一种新型多模三通带滤波器

提出了一种基于多模谐振器的新型三通带滤波器.该滤波器由一个多模谐振器和一对馈线构成,多模谐振器结构具有对称性.利用奇偶模理论分析了该结构的谐振特性.该结构6个谐振模式的频率都可以由对应的物理尺寸自由调节;所有谐振模式的等效电路均为1/4波长谐振器,有效地减小了滤波器的尺寸,实现了小型化.同时,一次谐波出现在三倍频处,使得滤波器拥有良好的带外选择特性.在结构中引入枝节之间的耦合,不仅分离了重合的谐振模式,也形成了两个新的传输零点,进一步提高了通带之间的隔离度.最后设计并加工了一款工作于1.5GHz/2.4GHz/3.5GHz的三通带滤波器,测试与仿真结果吻合良好.

Design of a novel multiple-mode tri-band bandpass filter

A compact tri-band microstrip filter based on an MMR (multiple mode resonator) is presented, which consists of an MMR and a pair of feedlines. Firstly, due to the symmetry of the structure, the even-odd-mode method is applied twice to analysis the resonant characteristics. All the six mode frequencies can be freely tuned by changing the lengths of loaded stubs, and all the four modes equivalent circuits are quarter-wavelength resonators, which largely minimize the size of the filter. Secondly, stub to stub coupling is introduced to split two modes and produce two new transmission zeros with the passband selectivity improved. Finally, a microstrip tri-band bandpass filter (BPF) operating at 1.5GHz/2.4GHz/3.5GHz is designed, fabricated and measured. Measured results are in good agreement with the simulated ones.