Wideband bandpass filter integrating half mode substrate integrated waveguide with novel DGS cell

In this paper, two wideband bandpass filters are presented, which combines half mode substrate integrated waveguide (HMSIW) with a pair of face to face improved dumbbells defected ground structure (DGS) cells. The proposed DGS cell have a good sideband selectivity feature compared with the conventional dumbbell DGS . To validate the methodology, two filters, i.e., one-stage and three-stage,with center frequency of 8.85 GHz and 8.35 GHz are designed and measured. According to the measured results, the one-stage HMSIW-DGS filter has an insertion loss of 0.8 dB in passband, a 3 dB rejection bandwidth of 63%, and the three-stage HMSIW-DGS filter has an insertion loss of 1 dB in passband, a 3 dB rejection bandwidth of 40%, and a good sideband selectivity.