In this article, a tunable lowpass filter (LPF) with a hexagonal stepped impedance resonator and multi open stubs is designed. The − 3 dB cut-off frequency for the proposed LPF is 2.2 GHz. Insertion loss (IL) and return loss (RL) in the passband zone are 0.3 dB and 15 dB, respectively. The frequency response slope (roll-off rate) for the proposed LPF is very sharp and equal to 142.4 dB/GHz. The tuning range of − 3 dB cut-off frequency for the presented LPF is very wide and equal to 2.7 GHz [from 0.5 to 3.2 GHz (84.3%)]. To achieve the desired structure and harmonics suppression, a conventional power divider was designed initially, then the transmission lines (with length of λ/4) were replaced with two LPFs. The isolation, IL, and input RL for the proposed modified Wilkinson power divider are better than 20.1 dB, 3.1 dB and 21.2 dB, respectively, at operating frequency of 1.8 GHz (GSM band). The proposed modified Wilkinson power divider eliminates the 2nd–11th harmonics with high levels of attenuation. The feature selective validation method depicts that the simulation and measurement results for the proposed LPF are in good agreement with each other.

在本文中，设计了具有六角形步进阻抗谐振器和多个开路短截线的可调低通滤波器（LPF）。拟议的LPF的− 3 dB截止频率为2.2 GHz。通带区域的插入损耗（IL）和回波损耗（RL）分别为0.3 dB和15 dB。拟议的LPF的频率响应斜率（下降率）非常陡峭，等于142.4 dB / GHz。所提出的LPF的− 3 dB截止频率的调谐范围非常宽，等于2.7 GHz [从0.5到3.2 GHz（84.3％）]。为了实现所需的结构和抑制谐波，最初设计了常规功率分配器，然后将传输线（长度为λ/ 4）替换为两个LPF。提议的改进的威尔金森功率分配器的隔离度，IL和输入RL分别优于20.1 dB，3.1 dB和21.2 dB，工作频率为1.8 GHz（GSM频段）。提出的改进的威尔金森功率分配器消除了具有高衰减水平的2-11次谐波。特征选择验证方法表明，所提出的LPF的仿真和测量结果相互吻合。