Design of a dual-band filter with high selectivity and wide stopband

This paper proposes a design of dual-band bandpass filter with a high selectivity and a wide stopband, by using two ring type hairpin resonators. The equivalent circuit of the used resonator is analyzed through the analysis of odd and even modes. The designed filter can achieve dual passbands at 2.4 GHz and 3.65 GHz for wireless local area network (WLAN) and 5 G communication systems, with transmission zeros at 2.9 GHz and 5.1 GHz, realizing high selectivity. With a wideband bandstop filter on the input port, a wide stopband from 4.6 GHz to 17.3 GHz is realized.