A microstrip-based lowpass filter (LPF) containing modified ring structures has been presented. Ring resonators are used to form a sharp transition region. In addition, rectangular- and tapered-shaped suppressing cells are used to create an ultra-wide stopband region. By combining the designed ring resonator and suppressors, an LPF has been designed with −3 dB cut-off frequency at 1.83 GHz. A sharp transition region has been achieved from 1.83 (at −3 dB) to 2.1 GHz (at −60 dB). A stopband region has been concluded from 2 to 21 GHz (with the corresponding attenuation level of at least 20 dB). The measured insertion loss is better than 0.1 dB (equal to a return loss of 18.1 dB) in the passband region. The proposed circuit is fabricated and measured. The measured results have an appropriate adaption with the simulated results.

中文翻译：

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使用环形谐振器的超宽阻带低通滤波器

提出了一种基于微带的低通滤波器 (LPF)，其中包含改进的环形结构。环形谐振器用于形成尖锐的过渡区域。此外，矩形和锥形抑制单元用于创建超宽阻带区域。通过结合设计的环形谐振器和抑制器，LPF 设计为在 1.83 GHz 处具有 -3 dB 截止频率。从 1.83（在 -3 dB 处）到 2.1 GHz（在 -60 dB 处）实现了一个急剧的过渡区域。从 2 到 21 GHz（相应的衰减水平至少为 20 dB）已经得出了一个阻带区域。在通带区域测得的插入损耗优于 0.1 dB（等于 18.1 dB 的回波损耗）。所提出的电路是制造和测量的。测量结果与模拟结果有适当的适应。