紧凑型高共模抑制微带平衡滤波器

Design of compact microstrip balanced filter with high common-mode suppression

针对微带平衡带通滤波器结构不紧凑或共模抑制性能不高等问题,提出了一种高共模抑制的紧凑型微带平衡滤波器.首先给出了平衡滤波器的差模和共模等效电路,分析了交指线耦合谐振单元在差模和共模激励下的工作机理;利用该谐振器对共模信号的失配特性和结构紧凑的特点实现了平衡滤波器的高共模抑制和小型化;最后设计并加工了一款工作于2.45GHz的微带平衡带通滤波器,测试与仿真结果吻合良好.

The traditional microstrip balanced bandpass filter （BPF） usually has disadvanteges of large size and low common-mode suppression. This paper presents a novel compact microstrip balanced BPF with improved performance of common-mode suppression. Firstly, it proposes the differential and common-mode equivalent circuits of the balanced BPF. Secondly, a very compact interdigital coupled resonator is analyzed, which has the characteristic of strong mismatch with common-mode signals. By using this novel resonator, a balanced BPF with good performance and miniaturization can be achieved. Finally, a balanced BPF centering at 2.45 GHz is designed and fabricated. Measured results and simulated results are in good agreement.