具有陷波特性的双通带滤波器设计

Design of a Dual-Passband Filter with a Notch Property

摘要:

提出了一种具有陷波特性的双通带滤波器,并利用奇偶模理论分析了该滤波器的传输特性。滤波器由倒π型谐振器、T型谐振器和输入输出并联馈线组成,同时在倒π型谐振器枝节上加载阶跃阻抗(SIR)抑制第一通带的二次谐波。通过对滤波器进行整体仿真并优化其陷波频率和深度,最终得到的陷波频率分别为1.8 GHz和 6.7 GHz,且深度均达到-19 dB以下。最后对双通带滤波器进行实物加工和测试,得到两个通频带分别为1.44~ 2.4 GHz、5.4~7.4 GHz,通带内插入损耗分别为-1.16 dB和-1.6 dB,通带间隔离度最大可达50 dB。实测结果与仿真结果吻合良好,验证了所提滤波器结构和设计方法的可行性。

Abstract:

A dual-passband filter with a notch is proposed. The transmission characteristics of the filter are also analyzed using the odd-even mode theory. The filter is composed of an inverted π resonator, a T-resonator, and an input and output parallel feeder. A step impedance (SIR) is loaded on the branches of the inverted π resonator to suppress the second harmonic of the first passband. Through the overall simulation of the filter and the optimization of its notch frequency and depth, the final notch is located at 1.8 and 6.7 GHz, and the depth can reach less than-19 dB. Finally, the dual-passband filter was processed and tested. The two passbands are 1.44-2.4 and 5.4 7.4 GHz. The insertion loss in the passband is -1.16 and -1.6 dB, and the maximum isolation between the pass bands is 50 dB. The measured results agreed well with the simulated results, thus verifying the feasibility of the structure and design method proposed in this study.