A novel open-loop DGS for compact bandstop filter with improved Q factor

A novel slot-shaped defected ground structure (DGS) on the microstrip line to provide a band-rejection property with an improved Q factor is proposed in this paper. It has a size of only 11% of conventional dumbbell DGS unit section and 26.8% of U sharp DGS unit section, while the Q factor is 7.6 times than dumbbell DGS and 3.2 times than U-sharp DGS at the same resonant frequency of 4.88GHz. A minimized two-pole bandstop filter based on the newly proposed DGS is designed and simulated. It has a 3dB cutoff frequency of 3.38GHz with 37dB rejection in the stopband from 3.63 to 3.75GHz, the size of the filter is less than 0.35 λg × 0.16 λg.