Design of Compact Quad-Band Bandpass Filter Using Stepped Impedance Resonators

In this paper, we presented the compact quad-band bandpass filter (BPF) using stepped impedance resonators (SIRs). The filter is designed to have quad-band at 1.2, 2.4, 3.5 and 5.2 GHz. The four pass bands are simultaneously generated by controlling the impedance and length ratios of the traditional and half wavelength stepped impedance resonators. The filter can provide the multi-path propagation to enhance the frequency response and achieving the compact circuit size. The measured results are in favourable agreement with the full-wave electromagnetic (EM) simulation results.