A compact dual-band filter using S-shaped stepped impedance resonators

In this paper, we propose a compact dual band bandpass filter (BPF) using S-shaped stepped impedance resonators (SIRs). By appropriately selecting the impedance ratio of the SIR the harmonic frequencies can be tuned for generating the dual-passband response. Using this structure, the bandwidth of each passband can be controlled independently by adjusting the coupled spacing and coupled length. The BPF has good dual- passband performance at 2.4/5.2 GHz and has a very smaller area in comparison of previous works.