In this study, a novel tri-band bandpass filter supported by five resonant modes is developed on the basis of two coupled open-loop resonators with center-loaded bars (CLBs). Embedding the S-shaped resonator into the open-loop structure generates a new passband while keeping the same layout area. Also, another LB located between the open-loop resonator and the CLB is introduced to provide the perturbation for generating new resonances. The final design is realized by the structure optimization via adjusting the coupling coefficients and external quality factors. The measurements match well with the simulation which proves its practicability in (0.45–6 GHz) 5G frequency range-1 (FR-1).

中文翻译：

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由负载棒和嵌入式S形谐振器构成的中心对称耦合三频带通滤波器

在这项研究中，基于两个带有中心加载棒 (CLB) 的耦合开环谐振器开发了一种由五种谐振模式支持的新型三带带通滤波器。将 S 形谐振器嵌入到开环结构中会生成新的通带，同时保持相同的布局面积。此外，位于开环谐振器和 CLB 之间的另一个 LB 被引入以提供用于产生新谐振的扰动。最终的设计是通过调整耦合系数和外部品质因素的结构优化来实现的。测量结果与模拟结果非常吻合，证明了其在 (0.45–6 GHz) 5G 频率范围 1 (FR-1) 中的实用性。