间的间距分别控制2个通带的外部品质因数，最终实现双通带频率和带宽的独立控制。为了验证所提出的结构，设计了一款平衡式二阶带通滤波器，其测试与仿真结果较吻合，表明了滤波器具有较好的差模通带性能以及良好的共模抑制能力。

Balanced bandpass filter with independently controllable dual passbands

In this paper, a balanced dual-band bandpass filter (BPF) based on multi-mode resonators is proposed. By adjusting the length of the resonator and the loaded stub, the center frequencies of the two passbands can be controlled individually. The coupling of the two passbands can be controlled independently by the via-coupling and broadside coupling. The external quality factor can be adjusted by the distance between the feeding line and the resonator as well as that between the feeding line and the loaded stub. Therefore, the frequencies and the bandwidths of the two passbands can be controlled independently. For demonstration, a second-order balanced BPF is designed. The simulation and measurement results of the proposed filter are in good agreement. The results show the good differential-mode passband performance and good common-mode suppression.