New triple-passband bandpass filter with compact size

This paper presents a compact triple-band bandpass filter that involves using the embedded stepped impedance resonators (SIRs) for achieving simultaneously compact circuit size and good triple-band performance. The embedded SIR is designed to have two resonant paths at 1.575 GHz, 3.5 GHz and 5.2 GHz. The resonant frequencies can be easily controlled by tuning impedance ratio (K₁ and K₂) and length ratio (α₁ and α₂) for each resonant paths in the embedded SIR. This study provides an effective method to easily design the triple-passband filter with compact circuit size, high passband selectivity and low insertion loss.