The design and implementation of the filters for the fifth-generation (5G) mobile communication systems are challengeable due to the demands of high integration, low-cost, and high-speed data transmission. In this paper, a dual-wideband bandpass filter (BPF) and a tri-wideband BPF for 5G mobile communications are proposed. The dual-wideband BPF consists of two folded open-loop stepped-impedance resonators (FOLSIRs), and the tri-wideband BPF is designed by placing a pair of folded uniform impedance resonator inside the dual-wideband BPF with little increase in the physical size of the filter. By employing a novel structural deformation of a stepped-impedance resonator, the FOLSIR is achieved with a more compact structure, a controllable transmission zero, and an adjustable resonant frequency. The measurement results show that the working bands of the two filters are 1.98–2.28/3.27–3.66 GHz and 2.035–2.305/3.31–3.71/4.54–5.18 GHz, respectively, which are consistent with the full-wave EM simulation results. The implemented filters have a compact size and the results show low loss, good out-of-band rejection, and wide passbands covering sub-6 GHz bands of 5G mobile communications and a commonly used spectrum.

This article presents a compact 5G dual‐wideband bandpass filter (DBPF) based on high‐conductivity graphene assembled films (GAFs), which can meet the requirements of the sub‐6 GHz bands, high integration and high information transmission rate for 5G wireless communication. The GAF DBPF consists of two folded open‐loop stepped‐impedance resonators with a compact size of 21.9 mm × 22.5 mm × 0.53 mm. The measured results show that the presented GAF DBPF has two passbands with 3 dB fractional bandwidths of 15.95% and 12.72% at center frequencies of 2.14 and 3.5 GHz, respectively. In addition, the filter exhibits an attenuation level greater than 20 dB up to 7.52 GHz.