Abstract:A novel Split-Ring Resonator (SRR) Defected Ground Structure (DGS) is presented. Compared with the conventional dumbbell DGS, this structure has a sharp band-gap and flat low-pass characteristic. A detailed analysis of the equivalent circuit of the cell model and the relationship between physical sizes and electrical parameters is made. Then an improved SRR DGS cell model loaded with open stubs is proposed in order to improve the out-band suppression. Based on this structure, a compact S-band microstrip lowpass filter is designed and fabricated. The measured results show that, this filter has a low insertion loss of below 0.5dB and a high out-band suppression of more than 30dB.