This letter presents wideband differential-mode (DM) bandpass filters (BPFs) designed on a microstrip line for ultrawideband (UWB) applications. The proposed design is based on an optimized branch-line structure with extended transmission lines (TLs). An enhanced performance can be obtained using a very simple design approach. The introduced TLs can be used for improving the DM stopband response by introducing multiple transmission zeros (TZs) at the lower and upper stopband. The common-mode rejection level can also achieve around 40 dB within the band of interest. The proposed filters are fabricated for experimental verification. The predicted and measured results show a very good agreement.

中文翻译：

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具有阻带和共模抑制功能的宽带差模带通滤波器

这封信介绍了在微带线上为超宽带 (UWB) 应用设计的宽带差模 (DM) 带通滤波器 (BPF)。建议的设计基于具有扩展传输线 (TL) 的优化分支线结构。使用非常简单的设计方法可以获得增强的性能。通过在下阻带和上阻带处引入多个传输零点 (TZ)，引入的 TL 可用于改善 DM 阻带响应。在感兴趣的频带内，共模抑制水平也可以达到大约 40 dB。所提出的过滤器是为实验验证而制造的。预测和测量结果显示出非常好的一致性。