Equivalent-circuit analysis and lowpass filter design of split-ring resonator DGS

The equivalent-circuit of a split-ring resonator (SRR) defected ground structure (DGS) is investigated in this paper. The dependence of the transmission characteristic on the dimension of a split ring, such as side-length and split-gap, is analyzed in detail. In addition, an improved SRR DGS cell model with open stubs loaded on the conductor line is then presented to improve the out-band suppression. By using the equivalent-circuit analytical method, an S-band microstrip low-pass filter with perfect low-pass characteristic and high out-band suppression is designed and fabricated.