A compact dual-band bandpass filter (BPF ) based on stepped impedance resonator (SIR ) and defected-feeding structure is investigated in this paper.The SIR with T-stub centrally loaded provides more degrees of freedom to adjust the dual-band resonant frequencies.By combining the SIR with the defected-feeding structure and adjusting their dimensions,the absolute bandwidth can be easily controlled.Transmission zero is derived through simulation due to the combination of SIR and defected -feeding structure.Finally,simulation results show the second passband switched among 1.55GHz,1.75GHz and 2.05GHz with a constant absolute bandwidth of 230MHz ± 5.6％,and the first passband fixed at 0.90GHz with a constant absolute bandwidth of 32MHz.The measurement of the fabricated example shows good agreement with the simulation.%本文研究了一种基于阶梯阻抗谐振器(SIR)和缺陷馈电结构的小型双频带通滤波器(BPF).具有T型中央加载的SIR可以更自由地调整双频谐振频率,SIR和缺陷馈电结构组合,并进行阶数调整,可以很容易控制绝对带宽,仿真得到传输零点.最后,仿真结果显示,恒定绝对带宽在230MHz±5.6％ 的情况下,第二通带可以在1.55GHz,1.75GHz和2.05GHz之间切换,恒定绝对带宽为32MHz的情况下,第一通带稳定在0.90GHz.实际加工的滤波器测量结果与仿真结果吻合较好.
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