In this paper, a microstrip low-pass filter (LPF) using folded-flag-shaped resonators is designed and presented. Its base resonator length is 12.4 mm, and the proposed low-pass filter has a sharpness of 0.08 GHz. The filter cut-off frequency is 1.44 GHz, and the return loss is reduced to a level of −17 dB, indicating a flat pass-band. Also, the suppressing cell is used to weaken the disturbing harmonics by a stepped impedance structure and two high-impedance stubs with an L-shaped structure, which results in a bandwidth of 17.78 GHz. The circuit area of the LPF is 20.9 × 7.5 mm², which it has created a suitable normalized circuit size (NCS) rate due to the −3 dB cut-off frequency. The figure of merit (FOM) of the proposed filter is 114450, and it indicates that the microstrip LPF responses are optimal as compared to previous works.

本文设计并提出了一种采用折叠旗形谐振器的微带低通滤波器（LPF）。它的基本谐振器长度为12.4 mm，建议的低通滤波器的清晰度为0.08 GHz。滤波器截止频率为1.44 GHz，回波损耗降低到-17 dB的水平，表明通带平坦。此外，抑制单元还通过阶梯式阻抗结构和两个具有L形结构的高阻抗短线来减弱干扰谐波，从而产生17.78 GHz的带宽。LPF的电路面积为20.9×7.5 mm ²，由于截止频率为-3 dB，它创建了合适的归一化电路尺寸（NCS）速率。提出的滤波器的品质因数（FOM）为114450，它表明微带LPF响应与以前的工作相比是最佳的。