This article presents a balanced tri‐band superconducting band‐pass filter (BPF) with controllable center frequencies (CFs) and fractional bandwidths (FBWs) using novel double square ring loaded resonators (DSRLRs). Due to the symmetrical structure of the proposed DSRLR, the differential mode (DM), and common mode (CM) equivalent circuits of the resonator are analyzed by using even‐ and odd‐mode methods, and the resonant characteristics can also be obtained. With the proper design of the proposed DSRLR, the first three DM resonant frequencies are utilized to construct the three DM passbands, and their CFs can be adjusted by changing the lengths of the corresponding stubs. Then, the internal coupling between resonators can be controlled independently by the additional capacitive loading microstrip and the interdigital coupling structure. In addition, the so‐called frequency dispersion technique is used to enhance CM suppression in the proposed balanced tri‐band BPF by loading additional multiple stubs on the symmetry plane. Consequently, the proposed tri‐band BPF can realize controllable CFs and FBWs with broadband CM suppression. Prototype balanced filters with CFs of 1.7/2.45/3.4 GHz and FBWs of 2.9%/3.2%/1.8% were designed, manufactured, and measured for verification. The experimental results agree well with the simulated ones.

中文翻译：

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使用双平方环负载谐振器的紧凑型平衡三频超导带通滤波器

本文介绍了使用新型双平方环负载谐振器（DSRLR）的具有可控中心频率（CF）和分数带宽（FBW）的平衡三频超导带通滤波器（BPF）。由于所提出的DSRLR的对称结构，使用偶数和奇数方法分析了谐振器的差模（DM）和共模（CM）等效电路，并且还可以获得谐振特性。通过建议的DSRLR的正确设计，可以利用前三个DM谐振频率来构建三个DM通带，并且可以通过更改相应短截线的长度来调整它们的CF。然后，可以通过附加的电容性负载微带线和叉指耦合结构独立地控制谐振器之间的内部耦合。另外，通过在对称平面上加载额外的多个短截线，所谓的频散技术被用于增强建议的平衡三频带BPF中的CM抑制。因此，提出的三频BPF可以实现具有宽带CM抑制的可控CF和FBW。设计，制造和测量了具有1.7 / 2.45 / 3.4 GHz CF和FBW 2.9％/ 3.2％/ 1.8％的原型平衡滤波器，以进行验证。实验结果与模拟结果吻合良好。设计，制造和测量了4 GHz和2.9％/ 3.2％/ 1.8％的FBW，以进行验证。实验结果与模拟结果吻合良好。设计，制造和测量了4 GHz和2.9％/ 3.2％/ 1.8％的FBW，以进行验证。实验结果与模拟结果吻合良好。