In this paper, a miniaturized tri-band bandpass microstrip filter using stub loaded rectangular ring resonator (SLRRR)，shorted stub loaded stepped impedance resonators (SSLSIR), and stepped impedance resonators (SIR) with sharp skirts is presented. Two SSLSIRs are embedded paralleled inside SLRRR to generate a quasi-elliptic response at second and third passband. The odd-even fundamental resonant mode and first high-order resonant mode of the SIRs are exploited to generate tri-band response. Three bandwidths can be controlled independently due to different signal paths. Extra transmission zeros are introduced by the configuration of 0° feed structure. Sharp skirts are achieved at the upper edge of each passband by λg/4 lines which are loaded at the I/O ports. An example of the proposed tri-band filter operating at 2.76 GHz/5.7 GHz/7.63 GHz for TDD-LTE/WLAN/VSAT applications is implemented and fabricated. The simulation and measurement show a good agreement.

中文翻译：

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使用带尖裙的多个谐振器的小型化三频带带通微带滤波器

本文提出了一种使用短截线加载矩形环形谐振器（SLRRR）、短截截线负载阶梯式阻抗谐振器（SSLSIR）和带尖裙的阶梯式阻抗谐振器（SIR）的小型三频段带通微带滤波器。两个 SSLSIR 并行嵌入 SLRRR 内部，以在第二和第三通带产生准椭圆响应。利用 SIR 的奇偶基本谐振模式和第一高阶谐振模式来产生三频带响应。由于信号路径不同，可以独立控制三个带宽。0°馈电结构的配置引入了额外的传输零点。通过在每个通带的上边缘实现锋利的裙边λG/4 行在 I/O 端口加载。实施和制造了一个针对 TDD-LTE/WLAN/VSAT 应用在 2.76 GHz/5.7 GHz/7.63 GHz 工作的建议三频滤波器的示例。仿真和测量显示出良好的一致性。