In this letter, an ultra-wide band bandstop filter (BSF) with three transmission zeros and one reflection zero is presented. The role of the circular etched shaped stub as a notch pass response is investigated. Further, a compact size of 13 mm × 24.30 mm (0.219λ_g× 0.410λ_g) is achieved by employing an interdigital capacitor to increase coupling between the lines. Furthermore, the transmission line model of the filter is proposed, and consequently even and odd mode impedance is calculated analytically. The proposed filter offers an ultra-wide bandwidth of 6.1 GHz (3.7 GHz-9.8 GHz) with a rejection depth of 20 dB over the entire rejection band. Moreover, the upper skirt factor of 47.2 dB per GHz is achieved. A prototype of the proposed BSF is fabricated and measured. Simulated and measured results are in good agreement which validates the proposed design.

中文翻译：

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带有圆形蚀刻短截线谐振器的超宽带带阻滤波器

在这封信中，介绍了一种具有三个传输零点和一个反射零点的超宽带带阻滤波器 (BSF)。研究了圆形蚀刻形状的短截线作为凹口通过响应的作用。此外，13 mm × 24.30 mm (0.219λ _g × 0.410λ _g) 是通过使用叉指电容器来增加线之间的耦合来实现的。此外，提出了滤波器的传输线模型，从而解析计算偶模和奇模阻抗。建议的滤波器提供 6.1 GHz (3.7 GHz-9.8 GHz) 的超宽带宽，在整个抑制频带内具有 20 dB 的抑制深度。此外，还实现了每 GHz 47.2 dB 的上边缘系数。制造并测量了所提出的 BSF 的原型。模拟和测量结果非常一致，这验证了所提出的设计。