A selectivity‐enhancement technique is presented for design of parallel‐coupled stepped‐impedance resonator (SIR) based dual‐band bandpass filter (BPF) in this article. The presented dual‐band BPF consists of two short‐circuited coupled lines (SCCLs) and a couple of parallel‐coupled SIRs. Theoretical analysis and numerical simulations on the proposed parallel‐coupled dual‐band BPF and SCCLs are implemented, respectively. Additionally, by loading the two different SCCLs at the input and output ports of the parallel‐coupled dual‐band BPF separately, two transmission zeros can be created beside each passband, which will enhance the skirt selectivity and stopband performances significantly. For demonstration, a dual‐band BPF prototype with the center frequencies of 2.3 and 4.4 GHz is designed, fabricated, and measured. The measurement results agree well with the simulation ones, which verifies the feasibility of the technique.

中文翻译：

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基于并行耦合SIR的双带通滤波器的选择性增强技术

本文针对基于并联耦合步进阻抗谐振器（SIR）的双带通滤波器（BPF）的设计提出了一种选择性增强技术。提出的双频带BPF由两条短路耦合线（SCCL）和一对并联耦合SIR组成。对所提出的并行耦合双频带BPF和SCCL分别进行了理论分析和数值模拟。此外，通过在并行耦合双频带BPF的输入和输出端口分别加载两个不同的SCCL，可以在每个通带旁边创建两个传输零，这将显着提高裙边选择性和阻带性能。为了演示，设计，制造和测量了中心频率为2.3和4.4 GHz的双频带BPF原型。