Design, Simulation and Implementation of Very Compact Open-loop Trisection BPF for 5G Communications

Abstract

A very compact microstrip open-loop bandpass filter (BPF) with asymmetric frequency response and covering the 3.4 to 3.7 GHz 5G spectrum is presented in this paper. The planar BPF consists of three trisection open-loop ring resonators with 50 Ω transmission lines for input and output terminals. An attenuation zero of finite frequency is successfully generated on the upper edge of the passband to achieve sharper cut-off frequency for the passband. The realization of the microstrip trisection filters not only reduces the size of the layout but also interduces either positive or negative cross-coupling. The cross-coupling coefficients (M ij ) between the poles are optimized to operate at the sub-6 GHz 5G spectrum with appropriate impedance bandwidth. The illustrated BPF is modeled and analyzed using computer simulation technology (CST) tool and is fabricated on a Rogers RO3010 substrate with a relative dielectric constant (e r ) of 10.2 and a very small size of 9.5×6×1.27 mm3. The simulated and measured results show a good agreement.