Design of Single-Cavity Dual-Band Filter Based on Stepped Impedance Resonators

This brief presents a single-cavity dual-band filter based on stepped impedance resonators (SIRs). This filter consists of a dielectric cylinder, four SIRs and an inductive cross-coupling structure (ICCS) placed inside a rectangular metal cavity. Through eigenmode analysis, the proposed filter could generate four resonant modes in two working bands. The ICCS is employed to obtain transmission zeros. After optimization, a compact single-cavity dual-band filter with low insertion loss, high selectivity, wide working bandwidth and wide out-of-band suppression is designed at 2470–2700 MHz and 3340–3750 MHz. Measured results show that the proposed filter could provide a promising candidate for both LTE (Long Term Evolution) and 5G (the Fifth Generation) mobile communication systems.