Wideband bandstop defected ground structure filter with enhanced common-mode suppression using split ring

An effective method to broaden the rejection bandwidth of dump-shaped defected ground structure (DGS) filter design is proposed in the paper. One traditional dumbbell-shaped DGS is split by using one split ring, and reconstructed into two different compact DGSs. The distance between both of the DGSs is so close that there exists mutual inductance, which can be utilized to broaden the rejection bandwidth effectively. The effect of different parameters of the split ring on the rejection bandwidth and depth of the filter is analyzed. Simulated results demonstrate that, with the same area of 5.5mm by 10 mm, rejection bandwidth of the proposed filter is from 4.4 GHz to 10.5 GHz for the common-mode noise (CM) while that of the traditional dumbbell-shaped DGS is from 5.3 GHz to 7.3 GHz. Compared to other schematics adopting multiple DGS to broaden bandwidth, it can broaden the bandwidth by dividing the existed DGS into multiple parts and reconstructing a new filter. The experimental results show good agreement with simulated results.