Band Pass Filter Utilizing a Stepped Impedance Resonator for Modern Wireless Communication System

Abstract

This study presents the design and evaluation of a second-order dual-band bandpass filter (DBPF) for modern wireless communication systems. The proposed filter employs meandered-shaped stepped impedance resonators (MSIRs) to achieve compact size and enhanced performance. The first band operates at 2.6 GHz with a fractional bandwidth (FBW) of 18%, while the second band is centered at 4.37 GHz with an FBW of 11%. Three transmission zeros (TZs) are strategically positioned to improve the filter's selectivity. The filter is implemented on Rogers RO 4350C substrate with εᵣ = 3.66, tan δ = 0.001, and thickness h = 0.762 mm, resulting in an overall filter area of 49 × 30 mm² (0.7λg × 0.47λg at 2.6 GHz). CST Studio Suite 2019 was utilized for electromagnetic analysis. Simulation results demonstrate low insertion loss (IL) and high return loss (RL) at both operating bands, achieving IL of 0.2 dB and RL of 16.7 dB for the first band, and IL of 0.6 dB and RL of 11.3 dB for the second band. The transmission zeros are located at 1.93, 3.71, and 4.83 GHz, respectively. The proposed filter operates with quasi-independent dual-band functionality, which can be controlled by adjusting the section lengths of the SIR