In this paper, a balanced dual‐band bandpass filter (BPF) with a high selectivity and intrinsic common‐mode (CM) suppression is presented. The proposed balanced BPF consists of balanced stepped‐impedance microstrip‐slotline transition (BSIMST) structures and two pairs of half‐wavelength split‐ring resonators (SRRs). The designed SRRs can generate two differential‐mode (DM) passbands. By adjusting the widths and lengths of SRRs and the gaps between them, the bandwidths of the two DM passbands can be controlled easily. In order to enhance the filtering performance, the cross coupling and parallel coupling structures are applied to generate transmission zeros (TZs) in this design. Meanwhile, the adoption of source‐load coupling introduces one more TZ, which can improve the selectivity of the DM passbands further. Meanwhile, a good CM suppression is obtained by employing symmetrical BSIMST, which is independent from the DM passbands. Therefore, the design procedure can be significantly simplified. Finally, a balanced dual‐band BPF centered at 1.58 and 2.44 GHz is fabricated and measured to verify the feasibility of the proposed design. A good agreement between the simulation and measurement results is observed.

中文翻译：

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高选择性平衡双频BPF的设计

本文提出了一种具有高选择性和固有共模（CM）抑制能力的平衡双带通滤波器（BPF）。拟议的平衡BPF由平衡的步进阻抗微带-缝隙线过渡（BSIMST）结构和两对半波长开口环谐振器（SRR）组成。设计的SRR可以产生两个差模（DM）通带。通过调整SRR的宽度和长度以及它们之间的间隙，可以轻松地控制两个DM通带的带宽。为了提高滤波性能，在本设计中，采用了交叉耦合和并联耦合结构来生成传输零点（TZ）。同时，采用源-负载耦合引入了另一种TZ，可以进一步提高DM通带的选择性。与此同时，通过采用独立于DM通带的对称BSIMST，可以获得良好的CM抑制。因此，可以大大简化设计过程。最后，制造并测量了以1.58和2.44 GHz为中心的平衡双频段BPF，以验证所提出设计的可行性。观察到仿真结果与测量结果之间的良好一致性。