A simple and modular quasi stepped impedance resonator based reconfigurable bandpass filter for 5G applications

A small-sized quasi-stepped impedance resonator (SIR) based single-band to dual-band reconfigurable bandpass filter is presented in this work. The proposed quasi-SIR filter is modular in nature and can be easily scaled to higher- or lower-frequency bands. To this end, a single- to dual-band reconfigurable modified SIR is designed. The designed reconfigurable resonator was then used to develop a single-band to dual-band reconfigurable filter. The proposed filter structure comprises two resonators loaded with PIN diodes to provide the switching. The filter allows switching between single and dual-band frequencies. In the OFF state, PIN diodes provide single-band resonance with a resonant frequency of 3.8 GHz. While the ON state of PIN diodes provides dual-band resonance of 3.35 GHz and 4.3 GHz. The structure of the filter is modular and is designed, analysed, and fabricated on a low-cost FR4 dielectric substrate with a 4.3 dielectric constant and 0.78 mm thickness. The measured results are in good agreement with the simulation results. The filter is designed to operate in the sub-6 GHz band, a designated band for 5G communication, and is thus suitable for incorporation in 5G devices with reconfigurability applications.