一种基于SIR结构的三通带带通滤波器

应用双指耦合结构和枝节加载谐振器（Stub-loaded Resonator，SLR）实现了一款基于阶梯阻抗谐振器（Stepped Impedance Resonator，SIR）的滤波器。该滤波器具有3个通带，带外抑制较好，工作频段提高。通过调整阻抗比可调节第二、三通带的谐振频率；SLR结构能够增加通带数量；SLR结构和双指耦合结构均能改善滤波器的S参数。HFSS软件仿真表明，3个通带的中心频率分别为3.5 GHz、6.6 GHz、9.2 GHz，对应的分数带宽分别为5.7%、3%、2%，S11分别为-18 dB、-22 dB、-24 dB，通带内的S21分别为-1.8 dB、-1 dB、-1 dB。电路的测量结果与仿真结果较为吻合。该滤波器在5G通信的低频段具有应用前景。

A three-pass bandpass filter based on SIR structure

By using a two-finger coupling structure and a stub-loaded resonator (SLR),a filter based on a stepped impedance resonator (SIR) with three passbands,better out-of-band rejection,and improved operating frequency band is implemented.The resonant frequency of the second and the third bandpass be adjusted by adjusting the impedance ratio.SLR structure can increase the number of passband.Both the SLR structure and the two-finger coupling structure can improve the S parameters of the filter.The simulation with HFSS software shows that the central frequencies of the three passbands are 3.5 GHz,6.6 GHz and 9.2 GHz respectively,the corresponding fractional bandwidth is 5.7%,3% and 2%,respectively;the S11 is better than -18 dB,-22 dB and -24 dB,respectively;the S21 in the passband is better than -1.8 dB,-1 dB and -1 dB,respectively.The measurement results of the circuit are in good agreement with the simulation results.The filter can be used in 5G communication.